1200 words and three scholarly references

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Laura A.Freberg

John T. Cacioppo University of Chicago

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California Polytechnic State University, San Luis Obispo

Discovering Psychology

The Science of Mind

F O S T E R , C E D R I C 1 6 9 2 T S

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F O S T E R , C E D R I C 1 6 9 2 T S

Taste buds contained in the papillae of the tongue are far more responsive to bitter tastes than to sweet tastes.

F O S T E R , C E D R I C 1 6 9 2 T S

The Science of Mind

The Discipline of Psychology

1 Explain the subject matter that psychologists study, addressing the meaning of mind and psychology’s role as a hub science.

2 Analyze the respective contributions of philosophy and the physical sciences as the “roots” of modern psychology.

3 Compare and contrast the early movements in psychology—structuralism, Gestalt psychology, functionalism, behaviorism, psychodynamic theory, and humanism—in terms of leading figures, core principles, and contributions to modern psychology.

4 Differentiate the seven major perspectives of modern psychology in terms of typical research questions, research methods, and focal causes of behavior.

5 Analyze the ways in which the seven major perspectives can be integrated to address a single psychological problem or topic.

6 Explain why psychology’s role as a “hub science” allows psychologists to pursue a wide range of career paths with respect to professional specialties and research areas.

Learning Objectives

Studying the science of psychology can lead you to see yourself and other people in completely new

ways. A lifetime of observation teaches us many things about our own behavior and about the behavior of others,

but psychological science can uncover new and exciting explanations for behavior that we otherwise might miss. Let’s begin with a seemingly simple and familiar example: our ability to taste. We all know a lot about taste—what we like or dislike, the different qualities of taste, and so on. You might even be aware that some

types of taste seem stronger than others. Most of us can taste sweetness in a solution of one part sugar in 200

parts water; this ability shows an impressive taste

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 1 4

Introspection is the personal observation of our own thoughts, feelings, and behaviors. Because we are not perfect observers of the operations of our own minds, psychologists developed other methods that provide truly scientific insight into the mind. In this functional magnetic resonance imaging (fMRI) scan, areas of the brain that were activated when the participant was hungry are highlighted. Through technology, researchers can better understand how the brain regulates hunger. From D. Fuhrer, S. Zysset, & M. Stumvoll, “Brain

Activity in Hunger and Satiety: An

Exploratory Visually Stimulated fMRI

Study,” in Obesity (2008) 16: 945–950.

sensitivity, to be sure. As remarkable as this sensitivity appears to be, however, people can detect one part bitter substance (like quinine) in 2 million parts water. This contrast in taste sensitivity between sweet and bitter does not reflect the actual difference between sweet and bitter sub- stances—that is, bitter tastes are not 10,000 times stronger than sweet tastes, but that is how we experience them. Why would we have such a vast difference in sensitivity between these tastes?

Our observations of taste do not help us out much in answering this question, but psychology can. As it turns out, our greater sensitivity to bit- ter tastes is highly adaptive: Most poisons or toxins taste bitter, and if you want to stay alive, it is more important to avoid swallowing poison than to enjoy something sweet. Being far more sensitive to tastes that are bitter is a trait that has served our species well, because it helps us avoid eating things that could potentially kill us. Psychology helps us understand why

we do the things we do by providing a context for understanding behavior. To gain that understanding, psychology has to act like the zoom feature in Google Earth. In some parts of this textbook, we will be zooming in on human behaviors, like looking at the highly magnified image at the beginning of the chapter of the tongue, which allows us to taste, and tracing the messages about taste sent from the tongue to the brain. At other times, we’ll zoom back out again to take in the

larger picture, to better understand why the boy on the previous page is giv- ing his bitter-tasting broccoli a skeptical look. Psychologists zoom in to the study of the mind using in-depth per- spectives, which we will be describing in this chapter. For example, we can look at the little boy’s reaction to his broccoli from a developmental perspective, which tells us that taste sensitivity decreases over the life- span. Or, using the social perspective, we can think about social influences like culture on food preferences. Cottage cheese, enjoyed by many Ameri- cans, is viewed with disgust in some other parts of the world. Fruit bat pie, a delicacy in Palau, might not be a popular item for a campus dining facility in the United States. Although single perspectives can tell us a lot about a phenomenon like our sensitivity to bitter tastes, no one perspective can give us a com- plete answer. The best view of all comes from zooming back out again by putting multiple perspectives together into a whole. You can learn a lot about your house from Google Earth by zooming in, but when you see how your home fits into the larger scene of city, state, country, and planet, that viewpoint adds something special to your understanding. We’ll start by learning more about psy- chology’s main perspectives, along with a little background about their origins. At that point, we’ll be in a better position to understand how these perspectives come together to give us the big picture.

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT IS PSYCHOLOGY? 5

What Is Psychology? The study of the mind is as fascinating as it is complex. Psychological sci- entists view the mind as a way of talking about the brain and its activities, including thought, emotion, and behavior. A quick look at this textbook’s table of contents will show you the variety of approaches to mind that you will encounter along this voyage, such as the thinking mind (cognitive psy- chology) and the troubled mind (abnormal psychology).

The word psychology is a combination of two Greek words: psyche (or psuche), or “soul,” and logos, “the study of.” For the ancient Greeks, the use of the word “soul” was closer to our modern view of a spirit or mind. Logos is the source of all our “ologies,” such as biology, anthropology, and so on. Literally translated, therefore, psychology means “the study of the mind.”

Contemporary definitions of psychology refine this basic meaning. Most psychologists today define their field as the scientific study of behavior and mental processes—that is, the scientific study of the mind.

The phrase behavior and mental processes has undergone several changes over the history of psychology. Behavior refers to any action that we can observe. As we will see in our chapter on research methods, obser- vation has been an important tool for psychologists from the very early days of the discipline. Notice, too, that our definition does not specify whose behavior is to be examined. Although the bulk of psychology focuses on human behavior, animal behavior has been an essential part of the dis- cipline, both for its own sake and for the sake of comparison with human behavior.

The study of mental processes has been highly dependent on the meth- ods available to psychologists. Early efforts to study mental processes were generally unsatisfactory, as they relied on the use of introspection, or the personal observation of your own thoughts, feelings, and behaviors. Because it is difficult for others to confirm an individual’s introspections, this subjective approach does not lend itself well to the scientific method. If you say that you are feeling hungry, how can anyone else really know if your observation is accurate or not? In the last 30 years, however, revolutions in the methods used to observe brain activity have allowed psychologists to revisit the question of mental processes with much greater objectivity and success.

As you learn more about psychology, some conclusions will seem obvi- ous to you. After all, we already know a great deal about the mind from our own experiences. In other cases, the conclusions of psychological research might challenge your firmly held beliefs. You may be surprised to learn that having a “good cry” can make you feel worse instead of better, or that people are less likely to come to another person’s aid when they are part of a crowd of observers than when they are the only ones available to help. Sometimes, we even believe ideas that contradict each other. Everyone knows that opposites attract and that birds of a feather flock together. It takes the science of psychology to determine when and under what condi- tions these beliefs are actually correct.

mind The brain and its activities, including thought, emotion, and behavior.

psychology The scientific study of behavior and mental processes.

introspection Personal observation of your own thoughts, feelings, and behavior.

of the discciplinne. Notice, too,, that our definition does not spep cifyy se beehahaviv or iis to bbe examinedd. AlAlththooughgh tthhe buulk k ofo psysycholologogy fofocuseess umanan bbeehavvioior,r, aanimam l behahavvior has bbeen an eessssenentit alal parart ofof ttheh disis-- ne,, bboth for its owown saake andnd ffor ttheh ssaake of ccoompaarir sson n wiwith hhumumanan vivior.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY6

What Are Psychology’s Roots? Psychology is a relatively young discipline, dating back only to the 1870s. However, topics that interest modern psychologists go back much farther in the history of human thought. People living as long ago as 6000–5000 bce in Assyria described their dreams (Restak, 1988). Among these accounts are descriptions of being chased, which are still among the most common dreams experienced by people (Nielsen et al., 2003). See ● Figure 1.1 for common dream themes that many people experience.

The psychology family tree includes two major roots: philosophy and the physical sciences. Psychologists answer questions traditionally posed by philosophers by borrowing the methods of the physical sciences. We examine scientific methods in detail in our next chapter.

Philosophers and psychologists share an interest in questions regarding the nature of the self, the effects of early experience, the existence of free will, and the origin of knowledge. Both disciplines consider the relative bal- ance of biological factors (nature) and environmental factors (nurture) in the resulting human behavior. Both attempt to determine the relationships between self-interest and the welfare of the community, between body and mind, and between humans and the other species with whom we share the planet. Although we typically consider questions of the unconscious mind

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F i g u r e 1 . 1

philosophy The discipline that systematically examines basic concepts, including the source of knowledge.

physical science Any science that studies nonliving matter, including physics, chemistry, astronomy, and geology.

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT ARE PSYCHOLOGY’S ROOTS? 7

and abnormal behavior to be the realm of the psychologist, philosophers investigated these issues thousands of years before the first psychologist was born.

The Philosophers’ Questions

A comprehensive survey of the philosophical roots of psychology is beyond the scope of an introductory textbook like this one, but we can

provide you with a small sample of this heritage. The point we would like you to take away from this discussion is that many of the ques- tions you will read about in this textbook are not unique to psychol- ogy, but have fascinated thinkers for thousands of years. What is the mind? What is the relationship between the body and mind? Is the mind inborn or is it formed through experience?

The ancient Greek philosopher Plato (427–347 bce) was one of the earliest thinkers to tackle the question “What is the mind?” Plato’s version of the mind featured three parts that must be in balance: reason, spirit, and appetite. He compared these parts to a team of horses (spirit and appetite) guided by a driver (reason). Plato’s division of the mind is echoed in the more modern work of Sigmund Freud (1856–1939). Freud also divided the mind into three parts: the id (inborn aggressive and sexual impulses), the ego (the self ), and the superego (conscience). Later in this textbook, we will see that Freud’s concept of the ego serves the role of Plato’s driver, oversee- ing and balancing the two horses: the impulses of the id and the restrictions imposed by the superego. You might relate to the dilemma of the driver (reason/ego) when you are faced with an opportunity to indulge an impulse (id) while hearing that little voice in the back of your head (superego) tell- ing you that this really isn’t a very good idea.

Another question with ancient roots asks about the relationship between body and mind, a topic that we will explore further in our chapter on biological psychology. On one side of the question were thinkers who believed in dualism, or the idea that body and mind are quite different and separate. To the dualist, our bodies are physical, but our minds are some- thing nonphysical and somewhat more mysterious. Arguing against this point of view were the proponents of monism, the idea that mind and body are not separate. Another way of thinking about monism is to assume that the mind is the result of activity in the brain. Does one of these positions seem closer to your own way of thinking than the other?

The ancient Greek philosophers were nearly evenly split between monism and dualism. Democritus (460–370 bce) and Aristotle (384–322 bce) argued in favor of monism, while Pythagoras (580–500 bce), Socrates (469–399 bce), and Plato believed in dualism. As the classical world of Greece and Rome gave way, monism moved to the background while medi- eval Christian thinkers wrote about a dualism between body and soul. Dual- ism continued to dominate discussion during the Renaissance. The French philosopher René Descartes (1596–1650) was a vocal proponent of dualism. He saw the body as mechanical but the mind as a nonphysical entity not suit- able for scientific inquiry.

Plato viewed the mind as a charioteer (reason) driving two horses (spirit and appetite).

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY8

Contemporary scientists studying the brain support monism, but they agree with Descartes’ belief that the mind and body influence one another. In our biological psychology chapter, we emphasize the reciprocal rela- tionships between biology and behavior. Our biology clearly impacts our behavior, as when hormones released during times of stress increase our heart rate and make our palms sweaty, but our behavior also affects our biology, as the situations we choose to enter (e.g., skydiving) influence the release of stress hormones. This reciprocal influence between biology and behavior can be seen in social situations, too. We know that among primates, males’ testosterone levels predict their amount of sexual activity. At the same time, however, the males’ testosterone levels increase in the presence of larger numbers of available and receptive females (Cacioppo & Berntson, 1992). That is, the social context affects the physiology of the male primates.

Just as philosophers disagreed about the relationship of mind and body, they argued about whether the mind’s knowledge was inborn or the product René Descartes (1596–1650) believed

in mind-body dualism, or the separation of the physical body from the nonphysical mind.

Psychology as a Hub Science

Psychology Connects to Other Disciplines

sychology is all about peo- ple, and there are very few

occupations that do not require an understanding of people and their behavior. An architect can- not design a functional space without

considering how people respond to crowding. An attorney cannot cross- examine a witness without an under- standing of memory, motivation, emotion, and stress. A teacher can- not encourage students to reach their potential without an understanding of child development. The study of psychology, then, provides you with better insight into and understanding of many different occupations and fields of study.

You have probably seen applica- tions that allow you to map your friendship networks on social media, with shorter links indicating greater connectivity than longer links and

with larger bubbles indicating more overlapping friendships with another person. Kevin Boyack and his col- leagues generated a similar map of the sciences (see ● Figure 1.2), but used reference lists in journal articles instead of friendship networks (Boy- ack, Klavans, & Börner, 2005). The resulting analysis shows that psychol- ogy is one of the major “hub” sci- ences, with strong connections to the medical sciences, the social sciences, and education. In our upcoming chapters, we will highlight these con- nections with examples that are rel- evant to each particular chapter.

Sociology

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International Relations

History Economics

GeographyPsychiat

Management

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Library and Information Sciences

Psychology Public Health

Ophthalmology

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT ARE PSYCHOLOGY’S ROOTS? 9

John Locke (1632–1704) and other empiricist philosophers believed that the mind was a “blank slate” at birth and that knowledge was gained through experience.

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Psychology as a Hub Science. This map of science was generated by comparing citations from over 1 million papers published in more than 7,000 journals since 2000. Psychology appears among the seven major areas of science, indicated in the map by large fonts. The other six major areas are social sciences, mathematics, physics, chemistry, earth sciences, and medicine. Source: Adapted from “Mapping the Backbone

of Science,” by Kevin W. Boyack

et al., 2005, Scientometrics, 64(3).

With kind permission from Springer

Science+Business Media.

F i g u r e 1 . 2

of experience. Some philosophers, including Descartes, argued that ideas and emotions were innate or inborn. More commonly, philosophers begin- ning with Aristotle believed that all knowledge is gained through sensory experience. Beginning in the 17th century, this idea flourished in the Brit- ish philosophical school of empiricism. The empiricists viewed the mind as a “blank slate” at birth that was filled with ideas gained by observing the world. As one of the major empiricists, John Locke (1632–1704), wrote in An Essay Concerning Human Understanding:

Let us then suppose the mind to be, as we say, white paper void of all characters, without any ideas. How comes it to be furnished? . . . To this I answer, in one word, from EXPERIENCE. (Locke, 1690, II.1.2)

Empiricism contributed two important ideas that continue to influence contemporary psy- chologists. First, empiricism is the founda- tion for science itself, which allows us to gain knowledge through careful and systematic observation, resulting in “empirical” results.

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Aristotle (384–322 BCE) argued in favor of monism and believed that we gain knowledge through our senses.

John Locke (1632–1704) and other emppiricist pphiloosopophehers believeved thaat the mminindd wawass a “blaannk slate”” aatt bibirtr h anndd ththatat knnowlededgge wwasas ggaia nedd throuughh experieencce.

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY10

Second, empiricism guided the 20th-century behaviorists, psy- chologists who examined behaviors that were the result of expe- rience and that could be directly observed. The behaviorists’ contributions to psychology will be discussed in detail in our chapter on learning.

The philosophical debate about the source of knowledge is echoed in psychology as researchers consider the relative con- tributions of inborn or innate factors (nature) and experience (nurture) to particular behaviors. You might have heard people debate the importance of genes (nature) or good schools (nur- ture) on shaping the intelligence of children, a topic we discuss in a later chapter on cognition and intelligence. Contemporary

psychology no longer views the question of nature and nurture as either/or. Instead, we see the mind as a result of complex interactions between inborn characteristics and experiences. We might have a genetic predisposition for intelligent behavior, but intelligence depends on experience, too. During the 1970s, children in Romanian orphanages experienced extremely deprived social conditions due to a lack of fund- ing for their care. The children had few oppor- tunities to interact with other people or with the environment. They spent most of their days in cots surrounded by sheets, preventing them from even seeing other children. Children who were adopted from these orphanages at young ages were able to recover, but the children who had endured years of deprivation experienced

permanent cognitive deficits (Ames, 1997). In our chapters on genetics and development, we will revisit these debates in depth.

If philosophers and psychologists ask the same questions, what makes these two fields different from each other? As we noted earlier, the struc- ture and operations of the mind are not always obvious, even to the most brilliant philosopher, and the scientific methods of the psychologist helped develop additional theories of the mind and behavior. The branching of psychology from philosophy was gradual. Nineteenth-century philoso- phers began to argue for the experimental study of human behavior, and some, like Alexander Bain (1818–1903), wrote psychology textbooks and founded psychology journals. As philosophical ideas were tested scientifi- cally, new explanations for the mind and behavior began to emerge, and the march toward psychological science as an independent discipline became irreversible.

The Physical Scientists’ Methods

Running along a parallel track to the early philoso- phers, ancient physicians were laying the founda- tion of our biological knowledge of the brain and nervous system, discussed in greater detail in our

chapter on biological psychology. During this pursuit, physicians helped

The empiricists had a profound influence on the foundations of American political thought—All of us are created equal. For generations, Europe had been ruled by people who were born into positions of power instead of earning the privilege of leading through hard work and education. If knowledge is not innate or inborn, any of us can learn enough to grow up to be President.

Desperate conditions in Romanian orphanages in the 1970s left many children without the experiences they needed for optimum cognitive or social development.

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develop the scientific methods that would become cen- tral to contemporary psychology and previewed the application of the knowledge they gained to the improvement of individual well-being.

Although some confusion occurred along the way, as in Aristotle’s belief that the mind was located in the heart, ancient people had a rudimentary understand- ing that the head and later the brain were important for mental life. As long as 7,000 years ago, healers using a technique known as trepanation drilled holes in a person’s skull to cure some unspecified conditions, possibly headache or hallucination. Subsequent growth of the skull bones indicates that some patients actually survived this procedure. The early Egyptians correctly understood that paralysis of a part of the body was due to brain damage and that such damage was permanent (Breasted, 1930).

As early as 500 bce, Greek physicians began to systematically dissect human bodies. Not only did they correctly conclude that the brain was the organ of memory, thinking, and understanding, but they noticed the con- nection of the brain to the sense organs, such as the eyes, and recognized that the brain is the source of many emotional problems. Later Greek phy- sicians offered a rudimentary theory of personality that remained popular until the 19th century. According to this approach, personality would be affected by the relative amounts of four different body fluids: yellow bile (a type of gastric fluid), black bile, blood, and phlegm. For example, a person with a sad disposition suffered from excess black bile, whereas a person with a lot of blood would be cheerful. Medical practices such as “bleeding” a patient were applications of this theory.

For many centuries, the whole of medicine remained a primitive busi- ness. Beginning in the 17th and 18th centuries, scientists armed with new technologies, including the light microscope (see ● Figure 1.3), began to make a series of important new discoveries about the human body and mind. For example, they demonstrated that a single sensory nerve carried one type of information, instead of multiple types. You might have already duplicated this research yourself while rubbing your sleepy eyes—you see a flash of light. The nerves serving the retina of the eye do not know how to process information about touch or pressure. When stimulated, they are capable of one and only one type of message—light. These types of discoveries about the physical aspects of the mind convinced scientists that, contrary to Descartes’ conclusions, the mind really could be studied scientifically.

The work of Hermann von Helmholtz (1821–1894) on the speed of nerve signaling provided further evidence that the mind had a physical basis. Von Helmholtz asked his participants to push a button when they felt a touch. If a thigh were touched, participants reacted faster than when the toe was touched. Because the toe is farther from the brain than the thigh, signals from the toe required more time to reach the brain. Von Helmholtz used these differences in reaction time to show that voluntary behavior did

Ancient people might have attempted to cure headaches, seizures, or psychological disorders by drilling holes in the skull. Bone growth around the hole indicates that some of these patients survived the procedure.

The traditional red-and-white barber’s pole has its roots in the practice of bloodletting to treat diseases, which was often carried out in barber shops. The red-and-white stripes represent bloody bandages wrapped around a pole.

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY12

not occur instantaneously as previously thought. The fact that behavior is not instantaneous, but requires time for the system to process physical signals, contributed to a more scientific, less mystical view of the nervous system.

At the same time that the philosophers began to incorporate physi- ological and psychological concepts into their work, the physical scientists began to explore the questions asked by the philosophers. The gradual merger of these approaches resulted in a series of experiments that looked more and more like contemporary psychology. Scientists began to ask questions about the relationships between physical stimulation and its resulting sensations. For example, Gustav Fechner (1801–1889) was able to identify the softest sound a person could hear by randomly presenting sounds of different intensities, to which a participant would respond “yes” or “no.” When the “yes” responses reached 50%, Fechner concluded that the sound was within the range that the human ear could detect. The stage was set for a modern science of psychology.

The work of Hermann von Helmholtz (1821–1894) on reaction time helped establish the mind as something that could be studied scientifically.

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Microscopes Changed the World of Science. This light microscope was used by Anton von Leeuwenhoek to discover red blood cells in 1676. Microscopes opened a whole new world to scientists interested in living things.

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WHAT ARE PSYCHOLOGY’S ROOTS? 13

Summary 1.1 Highlights in the Philosophical and Scientific Roots of Psychology

Person or group Things to remember Ancient physicians The brain is the source of the mind.

Ancient Greek philosophers Provided natural, not supernatural, explanations for their observations.

Descartes Mind-body dualism.

British empiricists Knowledge is the result of experience.

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17th- and 18th-century physical scientists

Discoveries about sensation and movement showed that the mind was physical.

Von Helmholtz Studies of reaction time reinforced the idea of the mind as physical.

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY14

How Did the Science of Psychology Begin? As psychology developed from the gradual merger of philosophical ques- tions and scientific reasoning, the young discipline struggled to determine which questions and methods were best suited to its goals. Lively debates arose among psychologists who helped to shape the field.

Wilhelm Wundt and Structuralism

The credit for being the first psychologist goes to Wilhelm Wundt (1832–1920), who conducted the first documented psychological experiment in his laboratory at the University of Leipzig in 1879. This

landmark experiment was a simple test of reaction time. How quickly after hearing a ball drop onto a platform could a person respond by striking a telegraph key?

Wundt, trained in medicine and physiology, was one of the physical scientists who became interested in the mind. Wundt believed that the

goal of a new science of psychology was to understand consciousness, which we discuss in a later chapter.

Wundt saw mental experience as a hierarchy. The mind constructs an overall perception (the food I’m eating tastes good) out of building blocks made up of separate sensations (such as taste or vision) and emotional responses. One of Wundt’s students, Edward Titchener (1867–1923), expanded on Wun- dt’s views to establish a theory of structuralism, in which the mind could be broken down into the smallest elements of mental experience. Titchener’s approach to psychology paralleled the general trends in the physical sciences of his day, such as efforts in chemistry to break molecules into elements and attempts by physicists to describe matter at the level of the atom.

Both Wundt and Titchener employed introspec- tion as an experimental technique, but they meant somewhat different things when they used the term. Recall that we earlier defined introspection as observ-

ing your own thoughts, feelings, and behaviors. Wundt’s approach to introspection is illustrated by his reaction time experiment with the falling ball. This experiment is introspective in the sense that pressing a telegraph key indicates an internal state—I heard the ball fall. Titchener’s approach to introspection was more consistent with the building block approach to experience. He would instruct his research participants to describe an object, perhaps a cup, in great detail (size, color, shape, and so on), hoping that these details would serve as the building blocks for the mind’s overall perception of the cup.

Wilhelm Wundt (1832–1920), seated in this photo, is considered to be the first experimental psychologist.

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consciousness, which we discuss in a later chapte WuW nddtt saw w mementn al eexpxperiencnce e asas a hhieierara

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HOW DID THE SCIENCE OF PSYCHOLOGY BEGIN? 15

Gestalt Psychology

The structuralists’ effort to break behavior down into its essential elements was rejected by a group of early 20th-century German psychologists, including

Kurt Koffka, Max Wertheimer, and Wolfgang Köhler, who founded Gestalt psychology. Gestalt, although lacking a clear translation into English, means “form” or “whole.” The Gestalt psychologists believed that breaking a “whole” perception into its building blocks, as advocated by the structur- alists, would result in the loss of some important psychological informa- tion. For example, take a look at the middle image in ● Figure 1.4. It is the same in both the top and bottom rows, yet in the context of the first row, most people would interpret the image as the letter B. In the context of the bottom row, however, the image looks like the number 13. The structural- ists would have a difficult time explaining why the same visual building blocks could lead to such different conclusions.

While largely known for their work in perception, the Gestalt psycholo- gists also had wide-ranging interests in learning, memory, motivation, and group dynamics. The influence of Gestalt psychologists will resurface in our later discussions of perception and cognitive psychology, the study of thinking and information processing.

William James and Functionalism

While the structuralists and Gestalt psychologists continued their debate, a new type of psychology emerged, partly in response to the publication of Charles Darwin’s The Origin of Species in 1859 and

The Descent of Man in 1871. Functionalism viewed behavior as purpose- ful, since it led to survival. Nineteenth-century United States politics and culture, which valued individuality, practicality, and frontier survival, embraced functionalism. Instead of restricting themselves to exploring the

Max Wertheimer (1880–1943) was one of the founders of Gestalt psychology.

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Gestalt Psychologists Challenged Structuralism. Participants usually see the middle figure as a B when instructed to look at the first row, but see a 13 when instructed to read the second row. The structuralists, who believed that experiences could be reduced to small building blocks, would have difficulty explaining these results. In contrast, Gestalt psychologists, who emphasized the role of context or the “whole” in perception, would have no difficulties at all.

F i g u r e 1 . 4 Gestalt psychology An approach to psychology that saw experience as different than the sum of its elements.

functionalism An approach to psychology that saw behavior as purposeful and contributing to survival.

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY16

structure of the mind, functionalists were more interested in why behavior and mental processes worked in a particular way. To answer these ques- tions, functionalists broadened their research techniques beyond the intro- spection used by Wundt and Titchener.

Functionalism’s chief proponent was William James (1842–1910), whose textbook, Principles of Psychology (1890), dominated the field of psychology for 50 years. At Harvard University, James offered a course in psychology and established a laboratory in 1875, four years before Wundt’s first lab. However, James’s lab served primarily as a demonstration lab for his course rather than a research lab like Wundt’s. Because of psychology’s emphasis on research contributions, Wundt is still given credit for being the first psychologist.

There are few topics in psychology that James did not address in his Principles, and many of his ideas sound thoroughly modern. For example, James coined the term stream of consciousness to describe the flow of ideas people experience while awake. Throughout his discussions of mental pro- cesses and behavior, James emphasized the role of evolution. For the func- tionalist, the value of an activity depended on its consequences. Behaviors that enhance survival are repeated, and those that are either irrelevant

he Gestalt movement traces its origin to a single

experiment conducted by Max Wertheimer in 1912 that demon- strated the apparent movement of objects (Wertheimer, 1912). According to historians, Wert- heimer was inspired to conduct his study after playing with a toy strobo- scope, which he bought from a ven- dor at a train station (Boring, 1942). If you look through the slits in the rotating disk of a stroboscope, like the one in ● Figure 1.5, It looks like the images behind the disk are mov- ing, somewhat like an old cartoon. Most of us would probably just enjoy

the toy, but Wertheimer immediately saw a deeper meaning, which he tested in his experiment.

The Question: Can the perceived movement between two stimuli be explained in structuralist terms? If Wundt and the structuralists were correct and all perceptions could be broken down into their elements, then we would not “see” movement when viewing stationary stimuli.

METHODS Wertheimer used a stroboscope to control the timing of the appearance of two black lines (one vertical and

the other horizontal) against a white background. The first line would appear and then disappear, followed some time later by the appearance and disappearance of the second line. The amount of time between the disappearance of the first line and the appearance of the second, which depended on the speed with which the wheel on the stroboscope was turned, varied from trial to trial, and the observers noted whether they perceived movement or not.

RESULTS When the interval between the appearance of the two lines was

The Experiment That Launched Gestalt Psychology

Connecting to Research

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HOW DID THE SCIENCE OF PSYCHOLOGY BEGIN? 17

about 30 milliseconds (a millisecond is one one-thousandth of a second), the observers reported that the lines appeared and disappeared together. With intervals longer than 60 mil- liseconds, observers reported seeing one line that moved from a vertical to horizontal orientation.

CONCLUSIONS Wertheimer realized that his par- ticipants were “seeing” something— movement—that could not be explained by the sensations of lines appearing and disappearing. Wundt and the structuralists must be wrong— there is more to perception than just sensing elements, like lines. An appli- cation of Wertheimer’s work can be seen in the “moving” words in scroll- ing electric signs, which are really just groups of lights flashing on and off.

Mary Whiton Calkins (1863–1930) was a student of William James at Harvard, although she could not officially register due to her gender. She studied memory and the self and served as president of the American Psychological Association in 1905.

A Toy Stroboscope Helped Launch Gestalt Psychology. Studying a toy stroboscope, which produces a perception of movement, inspired Wertheimer to question Wundt and the structuralists. How could the perception of movement in the image be explained by basic sensations if there were no real sensations to see in the first place?

F i g u r e 1 . 5

or damaging to survival are abandoned. If we dream, it must be because dreaming improves our chances of survival. If we enjoy ice cream, it must be because eating sweet, high-fat foods enhances survival—at least it did for our ancestors, for whom famine was a much more likely problem than obesity.

It is difficult to overestimate the impact of William James on psychol- ogy. Although he really didn’t establish a particular “school” or train large numbers of students as did Wundt or other early psychologists, James’s ideas have become so dominant in psychology that we no longer refer to any separate “functionalist” approach. Structuralism came and went, but all contemporary psychologists are generally functionalists at heart. As described by psychology historians, “As a systematic point of view, functionalism was an overwhelming success, but largely because of this success it is no longer a distinct school of psychology. It was absorbed into the mainstream psychology. No happier fate could await any psychological point of view” (Chaplin & Krawiec, 1979, p. 53).

James, like the Gestalt psychologists, rejected the notion that you can study the mind by breaking it into elements or building blocks, as this division would result in a loss of understanding. As psychology entered the 20th century, this “big picture” approach of William James eventually broke up into a variety of sep- arate perspectives, as psychologists attempted to gain understanding by limiting their research to particular aspects of the mind and behavior.

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY18

The Behaviorists and the Cognitive Revolution

Beginning at the dawn of the 20th century, the “mental processes” in our definition of psychology took a backseat to observable behavior for the bet- ter part of the next 50 years, as psychologists follow- ing the perspective of behaviorism concentrated on

observable, measurable behaviors. As part of their effort to measure behav- ior carefully, many behaviorists restricted their research to studies using animals. Armed with Darwin’s evidence linking humans to animals, the behaviorists comfortably drew parallels between their observations of ani- mals and their assumptions about human behavior. In particular, behavior- ists were fascinated by learning, which we define as any persistent change

in behavior due to experience. We will examine the behaviorists’ contributions to this area in depth in a later chapter on learning.

Ivan Petrovitch Pavlov (1849–1936) had a par- ticularly significant impact on the course of behav- iorism and psychology. While studying digestion in dogs, he realized that the dogs’ salivation in response to the arrival of the handler or to being harnessed for an experiment indicated that the dogs had associ- ated, or linked, these signals with the arrival of food. The dogs’ ability to use this learned association to anticipate important future events was a remarkable advantage in terms of survival. This type of learning is now referred to as classical or Pavlovian condition- ing, which we will discuss in detail in our chapter on learning.

Psychology textbooks would not spend too much time on Pavlov if his research applied only to sali- vating dogs. Although classical conditioning occurs in rather primitive organisms, including fruit flies, snails, and slugs, it also occurs quite frequently in humans. Many of our emotional responses associ- ated with environmental cues are the result of this type of learning. If you feel especially anxious prior

to taking an exam, you can thank classical conditioning. If you are repulsed by the idea of eating a food that you once consumed just before becoming ill, this is again a likely result of classical conditioning. A war veteran who experiences distress while filling a pickup truck with diesel fuel (a common battlefield smell) is also likely to be experiencing the results of classical conditioning.

John B. Watson (1878–1958) began experimenting with learning in rats, and independently came to many of the same conclusions as Pavlov. Watson also echoed the “blank slate” approach of the British empiricist philosophers in his emphasis on the role of experience in forming human behavior. In a famous speech given in 1926, Watson made the following claim:

Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at

While studying digestion, Ivan Pavlov (1849–1936), seated second from left, realized that his dogs could learn that certain signals meant food was on the way.

behaviorism An approach to psychology that features the study and careful measurement of observable behaviors.

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HOW DID THE SCIENCE OF PSYCHOLOGY BEGIN? 19

Classical conditioning helps us understand the links we make between environmental cues and our emotions. If a soldier associated the smell of diesel fuel with traumatic experiences, smelling diesel fuel at a gas station back home can trigger distress.

John B. Watson (1878–1958) was a strong believer in the “blank slate” approach of the earlier empiricist philosophers. After working as a psychology professor, he applied his knowledge of human behavior to advertising.

Watson applied his understanding of behaviorism to advertising with great success. He believed that a product would sell better if it were paired with an appealing image.

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random and train him to become any type of specialist I might select—a doctor, lawyer, artist, merchant-chief, and yes, even into beggarman and thief, regardless of his talents, penchants, tendencies, abilities, vocations and race of his ancestors. (Watson, 1925, p. 10)

Later in Watson’s career, he applied his understanding of behavior to the budding American advertising industry. By 1930, Watson was earning $70,000 per year as an advertis- ing executive, an astronomical salary for the time and quite different from the $3,000 per year he earned as a professor. After discovering that blindfolded participants couldn’t tell the difference between brands of cigarettes, Watson con- cluded that to be successful, a product must be associated with an appealing image. The advertising industry was never the same, and today’s advertisers continue to apply Watson’s principles. Old Spice aftershave achieved great success with its ads featuring NFL wide receiver Isaiah Mustafa, implying that using Old Spice would make a man more “manly.”

Watson’s legacy in psychology was enormous. He changed the goal of the discipline from Wundt’s desire to understand consciousness to the prediction and control of behavior. He also restricted psychology to the study of observable behavior. As we will see in our section on research methods and throughout this text, even those psychologists who are inter- ested in internal events, like the visual recognition of an object, seek related observable behaviors, such as brain images, reaction time, or other similar measures.

Like Pavlov’s, Watson’s approach to psychology focused on the relationships between environ- mental cues and behavior. Other behaviorists were much more interested in the effects of consequences on behavior, an idea that was derived from basic functionalism. Edward Thorndike (1874–1949) proposed a law of effect, which suggested that behaviors followed by pleasant or helpful outcomes would be more likely to occur in the future, whereas behaviors followed by unpleas- ant or harmful outcomes would be less likely to occur. Thorn- dike based his law on obser- vations of cats’ behavior in a puzzle box he had constructed (see ● Figure 1.6). To escape the box, a cat was required to complete a sequence of behaviors. Through trial-and- error learning, the cat would escape faster and faster on

Joohnhn B. Watson (1878–1958 sstrongng believer in the “bla aapa prproach of the earlier em

iction and contrrol of behavior. He also restricted ppsyychologgy y to the y of oobsbsere vaable beb havior. AsAs wwe wwill see in ouour r secctiion n onon resesearch h hodss anand d throougughhoutut this teextxt, even thohosese ppsychcholologogisstts wwhho aarere interer- d inn iintn ernal evenntsts, likeke the vvisisuau l rer coognnition ofof an obobjectt, , seseek reelatateded rrvabblele behaviorsrs,, suuchch as brain imimages, reaction time, or otheherr simiillar surures. ike PPava loov’s,, Watsoon’s approaachh to pspsycychoholologygy

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY20

successive trials. In other words, the cat repeated effective behaviors and abandoned ineffective ones.

Like Thorndike, B. F. Skinner (1904–1990) was very interested in the effects of consequences on how frequently behaviors were performed. Skinner shared Watson’s belief that psychology did not benefit from any consideration of consciousness or internal mental states. Skinner believed that inner, private states such as thinking and feeling existed, but he viewed them as behaviors that followed the same rules as public behaviors, like driving a car (Jensen & Burgess, 1997). He not only reduced his study of behavior to the actions of rats and pigeons in adapted cages that came to be known as Skinner boxes, but he was very comfortable generalizing from the behavior of rats and pigeons to complex human behaviors. In spite of its strong focus on a limited set of animals and situations, Skinner’s behavior- ism has provided a wealth of beneficial applications. Smokers attempting to quit, doctors and nurses engaged in self-paced continuing education courses, and children receiving treatment for autism are all likely to be benefiting from Skinner’s efforts.

By the 1950s, the behaviorists’ disinterest in mental states and activity was challenged by scientists from diverse fields, including linguistics and computer science, leading to a cognitive revolution. Cognition covers the very private and internal mental processes the behaviorists avoided study- ing—information processing, thinking, reasoning, and problem solving. Ulric Neisser (1928– ) gave the new field its name in his 1967 book, Cogni- tive Psychology (Neisser, 1967).

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F i g u r e 1 . 6

B. F. Skinner (1904–1990) was interested in the effects of reward and punishment on future behavior.

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HOW DID THE SCIENCE OF PSYCHOLOGY BEGIN? 21

Breakthroughs in computer technology allowed these new cognitive psychologists to use mathematical and computer models to illuminate the mental processes leading to observable behaviors. Alan Newell (1927– 1992) and Herbert Simon (1916–2001) wrote groundbreaking artificial intelligence programs using human information processing as their model. The hardware of the computer was viewed as a metaphor for the brain, and its software mirrored the brain’s activity. By the 1980s, most university psychology departments were offering courses in cognition. By the 1990s, collaborations between cognitive and biological psychologists led to the new field of cognitive neuroscience, which seeks to identify brain struc- tures and functions involved in processing information. In a later chapter on cognition, language, and intelligence, we will explore more detail about the contributions of cognitive psychologists in more detail.

To illustrate how the behaviorist and cognitive approaches differ, we can take a look at how each explains language learning by children. Behav- iorists like Skinner believed that children acquired language in response to feedback, such as parental approval or being understood. In contrast, linguist Noam Chomsky proposed that human beings are born with innate mechanisms for learning language, which is exactly the type of specialized internal mental processing Skinner rejected. As we will see in our chapters on development and cognition, the cognitive approach to language learn- ing dominates our current understanding.

In contemporary departments of psychology, behaviorist approaches are represented by professors and researchers specializing in learning, who continue to explore the nuances of the effects of experience on behavior. Many of the big questions tackled by behavior- ists are now examined through the lens of the cognitive or biological perspective. Behavioral approaches make important contributions to real-world problems, including how best to pay employees and the treatment of psychological disorders and addiction.

Clinical Roots: Freud and the Humanists

With the excep- tion of occasional bursts of insight from the ancient

Egyptians and Greeks, the most common view of psychological disorders over the course of history has been the supernatural approach. According to this view, psychological disorders resulted from the actions of evil spirits or other external, magical forces. Although improvements in science and medicine led to more natural than supernatural explanations of psycho- logical disorders, effective treatments were not rapidly forthcoming. Patients in the 17th and 18th centuries were often subjected to bizarre treatments, including being spun around in a chair. As recently as the 1940s, patients with schizophrenia were regularly experimented on. They were subjected to questionable techniques such as “insulin shock therapy,”

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Ulric Neisser (1928– ) contributed the term cognition to the emerging field that studied information processing, thinking, reasoning, and problem solving.

Computers were named after the job title of the women who did most computation tasks before the machines were invented and who continued to operate them. Although these early computers were less powerful than your cell phone (not to mention much more expensive), their operation gave psychologists new ideas about how the mind might process information.

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY22

in which insulin injections led to comas, and were restrained in lukewarm baths. We discuss schizophrenia and its treatment in more detail in our chapters on psychological disorders and therapies.

Between the 17th and 19th centuries, supernatural explanations for psychological disorders began to give way to two scientific approaches: a medical model and a psychological model. The medical model of psy- chological disorder emphasized physical causes of abnormal behavior and medical treatments, such as medication. The psychological model sug- gested that abnormal behavior can result from life experiences, leading to fear, anxiety, and other counterproductive emotional responses. Psy- chological treatments take many forms, from offering support to applying cognitive and behavioral methods to help people think and problem solve in new ways. As we will see in our chapters on psychological disorders and therapies, contemporary psychologists typically combine these approaches to understand disorders and develop effective treatments. For example, we

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William James publishes Principles of Psychology.

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Edward Thorndike describes his Law of Effect.

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Photos, left to right: © INTERFOTO/Alamy; Library of Congress/Photo Researchers, Inc.; The APA logo is a trademark of the American Psychological Association. Reproduced with permission. No further reproduction or distribution is permitted without written permission from the American Psychological Association; © Mary Evans Picture Library/The Image Works; © Elias Goldensky, University Archives/University of Pennsylvania. Reproduced with permission; Courtesy of the Wellesley College Archives; Courtesy Special Collections & Archives, Truman State University; The Alan Mason Chesney Medical Archives of The Johns Hopkins Medical Institutions; Reproduced with permission of Mental Health America

F i g u r e 1 . 7

Milestones in the History of Psychology.

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HOW DID THE SCIENCE OF PSYCHOLOGY BEGIN? 23

know that feeling depressed has both physical components (changes in the activity of chemical messengers in the brain) and experiential components (exposure to stressful situations). Treatment for depression often combines medication with efforts to change the way a person thinks about his or her situation.

Sigmund Freud Sigmund Freud (1856–1939) built a bridge from his med- ical training as a physician to his belief in the impact of life experiences on behavior. His psychodynamic theory and its applications to the treatment of psychological disorders dominated much of psychological thinking for the first half of the 20th century. Freud managed to combine and commu- nicate ideas about the existence of the unconscious mind, the development of sexuality, dream analysis, and psychological roots of abnormal behavior in such a way that his theories influenced not just psychology but culture. He nearly single-handedly founded the study of personality in psychology,

The work of Sigmund Freud (1856–1939) on consciousness, sexuality, abnormal behavior, and psychotherapy played a dominant role in psychology during the first half of the 20th century.

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John B. Watson publishes Psychology as the Behaviorist Views It.Views It.

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The first Gestalt journal is published in Germany.

Jean Piaget publishes Judgment and Reasoning

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j ished in Germany.

Jean Piaget publishes Judgment and Reasoning

in the Child.

Hans Berger invents the electroencephalogram (EEG), still used today to study brain activity.

Carl Rogers introduces Humanist approaches to therapy.

Hans Berger invents

B.F. Skinner’s The Behavior of Organisms contributes to the dominance of behaviorism.

Carl Rogers introduces

The Boulder Conference establishes the scientist-

practioner model of clinical psychology.

Gordon Allport, a social psychologist, publishes The Nature of Prejudice. Wilder Penfield publishes the results of his observations of patients undergoing surgery for epilepsy.

George Miller’s “The Magical Number Seven, Plus or Minus Two” stimulates work in Cognitive Psychology.

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George Miller’s “The Magical Number Seven, Plus or Minus Two” stimulates work in Cognitive Psychology.

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Richard Dawkins’s The Selfish Gene popularizes

Evolutionary Psychology.

Photos, left to right: Ferdinand Hamburger Archives, Sheridan Libraries, John Hopkins University; Courtesy of the Moorland-Spingarn Research Center, Howard University Archives; © Farrell Grehan/CORBIS; © VEM/Photo Researchers, Inc.; © Nina Leen/Time & Life Pictures/Getty Images; © Michael Rougier/Time & Life Pictures/Getty Images; © Jon Roemer; Miller, George A. The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63(2), 81–97. doi: 10.1037/h0043158; © Dennis Van Tine/Retna Ltd./Corbis

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY24

and we will explore his theories more fully within that context. He devel- oped the techniques of psychoanalysis for treating mental disorders, which we discuss in our chapter on therapies. He popularized the use of psycho- logical principles for explaining everyday behavior, and his theories are just as likely to be discussed in your English literature course as they are in a psychology course.

Our enthusiasm for Freud is tempered by a number of valid concerns. As you read and hear about Freud throughout the remainder of this course, keep in mind that he did no real experimentation. His theories are based primarily on his own introspections along with those of his patients, who as primarily upper-class Viennese housewives were not typical of the general population. Freud’s theories do not lend themselves to experimentation, an essential requirement for any scientific theory, as we discuss further in our chapter on research methods. For example, how could you possibly design an experiment to demonstrate that dreaming about water indicates you have unconscious concerns about sex? Finally, although psychoanalysis is still used as a therapy technique, it is rarely conducted in the strict Freudian manner. Other techniques, discussed in our chapter on therapies, exceed psychoanalysis in effectiveness and popularity among therapists.

Humanistic Psychology By the 1960s, American psychology was primar- ily characterized by behaviorism on one side and Freud’s theories on the other. Structuralism had fallen into disfavor, and functionalism and Gestalt psychology were no longer distinct schools of thought. Just as other aspects of American culture began to feature rebelliousness against current ways of thinking, some psychologists began to push against the restrictions of behaviorism and psychoanalysis. Many of these disenchanted psycholo- gists had been trained in psychoanalysis, but were not seeing the results they desired. This dissatisfaction with prevailing views led these humanis- tic psychologists to propose new ways of thinking about the human mind.

Humanistic psychologists rejected the idea that people are innately uncivilized and must be taught to be good. Freud, James, and Skinner all believed that human behavior was on a continuum with animal behavior, which led to their assumption that humans naturally shared the aggressive impulses of animals. For Freud in particular, society had a civilizing func- tion on the otherwise selfish and aggressive human being. In contrast, the humanists extended the philosophy of Jean Jacques Rousseau and other 18th-century Romantic philosophers into a belief that people are innately good, are motivated to improve themselves, and only behave badly when corrupted by society.

Instead of focusing on what went wrong in people’s lives, humanist Abraham Maslow (1908–1970) asked interesting questions about what made a person “good.” Maslow introduced a major theory of motivation, which we describe in more detail in our chapter on motivation. According to Maslow, the pinnacle of motivation is the goal of self-actualization. The 1990s U.S. Army slogan, “Be all you can be,” captures much of the flavor of self-actualization. We will see Maslow’s emphasis on what is good about

In 1920, Francis Cecil Sumner (1895–1954) became the first African American to receive a PhD in psychology for his work on psychoanalysis. Sumner’s later work focused on religion and racism.

Abraham Maslow (1908–1970) contributed a theory of motivation to the growing humanism movement.

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HOW DID THE SCIENCE OF PSYCHOLOGY BEGIN? 25

Humanist therapists, like Carl Rogers (1902–1987), often rebelled against Freudian approaches to therapy. For example, Rogers (in the white shirt leading a group therapy session) referred to people as “clients” rather than “patients” as Freud did.

people, as opposed to Freud’s focus on what goes wrong with people, reemerge in the form of contemporary positive psychology.

Humanist therapists rebelled against Freudian approaches to treatment. One humanist therapist, Carl Rogers (1902–1987), developed a new approach to ther- apy, client-centered therapy. In this type of therapy, the people receiving treatment are referred to as clients rather than patients, reflecting their more equal stand- ing with the therapist and their more active role in the therapy process. Humanistic approaches to therapy have also influenced communication, group process, parent- ing, and politics. The emphasis on active listening and the use of “I hear what you’re saying” reflections have become nearly cliché in courses of leadership training and interpersonal communication. Advice to parents to provide “unconditional” love to their children is a direct application of humanist beliefs, which we discuss in more detail in our chapter on development. Finally, humanistic psychology continues to flavor our political and social domains. When issues such as capital punish- ment arise, the humanistic contention that there are no bad people, just bad societies, typically appears as part of the debate.

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY26

Summary 1.2 Pioneering Approaches to Psychology

Foundation of psychology Things to remember

Wilhelm Wundt (1832–1920)

Structuralism Behavior can be broken down into its components.

Max Wertheimer (1880–1943)

Gestalt psychology Breaking behavior into components loses meaning.

William James (1842–1910)

Functionalism Behavior is purposeful and contributes to survival.

Ivan Pavlov (1849–1936)

Behaviorism Experience is the primary source of behavior.

Ulric Neisser (1928– )

Cognitive revolution Private mental processing can be studied scientifically.

Sigmund Freud (1856–1939)

Freud’s psychodynamic theory Ideas about the unconscious mind, the role of experience in abnormal behavior, and new approaches to therapy laid a foundation for later study in personality and therapy.

Abraham Maslow (1908–1970)

Humanism People are naturally good and are motivated to improve.

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WHAT ARE PSYCHOLOGICAL PERSPECTIVES? 27

What Are Psychological Perspectives? Like William James, the behaviorists and Freudians tried to answer the “big questions” of psychology with one single approach. However, it is difficult to build a big theory (which we discuss in our research methods chapter) without a large body of experimental data, and psychology was still a young science. To fill this gap, some psychologists began to pursue an under- standing of behavior from more specific points of view, or perspectives. By specializing in only one part of the discipline, as opposed to trying to answer everything at once, these psychologists began to gain an in-depth understanding of the mind.

By the second half of the 20th century, the majority of psychologists were pursuing the perspective approach. Examining psychological phe- nomena from different perspectives does not imply disagreement, conflict, or a lack of awareness of alternate perspectives. In most cases, a psycholo- gist’s perspective simply means that he or she is examining behavior from that point of view. For example, watching a child learn a new vocabu- lary word will have very different meanings to the biological, devel- opmental, evolutionary, cognitive, social, or behavioral psychologist.

Reflecting the traditional divisions of the field, it is common for psychologists to refer to themselves as social psychologists, develop- mental psychologists, and so on, indicating their area of specialization and interest. Departments of psychology at universities often continue this organization, and students applying to graduate school in psy- chology might apply to one particular area of expertise, like choosing an undergraduate major. To illustrate the distinctions among some of the main perspectives, we will consider how each might approach the question of human memory, discussed in detail in a later chapter on memory, as this topic is especially important to students who wish to perform well on their exams.

Seven Perspectives of Psychology

Biological psychology, also referred to as behav- ioral neuroscience, focuses on the relationships between mind and behavior and their underlying biological processes, including genetics, biochemis-

try, anatomy, and physiology. In other words, biological psychologists are interested in the physical mechanisms associated with behavior. As we will see in our chapter on biological psychology, technological advances begin- ning in the 1970s, especially new methods for observing brain activity, initiated an explosion of knowledge about the connections between brain and behavior. Using these new technologies, biological psychologists have approached the question of storage and retrieval of memories in many dif- ferent ways, ranging from observing changes in communication between nerve cells in slugs to investigating the effects of stress hormones on the ability to form memories. The focus of this perspective is on the mecha- nisms used to store and retrieve memories, such as changes in the structure of nerve cells or in the biochemical environment of the nervous system.

biological psychology The psychological perspective that focuses on the relationships between mind, behavior, and their underlying biological processes, including genetics, biochemistry, anatomy, and physiology; also known as behavioral neuroscience.

The great question that has never been answered and which I have not been able to answer, despite my thirty years of research into the feminine soul, is “What does a woman want?” —Sigmund Freud

Biological psychologists explore the relationships between the mind, behavior, and their underlying biological processes, often using technology like functional magnetic resonance imaging (fMRI). Scott Grafton of the University of California, Santa Barbara is pointing out the features of the brain of one of your authors.

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Refleectctining g thhe traaditional divivisisions of thehe fifieldd, iit t is ccomommomon ffor hologigiststss to rrefeferer too tht emseelvves as socicialal ppsychcholologogisistts, deeveelolop-p- tall ppsysychologistss, and sso on, iindndicicatatingg ththeieir arrea of f spspeeciaialilizazatitionon nntereresst. Departtmmentnts of psychh lology at universities offten contiinue orgrgannizizata ion,n, aand students apapplying to graduate school in ppsy- ogy mmighht appply too one partiicucular arareaea of f exexpepertisise,e, likikee chchoooosisingng ndergrradaduuate mmajajor. To illustrtrate ththee didiststininctctioonns amoonng somomee oof

main perspectives, we will cononsisideder r hohow w eaeachch mmigighht aappprooaachh ththe e tion of human memory, discussed in detail in a later chapter on

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY28

Evolutionary psychologists are interested in how our modern behaviors were shaped by our species’ history.

evolutionary psychology The psychological perspective that investigates how physical structure and behavior have been shaped by their contributions to survival and reproduction.

cognitive psychology The psychological perspective that investigates information processing, thinking, reasoning, and problem solving.

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A closely related perspective, evolutionary psychology, attempts to answer the question of how our physical structure and behavior have been shaped by their contributions to our species’ survival. This perspec-

tive should sound familiar to you—it is a modern extension of William James’s functionalism, which we discussed previously. Earlier, we also saw evolutionary psychology at work in the shaping of our sensitivity to bitter tastes. The basic principle of evolutionary psychology is that our current behavior exists in its present form because it provided some advantage in survival and reproduction to our ancestors. An evolutionary psycholo- gist might be interested in the fact that we have a very good memory for faces, and particularly for faces of people who have cheated us in the past (Barclay & Lalumière, 2006). In the world of the hunter-gatherer, being cheated out of one’s fair share of the hunt was likely to lead to starvation for you and your fam- ily, and people who could not keep track of the cheaters were unlikely to survive and reproduce.

Cognitive psychology focuses on the process of thinking, or the processing of information. Because our ability to remem- ber plays an integral part in the processing of information, a

cognitive psychologist is likely to have a lot to say about the storage and retrieval of memories. A cognitive psychologist might ask why processing seems different when we are trying to remember names and dates while taking a history test compared to remembering how to ride a bicycle. What processes lead to the frustrating experience of “tip of the tongue,” in which you remember the first letter or a part of the word you’re trying to retrieve but not the whole thing? What strategies can we use to make our memo- ries more efficient? We address these and similar issues in our chapters on memory and cognition.

Social psychology is important to our understanding of many contemporary problems, including prejudice. In one experiment, some people describing what they heard from other participants about a drawing of a White man threatening a Black man with a razor switched the races of the two men (Allport & Postman, 1945). They now “remembered” hearing about a Black man threatening a White man. Given our judicial system’s dependence on eyewitness testimony, understanding these social tendencies provides important guidance.

A closely related perspective, evolutionary psychology, attemp answerr tthehe qqueeststioionn off hhow oour pphyhysisicacal struructc ure anand d bebehaavivioror been shhaped byy theheiri conontrtribibuttionsns tto our spececieiess’ sururvvival. Thiss pperers

tive sshoho luld sounund d fafamimilliaar tto yoyou——itit iis s a momodernrn extteensio WiW lliaiamm JaJameess’s funcnctionnalalisism,m, wwhihich wwee diiscscusussesedd prprevevioio Earlier, we also saw evolutionary psychology at work in shapping of our sensitivityy to o bbitter tastes. The bab sic princip evevololututioi nanarry psysychchoologogy y isi thahat ouour cuurrrenent t bebbbehavior exis ittss prp esenentt fof rmrm becauausee itt prprovoviddedd ssommee adadvantage in sur aandd rereprododucuctionon to o oour r anancceststoors. AAn n evevololutionary psych gist might be interested in the fact thahaat wwew have a very

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT ARE PSYCHOLOGICAL PERSPECTIVES? 29

Cognitive psychologists investigate the ways the human mind processes information.

Social psychologists explore the effects of the social environment on our individual behavior. In this example, the man in the middle is deciding whether or not to conform with the other two men in a simple judgment of line length.

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Social psychology describes the effects of the social environment, including culture, on the behavior of individuals. Social psychologists recognize that we each construct our own realities and that the social environment influences our thoughts, feelings, and behavior. Early psy- chologists were limited in their understanding of the mind by their exclu- sive focus on their own sociocultural contexts. More recently, social psychologists have emphasized the need to explore the influences of sociocultural context and biology on our behavior. Returning to our memory example, the social psychologist might ask how being in the presence of others influences the storage and retrieval of data. When we sit comfortably in our own homes, the answers to Who Wants to Be a Millionaire questions come quite easily. In front of millions of viewers, however, we might be lucky to remember our own names.

Developmental psychology explores the normal changes in behavior that occur across the lifespan. Using the developmental perspective, a psychologist might look at how memory func- tions in people of different ages. Three-month- old babies can retain the memory that kicking moves a mobile suspended above their crib for about a month without further practice (Rovee- Collier, 1997). However, most of us have difficulty recalling events that occurred before the age of 3 to 4 years or so. Teens and young adults are able to remember names much faster than are older adults (Bashore, Rid- derinkhof, & van der Molen, 1997). We explore these and other age-related changes in memory in our chapter on lifespan development.

Psychologists continue to be interested in what happens when nor- mal behavior breaks down. The clinical psychology perspective seeks to explain, define, and treat abnormal behaviors. More recently, clinical and counseling psychologists have expanded their perspective to include the

social psychology The psychological perspective that examines the effects of the social environment on the behavior of individuals.

culture The practices, values, and goals shared by groups of people.

developmental psychology The psychological perspective that examines the normal changes in behavior that occur across the lifespan.

clinical psychology The psychological perspective that seeks to explain, define, and treat abnormal behaviors.

information.es a mobilee susppended above their crib for t a month wwithoout further prpracactiticece (RoRoveveee- er, 11997)7). HHowevver, most ofof us havee ddiffiifficullty y rerecaalllinngg events thahat t rred beffore ththe agagee ofof 3 to 4 4 yey ars orr sso. TTeensns aandnd yyouungng adudultts arare e ttoo remmember nnaames mmuch fafaststerer tthah n n araree oldeder adulultsts (BaBashshororee, RRidid-

nknkhohof, & van der MMoolen, 1997). We explore these and other agge-related ges inn mmemoory y inin oour chapterer on lifesppan developpment. sychoologigists s coc nttiinue to bee iinterresesteted d inin wwhah tt hahappppenens whwhenn nnoro -- behaviior bbreaks down. The lcliniccalal ppsysychchololoogyy perssppecctiivee seseekks toto ain, define, and treat abnormmalal bbehehavavioiors. MoMoree rrecenently, ccliininicaall anndd seling psychologists have expanded their perspective to include the

F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY30

promotion of general well-being, which we describe in a later chapter on positive psychology. Many types of psychological disorders impact mem- ory. Freud believed that traumatizing experiences were more difficult to remember, a process he labeled repression (which will be discussed further in our chapters on memory and psychological disorders). In other cases, war veterans and others who have experienced trauma might be troubled by memories that are too good, producing intrusive flashback memories of disturbing events.

Finally, although much of psychology explores how the average person thinks, feels, or acts, some people are not average at all. Psychologists inter- ested in all varieties of behavior, not just the most typical types, pursue an individual differences perspective (see ● Figure 1.8). Recognizing individual differences is especially important to psychologists interested in variations in personality. Using our example of memory, we can see how individual differences in “need for cognition” can predict memory for verbal material (Cacioppo, Petty, Feinstein, & Jarvis, 1996). People who have a high need for cognition enjoy mental challenges, like solving difficult puzzles. As we’ll see in our chapter on social psychology, individuals who are high in need for cognition also respond differently to persuasive messages.

Developmental psychologists look at the behavior that is typical for people of certain ages, from infancy to old age.

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e have argued that restrict- ing our thinking about an aspect of mind to the

information provided by one perspec- tive can result in an incomplete pic- ture, but can this single-perspective approach actually lead us in the wrong direction?

The answer to that question is a resounding yes. Consider the fol- lowing example. You are a biological psychologist interested in the effects of amphetamine on aggression. You know from past experience that amphetamine makes individual rhe- sus monkeys quite a bit more aggres- sive than usual (we are unlikely to do this study with human beings,

due to ethical concerns discussed in our next chapter; Haber & Barchas, 1983). But you also know that rhesus monkeys are very social animals, so it doesn’t make much sense to study them in isolation. Much to your sur- prise, you find that amphetamine produces no effects at all on the aggressiveness of a colony of rhesus monkeys (Dawe, Davis, Lapworth, & McKetin, 2009).

Your single biological psychology perspective can help explain why the individual monkeys are more aggres- sive under the influence of amphet- amine, but it does not provide much help in explaining why you don’t see the same results when you study the

monkeys in a group. However, when you add the insights of social psychol- ogy to those of biological psychology, a clearer picture emerges. The social world of the rhesus monkey consists of a strong hierarchy, or pecking order, with each male monkey know- ing his position relative to all the others in the colony. Higher rank- ing monkeys engage in dominance behaviors, including vocalizations and threats, to remind the lower rank- ing monkeys about who is the boss. Lower ranking monkeys avoid aggres- sion and other signs of dominance by engaging in submissive behaviors designed to prevent aggression, such as imitation (Adams, 1982).

Can the Use of a Single Perspective Be Misleading?

Thinking Scientifically

individual differences An approach to psychology that investigates variations in behavior from one person to the next.

personality An individual’s characteristic way of thinking, feeling, and behaving.

e Use of a Single PPeerrssppeeccttiivvee sleading?

F O S T E R , C E D R I C 1 6 9 2 T S

WHAT ARE PSYCHOLOGICAL PERSPECTIVES? 31

Studying individual rhesus monkeys will provide useful information, but for these very social animals, incorporating a social perspective helps us understand them more fully.

When you take a monkey’s rank in the social hierarchy into account (adding the social perspective to the biological one), a clear picture of the results emerges. Amphetamine has different results on aggression that depend on the social status of the animal. Amphetamine increases domi- nance behavior by dominant monkeys and increases submissive behavior by submissive monkeys. If you just added up all the amphetamine effects for the group, the increases and decreases would cancel each other out, making it look like amphetamine had no effects at all. By adding the social perspective to the question, the discrepancy between the individual and group results can be explained easily. This example illus- trates that restricting ourselves to one perspective might cloud our under- standing.

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Individual Differences: The Geography of Personality. Where in the United States do you think the most outgoing, extroverted people live? Would you believe that North Dakota has more extroverts than California or New York? Psychologists studying individual differences found that the Midwest has the highest proportion of extroverted people in the country. Why would this be the case? Perhaps the need to develop tight social networks to survive the harsh climate in this part of the United States favored extroverts.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY32

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A New Connectivity: Integrating Psychology’s Seven Perspectives

Entering the 21st century and armed with in-depth research results compiled in the various perspectives, psychologists are returning to the more comprehen- sive view of the mind envisioned over 100 years ago by William James. Their questions and methods are more likely to blur the lines of the perspectives out- lined earlier, often with remarkable results.

Although the 20th-century perspective approach to psychology gener- ated detailed understanding of aspects of behavior and mental processes, it has become more apparent that single perspectives are insufficient for fully describing and explaining psychological phenomena. For example, if we want to understand the phenomenon of drug abuse, many perspectives can contribute to our understanding, but no one specialty offers a complete

explanation. Biological psychologists approach drug abuse by tracing pathways in the brain correlated with cravings, devel- opmental and social psychologists consider the family and peer influences, and so on. In each case, we learn something valu- able about drug abuse, but understanding the “whole” requires us to zoom out for a more comprehensive perspective (see ● Figure 1.9).

We don’t have a crystal ball that will allow us to foresee psy- chology’s future. However, we strongly believe that this future will be one of combining and integrating new and existing per- spectives. Many of these new ways of looking at the mind will take advantage of the revolution in techniques for studying the

Clinical psychologists seek to understand and treat psychological disorders.

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Using Multiple Perspectives Can Help Us Better Understand Complex Phenomena Like Drug Abuse. What accounts for the different patterns of use for these drugs? Single perspectives can only give us parts of the answer. Combining perspectives can give us the big picture.

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A Newww Connectivity: Integggrrratinggg Psychhhologggyyy’sss Sevennn Perspectives

EnEnteringng the 221s1stt cecentntuury anndd arrmemed d wwithh iin-n dd research results compiled in the various perspec psychologists arree returning to the more compre sisivee vvieieww ofof tthhe mminnd d enenvvisisiononeded ooovver 100 year byy WWilliamam Jammeses. TheTh irr qqueueststioions and method mmorere likkelely toto blulur ththe lilinenes ofof ttheh perspectives lined earlier often with remamaarkrkabable results

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT DOES IT MEAN TO BE A PSYCHOLOGIST? 33

Biological psychology

Cognitive psychology Social psychology

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Contemporary Psychology Integrates Seven Perspectives. Viewing the mind by zooming in using specialized perspectives has led to signi-ficant increases in our understanding, but 21st-century psychology is characterized by efforts to zoom out and integrate multiple perspectives.

F i g u r e 1 . 1 0

brain that began in the 1970s and continues. Already, today’s cognitive neu- roscientists investigate the brain as an information-processing system and search for the biological basis of topics such as attention, decision making, and memory. Social neuroscientists investigate the biological factors that vary along with people’s feelings and experience of social inclusion, rejec- tion, or loneliness. Behavioral neuroscientists pick up previous lines of research on learning, memory, motivation, and sleep and search for con- nections between these processes and our biology. Clinical and counsel- ing psychologists are more likely today to consider biological processes in their theories about the causes of psychological disorders. By merging our seven perspectives of mind, we stand a much better chance of tackling the remarkable problem of understanding the human mind (see ● Figure 1.10).

What Does It Mean to Be a Psychologist? In 2006–2007, more than 90,000 students in the United States received bachelor’s degrees in psychology (APS Observer, 2010). This amounts to approximately 6% of the 1.5 million bachelor’s degrees awarded that year. What are these students likely to be doing in the workforce?

Some students with undergraduate degrees in psychology prefer employment in fields that are directly related to psychology, such as work- ing in research facilities or rehabilitation centers for drug abuse or brain damage. Others are quite successful in a wide variety of “people-oriented” jobs, such as those found in management, sales, service, public affairs,

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY34

education, human resources, probation, and journalism. This diversity of career pathways reflects once again the “hub” nature of psychology to other fields.

Graduates with master’s degrees in psychology, usually requiring one to two years of additional study past the bachelor’s degree, can teach at the community college (2-year) level and obtain licensing as therapists in most states, as we discuss further in our chapter on therapies. Many mas- ter’s level psychologists are employed in health, industry, and education (American Psychological Association [APA], 2009). School psychologists typically work on elementary, middle school, or high school campuses. These psychologists participate in academic and career counseling as well as the identification and remediation of problems that interfere with stu- dent success.

Many people working in psychology have earned doctoral degrees, which usually take 2 to 5 years of study beyond the master’s level. As shown

lease don’t assume that we are trying to recruit

you to a career in psychol- ogy, but just in case you might con- sider the possibility of becoming a psychologist, you can take the follow- ing quiz to help you identify which type of psychology career might fit you best. Obviously, your campus

career counselors offer many addi- tional resources to help you make important choices about your career path, and we recommend that you take advantage of their expertise.

For each question, circle the answer that fits you best.

These questions can be used to divide students’ interests into

therapy, applied, and research tracks in psychology. Therapists, as we have described in this chapter, typically work with clients but might also teach. Examples of applied psychology include forensic psychology (applica- tion of psychology to the study of crime and the legal system) and sports

Which Psychology Careers Work for Me?

Experiencing Psychology

1. Do you enjoy working directly with people to help them overcome problems?

Yes No Sometimes

2. Do you enjoy solving theoretical problems? Yes No Sometimes

3. Do you enjoy classes that focus on experimental design? Yes No Sometimes

4. Are you good at mathematics and statistics? Yes No Somewhat

5. Do you enjoy working to solve practical, real-world problems?

Yes No Somewhat

6. Would you enjoy working with clients in a doctor’s office, hospital, or mental health clinic?

Yes No Somewhat

7. Is earning a high salary important to you? Yes No Somewhat

8. Are you able to deal with high-stress situations with people who may be psychologically or emotionally unstable?

Yes No Possibly

lease ddon’tt assusumem tthhat we are trying to recruit ou to a career in psychol-

st in case you might con-

caareer ccouounsnseelorss offoffeer mmaany adaddidi-- tiionnal resesouo rcess tto hehelp yoou mmaake immpoportrtanantt chchooiceess ababoout t yyourr ccareeeerr path, and we recommend that you

ttherapyy, aapppplilieded, and research tra inin psyycchoologogy.y. TTherapists, as we describedd ininn tthihis chapter, typical

PPssyychologyy CCareerss Work for Me?

F O S T E R , C E D R I C 1 6 9 2 T S

WHAT DOES IT MEAN TO BE A PSYCHOLOGIST? 35

Higher education 32%

Clinical 37%

School 8%

Business, government, and other 21% Not specified

in ● Figure 1.11, about 32% of new doctoral level psychologists do what your professor and the authors of your textbook do: teach and conduct research at colleges and universities. About 37% of new doctoral level psychologists work as therapists, either in private practice or in hospitals and clinics. Smaller numbers of new doctoral level psychologists find employment in business and government settings, elementary and secondary schools, and other related fields.

Psychologists entering doctoral programs traditionally identify with one of the major perspectives we discussed earlier, such as social, cognitive,

Where Psychologists Work. Within one year of graduation, individuals earning doctoral degrees between 2008 and 2009 found work in a variety of settings. The majority were employed in clinical and higher education settings, but opportunities for psychologists also exist in schools, businesses, government, and other settings where an understanding of human behavior is helpful. Source: Data from Michalski et al. (2011).

F i g u r e 1 . 1 1

psychology (working with athletes to optimize performance). Psychologists who teach and conduct research on college and university campuses have pursued the experimental track.

Use the following table to identify which of the tracks is most similar to your answers. Circle your answer for each question and see if you can find a pattern.

Question number Therapy Applied Experimental

1 Yes Sometimes No

2 Sometimes or No Sometimes or No Yes

3 Sometimes or No Sometimes or No Yes

4 Somewhat or No Somewhat or No Yes

5 Yes Yes Somewhat or No

6 Yes Somewhat No

7 Yes Yes Somewhat or No

8 Yes Possibly No

Answers

Sports psychologist Vietta Wilson uses biofeedback to help Canadian biathlete Graham Mater maximize his performance.

Forensic psychologists attempt to understand the criminal mind and to develop effective treatments for criminal behavior.

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sychologistts enntet ring doctoral programs traditionally identify with of thee mmajorr perspspectives we ddisiscucusssedd eeararlilier, susuchc ass ssociialal, cocogngnitivee,

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Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY36

or biological. The distribution of new doctoral graduates in psychology by perspective is shown in ● Figure 1.12. Choosing a graduate perspective is similar to choosing an undergraduate major. Although all psychology graduate students might take core courses in research methods and statis- tics, they typically pursue coursework and research in their particular area of specialization. However, training of psychologists in the 21st century is beginning to reflect the connections occurring in the field itself. Increas- ingly, students are being trained in combined specialties (e.g., cognitive neuroscience) as psychology becomes a more integrated field of study.

The most rigid distinction occurs between graduate students plan- ning to specialize in clinical or counseling psychology and those who do not. The clinical or counseling “major” includes extensive internships and supervised training prior to government-regulated licensure that usually add at least one year to students’ graduate studies. Do not assume that your psychology professors are all therapists. The likelihood is that they are not. It is also important to distinguish between therapists with doctoral degrees in psychology and psychiatrists, who are medical doctors. Cur- rently, the biggest difference between the two professions is that psychia- trists can prescribe medication, but psychologists usually cannot. In New Mexico and Louisiana, however, specially trained psychologists can legally prescribe medications, and this trend might spread to other states. In our chapter on therapies, we will provide more detail about the different types of therapists who treat adjustment problems and psychological disorders.

Clinical

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Psychological Perspectives. Students receiving doctoral degrees in 2008–2009 might have identified with one of these major perspectives, but increasingly, doctoral students are choosing to train in multiple or integrated perspectives, such as cognitive neuroscience. Source: Data from Michalski et al.

(2011).

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prescribe medications, and this trend might spread to other states. In chapter r onon ttheh raapipieses, wee wwill prooviddee momorere detaiaill about t ththee didiffereentnt tt of theeraapists whho trtreae t adadjujusts mementt pproblems anand d ppsycchohologig cal ddisosordrd

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WHAT DOES IT MEAN TO BE A PSYCHOLOGIST? 37

Summary 1.3 Seven Psychological Perspectives

Perspective Things to remember Biological psychology Investigates the connections between

the mind, behavior, and biological processes

Evolutionary psychology Asks how our evolutionary past continues to shape our behavior

Cognitive psychology Investigates mental processes including thinking, problem solving, and information processing

Social psychology Asks how our behavior is affected by the presence of others

Developmental psychology Investigates the normal changes in behavior that occur across the lifespan

Clinical psychology Explains, defines, and treats psychological disorders and promotes general well-being

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Individual perspective and personality

Recognizes that behavior varies around averages and that individual differences often interact with environments.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY38

Summary 1.3 (continued) What Do Psychologists Do?

Typical academic degree Possible areas of employment Bachelor’s degree Rehabilitation, research assistance, management, sales,

service, public affairs, education, human resources, probation, journalism

Master’s degree Community college teaching, marriage and family counseling, health, education

Doctor of Philosophy (PhD) University teaching and research, therapy, business, government, education

Medical doctor (MD)* Psychiatry

*Medical doctors who practice psychiatry are not really “psychologists,” as implied by the title of the table, but we think it’s important for you to know where they fit in.

Interpersonal Relationships From the Psychological Perspective We gave quite a lot of thought to how we might help you, the students reading our book, to see psychology more as an interconnected discipline than as a collection of separate perspectives. The introductory psychology course provides a unique opportunity to see all the perspectives at one time, in contrast to upper division courses that typically focus on one spe- cialty area at a time (personality, social, cognitive, and so on).

One way to connect the dots is to take a single problem and see how the different perspectives represented in the subsequent chapters would address it. We used a mini version of this approach in this chapter when we discussed memory from the vantage point of each perspective. In each chapter, this feature will have more of a perspective flavor, but by the end of the textbook, you will have seen everybody weigh in with different per- spectives to give you the whole picture. Because it is most helpful to know something about the perspectives before seeing how they apply, we are saving this feature for the end of each chapter. Ideally, seeing the chapter material in action will make it more memorable for you.

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F O S T E R , C E D R I C 1 6 9 2 T S

INTERPERSONAL RELATIONSHIPS FROM THE PSYCHOLOGICAL PERSPECTIVE 39

The single problem we have chosen to consider this way is one that we know to be on the minds of many of our students: relationships. We are a social species, and the quality of our relationships has a huge impact on our physical and psychological well-being (Cacioppo & Hawkley, 2009). We will see how each of the major perspectives view the question of quality relationships and how the perspectives work together to give us the best understanding possible of this important aspect of life.

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By three methods we may learn wisdom: First, by reflection, which is noblest; second, by imitation, which is easiest; and third by experience, which is the bitterest. —Confucius

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter Reflections

Chapter 1 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY

This chapter began with a question about why we are so much more sensitive to bitter tastes than to sweet tastes. Initially, this question might have seemed straightforward, best answered by a psychologist who special- izes in sensation and perception. We hope that after reading this chapter, you now realize that yes, the specialist has a great deal to say about taste, but we more fully understand psychological questions when we integrate the explanations of specialists working in multiple perspectives. Just as the Gestalt psychologists that you read about in this chapter believed that perceptions were different than the sum of individual sensa- tions, we believe that our understanding of psychological phenomena ben- efits from the integration of the contributions of individual specialties. In the case of the bitter tastes, the sensation and perception specialist might emphasize the physical qualities of the taste stimulus, the taste receptors, and the pathways taken by taste information to the brain. Although this is essential and useful information, we gain even more understanding by integrating the specialist’s information with input from additional perspec- tives. The evolutionary perspective highlights the benefits of sensitivity to bitter tastes for avoiding poisons, which of course enhances survival. The

developmental perspective reminds us that children are more sensi- tive to taste than adults, which is probably why the bitter

broccoli elicits a strong response from the little boy in the photograph at the beginning of the chapter.

Our social connectivity and culture also play important roles, as we eat differently in the presence of others and form likes and dislikes depending on our exposure to certain flavors. In the remaining chapters, we will continue to emphasize benefits of zooming

out periodically to view the whole of psycho- logical phenomena, not just the separate parts

contributed by single perspectives. <

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F O S T E R , C E D R I C 1 6 9 2 T S

CHAPTER REFLECTIONS

KEY TERMS The Language of Psychological Science Be sure you can define these terms and use them correctly. behaviorism, p. 18 biological psychology, p. 27 clinical psychology, p. 29 cognitive psychology, p. 28 culture, p. 29 developmental psychology, p. 29 evolutionary psychology, p. 28

functionalism, p. 15 Gestalt psychology, p. 15 humanistic psychology, p. 24 individual differences, p. 30 introspection, p. 5 mind, p. 5 personality, p. 30

philosophy, p. 6 physical science, p. 6 psychology, p. 5 social psychology, p. 29 structuralism, p. 14

MEDIA RESOURCES Log in to CengageBrain to access the resources your instructor requires. For this book, you can access:

Psychology CourseMate brings course concepts to life with interactive learning, study, and exam preparation tools that support the printed textbook. A textbook- specific website, Psychology CourseMate includes an integrated interactive eBook and other interactive learning tools including quizzes, flashcards, videos, and more.

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required by your professor. 3. When finished, click “Grade It Now” to see which areas

you have mastered, which areas need more work, and detailed explanations of every answer.

ith interactivve learnning, study, and exam preparation that support tthe prrinted textbook. AA ttexextbt oookk- fic wewebsbsitite,e, Psyycholoogy CourseMaMatte inclludees an e ratedd iintntereractiveve eeBoBookk aand otheer iinteractivee leaearnrning inclclududing quizzes, flflashcarards, videdeosos, , annd d mmorre.

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F O S T E R , C E D R I C 1 6 9 2 T S

Scientific methods, including brain imaging, have allowed researchers to pinpoint structural and functional differences between the brains of fluent speakers and people who stutter.

F O S T E R , C E D R I C 1 6 9 2 T S

The Measure of Mind

Methods of Psychology

1 Describe the criteria that distinguish scientific observation and reasoning from casual, everyday thinking.

2 Articulate how science uses testable and falsifiable hypotheses, data collection, peer review, and replication to evaluate theories explaining psychological phenomena.

3 Explain the main goal of descriptive research methods and the ways in which case studies, naturalistic observations, and surveys approach this goal.

4 Differentiate the key features, strengths, and limitations of correlational and experimental methods, and apply this distinction in designing a new study or interpreting the results of a study.

5 Compare and contrast cross-sectional versus longitudinal methods for studying change in psychological processes over time.

6 Define reliability and validity, and evaluate a specific operational measure of a variable with respect to these criteria.

7 Differentiate the kind of information conveyed by descriptive versus inferential statistics in describing scientific data, and interpret the meaning of specific statistics (e.g., mean,

correlation coefficient).

8 Evaluate specific psychology studies in terms of the ethical guidelines for using human and animal participants in research.

Learning Objectives

The Oscar-winning film, The King’s Speech, chronicled the struggles of Great Britain’s King George VI as he attempts to overcome his stuttering. Stuttering involves disruptions in normal speech production, such as repeating the starting letter of a word (b-b-b-bird), holding a vowel sound for a long time (ah ah ah), or having difficulty initiating any speech at all. About 5%

of the population experience stuttering (Månsson, 2000), with males 2 to 5 times more likely to stutter than females

(Craig & Tran, 2005).

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4 Differentiate the key features, strengths, and limitations of correlational and expe meth dods, and apply this distinction in designininng a new study or interpreting the r studyy.

5 Comppare annd cocontntraastt ccror sss-sseectionnaal veerssuss loonngiituddinnal mmetethohods for studying ch psychoholologigicacall prprococesssesess ovover ttiime.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 2 44

Stuttering has been described since the days of the ancient Greeks and occurs across all cultures and ethnicities. Many interesting myths exist regarding its causes and remedies (Kuster, 2005). South African tradi- tions suggest that stuttering results from leaving a baby out in the rain or tickling it too much. A Chinese folk remedy for stuttering was to hit the person in the face when the weather was cloudy. In Iceland, a pregnant woman who drank from a cracked cup was likely to produce a child who stuttered.

Of course, many of us might ask, “How could anybody believe these things?” But at the end of the day, how do we know these are merely myths and not facts? How can we be so sure? Instead of dismissing these efforts to explain and predict, think about what might have happened to

lead people to these particular conclusions. What is missing from these conclusions is a system for reaching logical, objec- tive results. Science provides us with this system. What does science have to say about stuttering today? Based on the careful evaluation of stuttering using the methods outlined in this chapter, scientists have concluded that there are multiple causes for stuttering (Kang et al., 2010). Many cases seem to have a basis in genetics, which we discuss in the next chapter. Using scans of brain activity has allowed scientists to zoom in on brain structures and functions that appear to differ between stutterers and fluent speakers, with stutterers showing more activation of the right hemisphere during speech (Gor- don, 2002). As we mentioned in our previous chapter, some of the most thorough explanations combine multiple psycho- logical perspectives (Ward, 2006). A complete explanation of stuttering zooms back out to combine a predisposition for the

problem, through genetics and biology, with developmental, emotional, and social factors, like feeling embarrassed or anxious about speaking in front of peers.

Although there is no “cure” for stuttering, carefully tested scientific explanations combining input from various perspectives are leading to more effective treatments. In this chapter, you will learn how science pro- vides a system that allows us to construct increasingly realistic models of the world around us.

What Is Science? Throughout our history, we human beings have been motivated to under- stand, predict, and control the world around us. To meet these goals, we need methods for gaining knowledge.

We often take contemporary scientific knowledge for granted, but our ancestors did not enjoy the benefits of science while trying to explain their world. Very early in history, people attempted to understand natural phenomena by applying human characteristics to nature (Cornford, 1957). Skies could look angry or a lake could be calm. Other explanations involved

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Science is a special way of learning about the world through systematic observation and experimentation. These children are learning about the science of the mind during the Dana Foundation’s Brain Awareness Week.

chapter. Using scans of brain activity has allowed scientists zozoomom iinn onon braraini strruuctureres s anandd funcctitions thhatat aappppearr toto dd betweeeenn sts utttererersrs aannd flfluuent spep akkererss, wwithh sstuttererss sshohoww more aactivatioonn ofof tthehe rigighht hhememisphpherere dudurir nng spep eechh (G(Go dodon, 2200002)2). AsAs we mementioonened d inin oourur preeviviouss chchapaptter, ssomomee of the most thorough explanations combine multiple psych logig cal perspep ctives (Ward, 202006). A complp ete e explanation sttututteteriringg zoooomms bbacack k ouout t too ccomombibinene aa ppreredidiiisspsposition for

problem,m thrrououghgh ggenenete iicss aand bbiolloggyy, wwiithh deevvelolopmpmental, emotiona and socicialal ffactotorsrs, lilikeke ffeeelilinng eemmbararrassssedd or ananxixiououss aba out speaking front of peers

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT IS SCIENCE? 45

Science has provided us with explanations for many natural phenomena, like thunder and lightning, that were probably quite frightening for our ancestors.

Science strives to be objective, which means to make judgments that are free from personal emotion or bias. In contrast, people’s subjectivity emerged in a classic experiment by Allport and Postman (1945). Some participants remembered hearing that this picture illustrated a Black man threatening another person rather than the objective fact—a White person is doing the threatening.

science A method for learning about reality through systematic observation and experimentation.

objectivity The practice of basing conclusions on facts without influence of personal emotion and bias.

spirits, which were found in humans and all other objects. Earthquakes and illness were viewed as the actions of spirits, and people attempted to influ- ence these spirits through magical rituals.

People often form strong beliefs about their world based on faith, which literally means “trust.” Faith is belief that does not depend on logical proof or evidence. We might accept a friend’s excuse for being late based on our faith in his or her honesty, without knowing for certain whether our friend is really telling the truth. Science, in contrast to faith, absolutely requires proof and evidence. Our word science comes from the Latin sci- entia, which means “knowledge.” Science doesn’t refer to just any type of knowledge but, rather, to a special way of learning about reality through systematic observation and experimentation. The methods we describe in this chapter are designed to supply that evidence.

The Scientific Mind-set

Not all observations are scientific. How does sci- ence differ from everyday observations, like the belief that “opposites attract”? As you will learn in

our chapter on social psychology, “opposites” do not, in fact, find each other very attractive.

First, science relies on objectivity rather than subjectivity. Objectivity means that conclusions are based on facts, without influence from per- sonal emotions or biases. In contrast, subjectivity means that conclusions reflect personal points of view. In the previous chapter, you read about what happened when research participants described what they had heard about photos from memory. Some participants switched the race of a man threatening another person from White (which was the objective fact in the photo) to Black (possibly to fit a biased subjective worldview).

Scientists strive to be objective, but any observation by a human being is, by definition, subjective. Recognizing when you are being subjective can be difficult, so scientists cannot rely on their own introspections to

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atteneniing g another peperson from White (which was the objectiveve fact in hoto)o) to Blaack (p(posossibly to fifit a biasseded subbjejectc ive e woworlrldvdvieiew)w).. cientiists sstrivivee toto bbe objectivvee, butut aanyny obsbserervvattioon bby a huhumaman bebeiningg y definition, subjective. Recocogngnizizining g whwhenen youou aare bbeingng ssuubjjecctivvee be difficult, so scientists cannot relly on thheir own introspections to

F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY46

maintain objectivity. Most of us have had the experience of wit- nessing an accident in the presence of other people. It can be astonishing to hear the different accounts of what just happened. Didn’t we all see the same thing? Of course, we like to believe our view of the events is the accurate one. As we discuss in later chapters on memory and cognition, objective facts can be altered easily when processed subjectively by individuals. The scientific methods described in this chapter promote objectivity and help prevent biased, subjective observations from distorting a scien- tist’s work.

We have all had the experience of witnessing an event with other people only to discover that everyone seems to have a different memory of what happened.©

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Psychology as a Hub Science

Testing the Effects of Food Additives on Children’s Behavior

ow many times have you heard a parent complain

about a child’s out-of- control behavior and blame it on too much sugar? How would a scientist know if sugar or any other food ingre- dient affected children’s behavior? Scientific discoveries in this area could

benefit the fields of nutrition, health, medicine, and child development.

Psychologists have employed the objective, scientific methods needed to provide guidance to both parents and the food industry on this type of topic. So how can scientists objec- tively test the idea that kids may go “out-of-control” after eating too much sugar? What tools can a scientist use? The “gold standard” for demonstrating the objective effects of any substance, whether a food additive, medication, or recreational drug, is the double- blind procedure. This procedure requires a placebo, an inactive sub- stance that cannot be distinguished from a real, active substance.

The first “blind” aspect of this pro- cedure is the inability of participants to know whether they have taken a real substance or a placebo. This feature controls for any effects of the partici-

pants’ expectations. When we drink coffee, for example, we expect to feel more alert, or when we take an aspirin, we expect our headache to disappear, so we may “feel” better long before the substance has had time to actually pro- duce any effects. Not letting the sub- ject know whether he or she received the real substance or the placebo helps offset these misleading effects.

The second “blind” is achieved when the researcher does not know if a participant has been given a real substance or placebo until the experi- ment is over. This aspect ensures that the researcher’s own expectations do not tilt or bias his or her observations. If scientists expect participants to act more alert after drinking coffee, for example, this bias could be reflected in their observations and conclusions.

Returning to our question of food additives, what do double-blind,

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT IS SCIENCE? 47

The second important difference between science and everyday obser- vations is the use of systematic observation as opposed to hit-or-miss observation. By “hit or miss,” we mean making conclusions based only on whatever is happening around us. If we want to make conclusions about the “human mind,” we cannot restrict our observations to our immediate circle of acquaintances, friends and loved ones. Your observations of the people you see frequently are probably quite good. It’s just that the people we know represent a small slice of the greater population. We might be surprised to learn that our favorite candidate lost an election, because “everyone we know” voted for him or her.

Based on observations of their surroundings, college students often believe that drinking alcohol, and even binge drinking (five drinks on one occasion for men, four for women), is a nearly universal behavior for any- one over the age of 18 or so. We can see why a college student might believe this after making hit-or-miss observations. According to the U.S. Depart- ment of Justice, 51% of 18- to 21-year-olds reported at least one drinking occasion in the last 30 days, and 37% of this age group reported at least one binge episode during that period (U.S. Department of Justice, 2002). However, this same study showed that 46% of American adults 21 and older do not drink alcohol at all, and another 26% have one drink or less per

placebo-controlled studies have to say about their effects on child behavior? In one careful study, young children were given drinks that either had no additives (placebo) or a com- bination of colorings and preserva- tives used frequently in packaged foods (McCann et al., 2007). Because it was a double-blind study, the chil- dren, of course, did not know which drink they had received, nor did the researchers responsible for observ- ing the children. The outcome of this study showed that general measures of hyperactivity, or unusually large amounts of movement, were higher in the group that had consumed the additives than in the group consum- ing the placebo. This finding has implications for attention deficit hyperactivity disorder (ADHD), which we discuss in a later chapter on psychological disorders. The ability of these common food additives to make normal children more hyperac- tive is cause for concern and worthy of further study (see ● Figure 2.1).

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Double-blind placebo-controlled studies have provided insight into the relationship between common food additives in fruit drinks and hyperactivity in children.

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F i g u r e 2 . 1

Measure what is measurable, and make measurable what is not so. —Galileo Galilei

double-blind procedure A research design that controls for placebo effects in which neither the participant nor the experimenter observing the participant knows whether the participant was given an active substance or treatment or a placebo.

placebo An inactive substance or treatment that cannot be distinguished from a real, active substance or treatment.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY48

week. An additional 5% drink more than one drink per week, but never four or five on one occasion. As shown in ● Figure 2.2, binge drink- ers comprise only about 23% of the adult population (compared to the 37% percent of 18- to 21-year-olds), and only 7% of adults over 21 binge five or more times per month. These numbers, while significant (binge drinkers consume a whopping 76% of the alcohol sold in the United States), hardly support a conclusion that “everybody’s doing it.”

Finally, science relies on observ- able, repeatable evidence, whereas everyday observation often ignores

evidence, especially when it runs counter to strongly held beliefs. Many people are quite convinced that women talk more than men. We’re not certain where that idea came from, and it does not appear to be true. One group of researchers recorded students’ talking throughout the day and concluded that “the widespread and highly publicized stereotype about female talkativeness is unfounded” (Mehl, Vazire, Ramírez-Esparza, Slatcher, & Pennebaker, 2007, p. 82). Other studies, in fact, make the argu- ment that in the majority of circumstances, men actually talk more than women (James & Drakich, 1993; Leaper & Ayres, 2007).

Scientific knowledge is both stable and changing. It is a work in prog- ress, not a finished product. The fact that we may learn something new tomorrow should not convince you that today’s knowledge is flawed. Most change occurs very slowly on the “cutting edges” of science, not quickly or at the main core of its knowledge base. Unlike with many other fields, we expect science to improve over time. An important feature of scientific literacy is to learn to be comfortable with the idea that scientific knowledge is always open to improvement and will never be considered absolutely cer- tain (American Association for the Advancement of Science, 2009).

The Importance of Critical Thinking

Critical thinking, or the ability to think clearly, rationally, and independently, is one of the founda- tions of scientific reasoning. The skilled critical thinker can follow logical arguments, identify mis-

takes in reasoning, prioritize ideas according to their importance, and apply logic to personal attitudes, beliefs, and values.

Critical thinking is not built in but, rather, is a skill people need to learn. You can begin by using five critical thinking questions to evaluate new information you come across in your everyday life, starting with what you read in this textbook (Bernstein, 2011):

1. What am I being asked to believe or accept? 2. What evidence supports this position?

76%

Although binge drinkers make up only 23% of the adult population, they consume an astonishing 76% of all alcohol sold in the United States.

Nondrinkers 46%

Nonbingers 31%

Infrequent bingers 16%

Frequent bingers 7%Scientific Observations Are

Systematic, Not Hit-or-miss. Science provides ways to make systematic observations. Judgments we make based on the people we know might not apply to larger groups of people. Binge drinking is more common among 18- to 21-year-olds (37% report at least one binge in the last 30 days) compared to adults over 21 (23%). Among adults in general, 46% do not drink at all and another 26% report having one drink per week or less. Source: Data from U.S. Department of Justice (2002).

F i g u r e 2 . 2

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critical thinking The ability to think clearly, rationally, and independently.

One group of researchers recorded students talking throughout the and cooncncluluded d ththatat “thhee widedespreeadad aandn higighlh y puublblicicizizede ssteerereoo about t fefemale tallkakatitivev neessss iiss unfoununded” ((Mehlhl, VVazirere, Ramírezz-EsEspp SlS atchherr, & Pennneebaker, 2200707,, pp. 82)2). Ottheherr sttududieies,s, in faact, mamakee tthe a mment tthahatt inin thee mmajajoritityy of ccirircumsmstatancnceses,, mmen acactualallyly ttalalkk momorere women (James & Drakich, 1993; Leaper & Ayres, 2007).

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WHAT IS SCIENCE? 49

3. Are there other ways this evidence could be interpreted? 4. What other evidence would I need to evaluate these alternatives? 5. What are the most reasonable conclusions? It is also helpful to recognize the signs that you are not thinking criti-

cally (Lau & Chan, 2009): Instead of figuring out the answer to a problem yourself, you prefer just being given the answer. You prefer to use “gut feelings” about decisions instead of using reason to choose a solution. You do not review your mistakes or change your mind if evidence contradicts your original position. You resent criticism of your ideas.

Critical thinking is not only essential to good science, but it provides the underpinning of a free society as well. Our abilities to think clearly, rationally, and independently give us the confidence to question the actions of people in authority instead of engaging in blind obedience. We hope you will continue to practice good critical thinking skills long after you com- plete this textbook.

The Scientific Enterprise

Learning scientific facts is not the same as under- standing how science works. Science, including psy- chological science, is more than a collection of

facts—it is a process.

Scientific Theories Science seeks to develop theories, which are sets of facts and relationships between facts that can be used to explain and pre- dict phenomena (Cacioppo, Semin, & Berntson, 2004). In other words, scientists construct the best possible models of reality based on the facts known to date. Unfortunately, the English language can be the source of considerable confusion regarding the nature of scientific theories. In addi- tion to its use in science, the word theory can be used in nonscientific ways to describe a guess, such as “I have a theory about why my professor seems

theory A set of facts and relationships between facts that can explain and predict related phenomena.

Scientific research results do not support the common stereotype that women talk more than men.

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY50

unusually cheerful this morning,” or a hypothetical situation, as in “that’s the theory, but it may not work in practice.” Confusion over the multiple meanings of the word theory have led people mistakenly to view truly sci- entific theories, like the theory of evolution, as nothing more than casual guesses or hunches rather than the thoroughly investigated and massively supported principles that they are.

et’s see how we might apply the five steps of critical thinking to exam-

ine journalists’ interpretation of the results of a recent survey. Major news outlets, including the New York Times, The Wall Street Journal, USA Today, and the Associated Press, featured stories about one of the interesting outcomes of the U.S. Census Bureau’s 2009 American Community Survey. For the first time in recorded U.S. history, fewer 25- to 34-year-olds are married than have never been mar- ried. Journalists were quick to blame the economy for this change. Among the headlines were “Saying No to ‘I Do’ With the Economy in Mind” and “Recession Spurs Young in US to Forgo or Delay Marriage.” How do we know whether a bad economy really influences marriage rates?

1. What am I being asked to believe or accept? I’m being asked to believe that there is a direct link between the U.S. recession and young adults’ decisions to marry.

2. What evidence supports this position? The American Community Survey, conducted by the Census Bureau, is an “ongoing survey that provides data every year. . . . Information from the survey generates data that help determine how more than $400 billion in federal and state funds are distributed each year” (U.S. Census Bureau, 2011). The survey includes questions about age, sex, race, family and relationships, income, health insurance, education, veteran status, disabilities, work transportation, and cost of living. Over 2 million respondents representing all geographical locations in the United States participated in the survey by mail, phone, or personal interview. To characterize the economy as a recession, the USA Today article cited additional facts from the Census Bureau survey, including a nearly 3% drop in median family income from 2008 to 2009 and the highest number of people living in poverty recorded in the last 51 years (El

Nasser, Overberg, & Thomassie, 2010). As we discuss later in the chapter, the median divides the population in half, so the median family income is the point where half of American families have incomes above that point and the other half have incomes below (see ● Figure 2.3).

3. Are there other ways this evidence could be interpreted? Economists agree that the United States was experiencing a severe recession when the survey data were being collected, but there are many reasons why people choose to get married. Some, but not all, of these reasons relate to finances. As you will learn in this chapter, these sorts of comparisons (between the population’s finances and its marriage rates) are known as correlations, and correlations do not give us the information we need to say “the recession caused a drop in marriage rates.” All we can say is that marriage rates went down at the same time financial indicators went down.

Using the Five Steps of Critical Thinking to Evaluate Survey Data

Thinking Scientifically

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WHAT IS SCIENCE? 51

What Do These Data Really Mean? News headlines were quick to associate a recent drop in marriage rates among young adults with the tough economy. Do the data really support that conclusion? Sources: Data from Mather and Lavery (2010); Pisani (2009).

F i g u r e 2 . 3

4. What other evidence would I need to evaluate these alternatives? Historical data on marriage rates would be helpful. Was the observed drop unique to 2008–2009? Did similar drops occur in previous recessions?

5. What are the most reasonable conclusions? Economist Justin Wolfers looked at marriage rates over time, including during periods of economic recession. Based on this analysis, he concluded that the trend for Americans to marry at later ages appears to have had more of an impact than the economy on the observed drop in marriage rates. The median age at first marriage for men has risen from 23 in 1970 to 28 today, and for women from 21 in 1970 to 26 today (Wolfers, 2010). Because of this trend, we would expect to see many fewer married 25- to 34-year- olds today than in 1970, and some of these young adults may eventually marry at later ages.

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The best scientific theories not only explain and organize known facts, but they also generate new predictions (see ● Figure 2.4). The word predic- tion comes from the Latin words for “saying before.” A scientific predic- tion is much more than a guess or hunch. It is usually stated in a rigorous, mathematical form that allows the scientist to say that under a certain

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY52

A contemporary theory of emotion correctly predicted the circumstances for when we might experience mixed emotions of happiness and sadness. Graduation from college is an important accomplishment, but we might feel sad about leaving our friends.

hypothesis A proposed explanation for a situation, usually taking the form “if A happens then B will be the result.”

falsifiable A characteristic of a scientific hypothesis meaning that situations in which the hypothesis might be false can be imagined.

testable A feature of a hypothesis that means it can be evaluated using known scientific methods.

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set of circumstances, the following outcomes are likely to occur (if A, then B). In some cases, a theory’s predictions can be quite

surprising. For example, you might believe that it’s impossible to be happy and sad at the same time. However, one model of emotion,

discussed in a later chapter, predicted that it is quite possible to feel happy and sad at the same time (Cacioppo, Berntson, Norris, & Gollan, 2011). This prediction was confirmed by research showing that first-year college students reported feeling either happy or sad, but not both, on a normal day of school, but experienced both emotions simultaneously on the day they moved out of campus housing to go home for the summer.

Before attempting to generate your own scientific questions, it pays to become very familiar with relevant theories and previ- ous discoveries. As Sir Isaac Newton noted, scholars stand on the shoulders of giants—we build on the work of those who came before us. New lines of research can also originate in observa- tion. Scientists are observers not just in the laboratory but in everyday life. Scientific progress often takes a giant leap forward when a gifted observer recognizes a deeper meaningfulness in an everyday occurrence, as when Sir Isaac Newton observed a fall- ing apple and considered its implications for a law of gravity. As we discovered in the previous chapter, Ivan Pavlov realized that when his dogs learned to salivate to signals predicting the arrival of food, something much more significant than slobbering dogs was happening. The learning he observed explains why we get butterflies in our stomach before a performance and avoid foods that we think made us ill.

Generating Good Hypotheses: Falsifiability and Testability Based on your understanding of past work and theoretical foundations in your area of interest, coupled with your own observations, you can now generate a hypothesis, which is a type of inference, or, in other words, an educated guess, based on prior evidence and logical possibilities. Scientific hypoth- eses must be both falsifiable and testable. Falsifiable does not mean “false.” Instead, falsifiable means that you can imagine situations that demon- strate your hypothesis to be false. For example, a hypothesis claiming that all planets outside our solar system are uninhabited is falsifiable, because finding an inhabited planet outside our solar system would show that your hypothesis was wrong. Hypotheses can be falsifiable but not necessarily testable, which means you can evaluate the hypothesis using known sci- entific methods. In our example of inhabited planets, we do not have the necessary technology to survey all the planets outside our solar system to determine whether an inhabited one exists. Our hypothesis is falsifiable but not currently testable.

Scientists can never “prove” that their hypotheses are true, because some future experiment, possibly using new technology not currently available, might show the hypothesis to be false after all. All we can do is show when a hypothesis is false. A false hypothesis must always be modi- fied or discarded. As we explore the universe, continued failure to find an inhabited planet does not mean our hypothesis is true. The only outcome

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WHAT IS SCIENCE? 53

of our search that would affect our hypothesis is the discovery of the very first inhabited planet, which would show that our hypothesis is wrong.

Evaluating Hypotheses Once you have a falsifiable and test- able hypothesis, you are now ready to collect the data necessary to evaluate it. The existing scientific literature in your area of interest provides considerable guidance regarding your choice of materials, types of data to be collected, and methods for inter- preting your data. To explore the many techniques available to psychologists, we will use an ongoing question about whether playing violent video games increases physical aggression. We could benefit from many other studies that specify features of violent video games, mea- sures of physical aggression, and statistical procedures for evaluating this type of question. You do not have to rein- vent the wheel. In fact, your results will be given greater consideration if you use methods that are well established and familiar in your area of research. Once we collect our data, our theories help us evaluate the importance and implica- tions of our observations.

Science is a vastly collaborative enter- prise. Not only do we “stand on the shoul- ders of giants” because we benefit from the work that has been done previously, but we depend on many others in the scientific community to help us improve our work and avoid mistakes. Normally this evaluation is done by submitting research to conferences or for publica- tion. During this process, research undergoes peer review, in which it is scrutinized by other scientists who are experts in your area. Only if other experts conclude that your research is important, accurate, and explained thoroughly will it be added to the existing body of scientific knowledge. To demonstrate the importance of this peer review, contrast this process to what happens when a person simply decides to transmit a tweet or launch a personal website. The author is solely responsible for the content, and there are no checks at all on the accuracy of that content.

During peer review, research that fits with our existing knowledge is typically accepted more rapidly than work that is less consistent with previous reports. Unconventional findings often undergo replication, which means that other scientists independently attempt to reproduce the results of the study in question. If the data are replicated, they will be accepted quickly. If other scientists are unable to replicate the data, their extra effort will have prevented inaccurate results from cluttering the sci- entific literature. Although this process might slow down the publication of some innovative research, the result—more accuracy—is well worth the effort.

A whopping 80% of Americans believe in a hypothesis suggesting that the government covers up all evidence of extraterrestrial life (CNN, 1997). Is this a falsifiable hypothesis? If you can even imagine the government suddenly placing an alien spaceship on display at the Smithsonian, the hypothesis can be shown to be falsifiable.

Hypotheses must be falsifiable, which means that we can imagine situations that show our hypothesis is false. A hypothesis stating that all planets outside our solar system are uninhabited meets this test, because finding life on another planet would show that the hypothesis was wrong. A NASA scientist, Dr. Richard Hoover, made a controversial claim that alien life similar to this microbe was recovered from a meteorite.

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY54

Summary 2.1 Steps to Critical Thinking

Questions for good critical thinking

Questions for detecting poor critical thinking (all answers should be no)

What am I being asked to believe or accept? Am I accepting another person’s conclusion without working out the problem myself?

What evidence supports this position? Am I using “gut feelings” instead of reason?

Are there other ways this evidence could be interpreted? Am I forgetting to review my conclusions to check for mistakes?

What other evidence would I need to evaluate these alternatives?

Am I oversensitive to criticism about my conclusions?

What are the most reasonable conclusions? Am I unwilling to consider alternative explanations?

How Do Psychologists Conduct Research? Psychologists use a variety of research methods, including descriptive, cor- relational, and experimental methods. Descriptive methods, including sur- veys, case studies, and observations, provide a good starting place for a new research question. Correlational methods help psychologists see how two variables of interest, like the marriage rate and economic factors described earlier, relate to one another. Psychologists use experiments to test their hypotheses and to determine the causes of behavior.

In the next sections, we will describe these common research methods used in psychological science and then compare how they might be used to approach a particular question—whether exposure to video game vio- lence increases aggression. Each method—descriptive, correlational, and experimental—provides a different view of the phenomenon in question, and each has its own particular profile of strengths and weaknesses. Each requires different types of statistical analyses, which are described in more depth later in the chapter. Many psychological studies combine several of these methods. When similar outcomes are observed using multiple meth- ods, we have even more confidence in our results.

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HOW DO PSYCHOLOGISTS CONDUCT RESEARCH? 55

Descriptive Methods

Descriptive methods include case studies, natural- istic observations, and surveys. As we have seen, personal observations and “commonsense” ideas

are especially vulnerable to bias, but descriptive methods allow a researcher to make more careful, systematic, real-world observations. Armed with these scientific observations, the researcher will be in a strong position to generate hypotheses.

The Case Study A case study provides an in-depth analysis of the behavior of one person or a small number of people. Many fields, including medi- cine, law, and business, use the case study method. Psychologists often use case studies in situations where large numbers of participants are not avail- able or when a particular participant possesses unique characteristics, as in the case described in this section. Interviews, background records, obser- vation, personality tests, cognitive tests, and brain imaging provide information necessary to evaluate the case.

One of the most productive case studies in psychology chronicled over 50 years of examinations of Henry Molaison (1926–2008), known in the scientific lit- erature as “the amnesiac patient H.M.” In 1953, Molai- son underwent brain surgery to control his frequent, severe seizures. Although the surgery may have saved his life, Molaison was left with profound memory defi- cits, which we describe in our later chapter on mem- ory. Through painstaking testing and evaluation of Molaison, psychologists learned a great deal about the brain structures and processes that support the forma- tion of memories (Corkin, 2002). Even after his death, Molaison continues to contribute to our knowledge. Researchers from MIT, the Massachusetts General Hospital, and the University of California, San Diego are analyzing Molaison’s brain at the cellular level.

How could you use the case study method to learn about exposure to video game violence and aggression? You could conduct a case study of Michael Carneal, who was sentenced to life in prison after he began shoot- ing students at his high school, killing three students and seriously wound- ing five others. Carneal had never shot a real gun before, but he was very fond of playing first-person shooter games like Doom. To conduct your case study, you gather background facts about Carneal’s case, possibly by interviewing others associated with the case, viewing legal and medical documents, and observing media accounts. You interview Carneal and possibly administer established personality and clinical tests that we dis- cuss in our chapters on personality and therapies.

descriptive method Research methods designed for making careful, systematic observations.

case study An in-depth analysis of the behavior of one person or a small number of people.

One of the most famous case studies in psychology is that of Henry Molaison (left), who was known in the literature as “the amnesic patient, H.M.” until his death in 2008. For over 50 years, Molaison allowed psychologists to evaluate his memory deficits resulting from brain surgery. After his death, scientists like Jacopo Annese (below) of the University of California, San Diego began a careful examination of Molaison’s brain.

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY56

What are the advantages of using the case study method to learn about the effects of playing violent video games on aggres- sion? School shooters are thankfully quite rare, and the case study method is well suited to learning about unusual situations. Based on the detailed data you obtain from Carneal’s case, you will be better prepared to generate and test hypotheses. A case study can also contribute to science by falsifying a hypothesis. If a hypothesis made a strong prediction that all school shoot- ings are the result of playing violent video games, finding and documenting a case of a school shooter who did not play violent video games would require rejection of the hypothesis.

Naturalistic Observation If you are interested in learning about larger groups of people than are possible with the case study method, you might pursue a naturalistic observation, or an in-depth study of a phenomenon in its natural setting. Compared to the case study method, we are now going to be looking at a much larger group of people, which will strengthen our ability to apply our results to the population in general. We also have

the advantage of observing individuals in their natural, everyday circumstances.

A classic example of the method of naturalistic observation is the careful, long-term study of chimpan- zees conducted in their habitat by Jane Goodall. In the summer of 1960, the then 26-year-old Goodall began her painstaking observations of chimpanzees living in Gombe National Park in Tanzania. Among her earlier discoveries was the fact that chimpanzees were not vegetarians, as was previously assumed:

I saw that one of them was holding a pink-looking object from which he was from time to time pulling pieces with his teeth. There was a female and a youngster and they were both reaching out toward the male, their hands actually touching his mouth. Presently the female picked up a piece of the pink thing and put it to her mouth: it was at this moment that I realized the chimps were eating meat. (Goodall, 1971, p. 34) As a result of Goodall’s years spent following the

chimpanzees, scientists have a rich, accurate knowl- edge of the animals’ behavior in the field.

Impressed by Goodall’s results, you plan to pur- sue further knowledge about violent video games and aggression by attending LAN (Local Area Network)

parties, where attendees bring their own computers to a gathering place to play multiplayer, networked video games. You hope that by observing people playing violent video games and watching their subsequent behav- ior for signs of aggression, you might reach some conclusions about the relationships between video game violence and aggression. As in Goodall’s

Jane Goodall used naturalistic observation to illuminate the world of the chimpanzee.

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Michael Carneal is now serving a life sentence in prison after he shot and killed fellow students at his high school in 1997, when he was 14.

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F O S T E R , C E D R I C 1 6 9 2 T S

To pursue the question of the effects of violent video games on aggression, you could do a naturalistic observation at a Local Area Network (LAN) party.

survey A descriptive method in which participants are asked the same questions.

sample A subset of a population being studied.

case, this approach has the advantages of providing insight into more natu- ral, real-world behaviors with larger numbers of participants.

Some naturalistic observations are conducted when people know they are being observed, while others are not. Both situations raise challenges. If we know we are being observed, we might act differently. Your LAN party participants know that aggression is not viewed positively in our culture, so they might act less aggressively when they know they’re being watched. Watching people who do not know they’re being watched raises ethical issues, which we explore in detail later in this chapter. How would you feel if you discovered you had been an unwitting participant in a study?

The use of naturalistic observation illustrates the importance of choosing a method that is well suited to your research goals. Like the case study method, naturalistic observation can be very helpful for devel- oping hypotheses, but other methods must be used to test them. Most hypotheses in psychology look at the relationships between two or more concepts, like the exposure to violent video games and aggression in our example. Testing a hypothesis would allow you to say whether or not a relationship between expo- sure to violent video games and aggression actually exists, how strong the relationship is, what direction it is, and so on. It might appear to you that the people you observe are more aggressive following their LAN parties than before, but you have no way to demon- strate your point. People engage in lots of different behaviors during LAN parties. Perhaps eating pizza or staying up all night at LAN parties enhances aggressive tendencies. With only your naturalistic observations to go on, you can’t say for sure.

The Survey Surveys or questionnaires allow you to ask large numbers of people questions about attitudes and behavior. Surveys provide a great deal of useful information very quickly at relatively little expense.

One of the primary requirements for a good survey is the use of an appropriate sample, or subset of a population being studied. Good results require large samples that are typical, or representative, of the popula- tion you wish to describe. Major poll- sters, like the U.S. Census Bureau discussed earlier, take great pains to recruit survey participants who mirror the characteris- tics of the public across factors such as gender, age, education, occupation, income, and geo- graphical location.

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY58

Surveys use self-report, so results can be influenced by people’s natural tendency to want to appear socially appropriate (Corbett, 1991). As we will discover in a later chapter on social psychology, people have strong tenden- cies to conform to the expectations of others. In some surveys, this factor is not a problem. If you ask people if they prefer lattes or mochas, you will probably get a fairly honest answer. However, in cases where people believe that their true attitudes and behaviors will not be viewed favorably by others, they are likely to lie, even when their answers are confidential and anonymous.

Let’s see how scientists have used the survey method to explore video game violence. One survey involved 1,254 middle school students attend- ing public schools in South Carolina and Pennsylvania (Olson, 2010). Although the sample did not include children from other geographic loca- tions or children who are homeschooled or attending private schools, it appears to be relatively representative of this age group. Children were asked to respond to 17 motives for playing video games on a 4-point scale from strongly agree to strongly disagree. Like all surveys, this one depends on self-report, which raises the possibility that children would give “the right answer” instead of responding honestly.

What did this scientific survey discover about violent video games? As shown in ● Figure 2.5, a surprising outcome of the survey was the more

Like to create my own world

Like to learn new things

Helps me forget my problems

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Like to “mod” games*

My friends like to play*

Like to teach others how to play

Helps me feel less lonely

Helps me make new friends

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Like the guns & other weapons*

Something to do when bored

Challenge of figuring things out*

Like to compete with others & win*

It helps me relax*

There’s nothing else to do

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It’s just fun*

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Results From a Real Survey on Video Game Use. Cheryl Olson (2010) asked middle school students why they liked to play violent video games. Over 20% of the boys agreed that the games “help me relax” and “help me get my anger out.” Source: Adapted from Olson (2010).

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shown in ● Figure 2.5, a surprising outcome of the survey was the m

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HOW DO PSYCHOLOGISTS CONDUCT RESEARCH? 59

than 20% of boys who reported using violent video games to “help me relax” and “help me get my anger out.” You will have the opportunity to take a survey on video games and aggression after you read the next section.

Correlational Methods

Correlations measure the direction and strength of the relationship between two variables, or factors that have values that can “vary,” like a person’s

height and weight. Correlations allow psychologists to explore whether hours of sleep are related to student grade point averages (Trockel, Barnes, & Egget, 2000) or if the age of parents is related to the rate of autism among their children (Reichenberg, Gross, Kolevzon, & Susser, 2011). If you’re curious about the results of these studies, the first showed that no, sleep and grade point average were not related, and the second showed that yes, age of parents is related to the rate of autism among their children.

We begin our analysis of correlations by measuring our variables. A measure answers the simple question of “how much” of a variable you have observed. After we obtain measures of each variable, we compare the values of one variable to those of the other and conduct a statistical analysis of the results. Three possible outcomes from the comparison between our two variables can occur: positive, negative, or zero correlations. In a posi- tive correlation, high levels of one variable are associated with high levels of the other variable. Height and weight usually show this type of relation- ship. In most cases, people who are taller weigh more than people who are shorter. Two variables can also show a negative correlation, in which high values of one variable are associated with low values of another. For exam- ple, high levels of alcohol consumption among college students are usually associated with low grade point averages. The third possible outcome is a zero correlation, in which the two variables do not have any systematic relationship with each other at all. When variables have a zero correlation, knowing the value of one variable does not tell you anything about the value of the other variable (see ● Figure 2.6). In spite of numerous scientific studies to the contrary, emergency room and law enforcement personnel are often convinced that they are busier with emergencies and crime on nights with a full moon. In fact, lunar cycles show zero correlations with either emergency room admissions or arrest rates (Lieber, 1978).

Correlations Describe the Direction and Strength of Relationships Between Two Variables. (a) In positive correlations, high levels of one variable are associated with high levels of another. (b) In negative correlations, high values of one variable are associated with low levels of the other. (c) In zero correlations, the two variables do not have any relationship with each other at all.

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correlation A measure of the direction and strength of the relationship between two variables.

variable A factor that has a range of values.

measure A method for describing a variable’s quantity.

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that have values that can vary, like a persons ht and weigght. CCorrelations alallolow w pssycchohologigiststs to eexploorere wwheh therr s off sleepp aree relaated to studdenent grade pooinint avverragages (TTrocockkel, Barnees,s, get, 2000000) or ifif thee aagege of paarerents is rellatt ded to ththe raratete oof auautit sm amomongng chchilldrd en (Reicchhenbererg, Groossss,, KoKolevzvzonon,, & SSusserer,, 201111).). IIf f yoyou’u’re

ouus s aabout the resusultlts of these studies, the first showed that no, sleep grade e pooini t aaverragagee were nott rrelated, and the second showedd tthat yyes, of parreentss is rerelateedd to the rattee of aaututisismm amamonong thheieir chchilildrdreen.. We begiin our analysis of corrrrelatiionons byby mmeaeasuuring oour vvarriaabblees. A A sure answers the simple queueststioion ofof ““hooww mumuchch” ofof a vvariaiabllee yoouu observed After we obtain measures of each variable we compare the

levels of another. (b) In ne correlattioionsns, hihigh vvalalueuess oo variabablee are associaateed wi lel vells oof thhe otheh r. (c)c) IInn zz coorreelattioions, tthee twwo varia nonot haveve aanyny rrelatioonsnshihipp each other at all.

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY60

Correlational research results are frequently misunderstood. Correla- tions permit us to discuss the relationships between two variables but tell us nothing about whether one variable causes changes in the other. Let us say that we discover a positive correlation between violent video games and aggression: Youth who play the most hours of violent video games have the most reports of physical aggression at school. However, we still cannot say that playing violent video games causes physical aggression at

school. This conclusion may seem very reasonable to you, and it may actually be true, so why must we abandon it? First, the two variables in a correlation can influence each other simultane- ously. Although it may be true that playing violent video games leads to physical aggression at school, youth who experience physical aggression at school may be more attracted to violent video games as an outlet for their frustration. Second, we might be observing a situation in which a third variable is responsible for the correlation we see between our two variables of inter- est. Consider the observation that many school shootings have been perpetrated by people who had been bullied relentlessly by others. Perhaps the experience of having been bullied (the third variable in this case) predisposes both a choice of violent recreation and a tendency to engage in aggressive behavior at school (see ● Figure 2.7).

If you cannot make conclusions about causality using correlations, why would you use correlations in the first place? There are a number of cir- cumstances in which correlations are more appropriate than other research methods. For example, it would be totally unethical to ask pregnant women to consume different amounts of alcohol to assess the effects of prenatal alcohol in their infants. Instead, we can ask pregnant women to identify their alcohol intake in diaries, which can then be correlated with various measures of infant functioning. Although this method will not allow us to conclude that drinking during pregnancy causes damage to the fetus, we can correctly identify the strength and direction (positive, negative, or zero) of any relationship between drinks consumed and the infants’ out- come measures (see ● Figure 2.8). Using this approach, researchers have shown that heavy maternal alcohol consumption is correlated with abnor- mal amounts of thickening of the outer layer of the brain (the cortex, dis- cussed in a later chapter on biological psychology; Sowell et al., 2008).

Choice of video game

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3rd variable problem

Aggression

Being bullied

Third Variables and Correlations. Third variables can be responsible for the correlation we observe in two other variables. In our example of video game violence and aggression, being bullied could be a third variable that predicts both choice of violent games and a tendency to be aggressive at school. The possibility of third variables is one reason we must be very careful when we reach conclusions based on correlational data.

F i g u r e 2 . 7

When you’re reading or listening to the news, watch for the use of words like link, association, or relationship used to describe two variables, such as in a headline that states “lack of sleep linked to depression” or “drinking red wine associated with lower rates of heart disease.” These key words usually mean that the data are correlational but are often mistaken for causal. Now you know how you should and should not interpret these reports.

third variable A variable that is responsible for a correlation observed between two other variables of interest.

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may actually be true, so why must we abandon it? First, the vavariabablles in aa ccorreelalationn ccanan iinflueencnce eachch ooththere ssiimulultt ouslyy. AAlthougughh itit mmaay bbee true that plplayaying g viviolent videdeo gag leadss toto physisicall agagggresesssionn aatt scchohoool, yooututh whwhoo eexpperi phphysicicalal aaggrression n aat schchooooll mamay y bbe mmoore atattrtracacteted too vvii video games as an outlet for their frustration. Second, we m be observing a situation in whwhich a third variable is respon fofor r ththee cocorrrrelelattioonn wewe sseee bbeetweweenen oourur ttwowo vvvvaariables of i eest.t. CCononsisidederr thhee obbseervvattioonn tthaat mmanny y scschhool shootings bebeenen pperrpepetrtrateded by y peopoplee wwhoho hhaad bbeeeen n bullied relentl by others Perhaps the experience of hhavavinini g been bullied

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HOW DO PSYCHOLOGISTS CONDUCT RESEARCH? 61

Dependent variable

Independent variable

No independent variable

Study and test condition

Control situational variables

Population of interest

Hypothesis Experimental group

Control group

Random representative sample

Experimental Methods

The scientist’s most powerful tool for drawing con- clusions about research questions is the formal experiment. Unlike cases in which descriptive

methods are used, the researcher conducting an experiment has a great deal of control over the situation. Unlike correlational methods, the use of the formal experiment allows us to talk about “cause” (see ● Figure 2.9).

Correlations Can Help Us Learn About Situations Where Experiments Would Be Unethical. Even though we cannot make conclusions about causes based on correlations, we can still obtain useful information. It would be unethical to assign pregnant women to drinking and nondrinking groups, but the negative correlation we see between drinks consumed by pregnant women and measures of infant mental development can tell us that drinking during pregnancy is not a good idea. The more alcohol the women consumed, the lower their children scored on tests of infant mental development. Source: Adapted from Testa, Quigley, and Eiden (2003).

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How to Design an Experiment. A good experimental design features random assignment of participants to groups, appropriate control groups, control of situational variables, and carefully selected independent and dependant variables.

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY62

n addition to using experi- mental methods, described

later in this chapter, to study our question about video games and aggression, Anderson and Dill (2000) compared responses on a standard physical aggression questionnaire (Buss & Perry, 1992) and a video game questionnaire they devised. After you complete your questionnaires, we will tell you how the college students participating in the Anderson and Dill study responded.

As you complete your question- naires, consider the limitations we raised earlier about the survey method. Physical aggression is a sensitive topic, and we suspect that the Anderson and Dill participants might have been

tempted to answer in socially appropri- ate ways that may not have been com- pletely truthful. See if you find yourself wanting to do the same.

Anderson and Dill’s Video Game Questionnaire (Anderson & Dill, 2000) asked students to rate their five most frequently played games. In the interests of time and space, we are asking you to rate only your num- ber 1 most frequently played game. Before reading further, go ahead and complete the two surverys.

Let’s add up some scores. To score the Physical Aggression Questionnaire, you first need to reverse question 7 (“I can think of no good reason . . . .”) by subtracting your score from 8. Now

add up your scores for all nine items. You do not get a single score for the Video Game Questionnaire, but it is helpful to add your scores for a–d to get a measure of “long-term exposure to video games.”

The main point of this activity is to get an idea of what it was like to be one of Anderson and Dill’s par- ticipants. We really cannot make any conclusions about the relationship between video games and physi- cal aggression based on your single scores, but you can compare your results to those reported by Buss and Perry and by Anderson and Dill.

On the Physical Aggression Questionnaire, Buss and Perry

Taking a Video Game and Aggression Survey

Experiencing Psychology

Please rate each of the following items in terms of how characteristic they are of you. Use the following scale for answering these items.

extremely uncharacteristic

of me

2 3 4 5

extremely characteristic

of me

1. Once in a while I can’t control the urge to strike another person.

2. Given enough provocation, I may hit another person.

3. If somebody hits me, I hit back.

4. I get into fights a little more than the average person.

5. If I have to resort to violence to protect my rights, I will.

6. There are people who pushed me so far that we came to blows.

7. I can think of no good reason for ever hitting a person.

8. I have threatened people I know.

9. I have become so mad that I have broken things.

Physical Aggression Questionnaire

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HOW DO PSYCHOLOGISTS CONDUCT RESEARCH? 63

reported that the average score for men was 24.3 and the average score for women was 17.9 out of a possible high of 45. If you’re curious, the sex difference in physical aggression was statistically significant, a concept we discuss later in this chapter. This concept means that we believe the sex difference observed by Buss and Perry represents a real difference, not just a chance occurrence.

Comparing your data to that of Anderson and Dill is a bit more dif- ficult, because these researchers

actually combined the Buss and Perry questionnaire with another measure of aggression in their analysis of their results. However, they found that this combined Physical Aggression score was positively correlated with long- term exposure to video game violence (a combination of a–d for exposure and e–f for violence) and with amount of recent play time (item a).

Now that you understand correla- tions, you also know what you can and cannot say about these results. Based on the results of the Anderson and

Dill correlations, we still do not know whether (a) having an aggressive personality leads to spending more time playing violent video games, (b) playing violent video games leads to more physical aggression, (c) both of these relationships are true, or (d) some third variable such as experi- ence of being bullied contributes to both physical aggression and choice of violent video games.

For the following items, rate your “most played” game:

a. In recent months, how often have you played this game?

1 Rarely

2 3 4 Occasionally

5 6 7 Often

b. During 11th & 12th grades, how often did you play this game?

1 Rarely

2 3 4 Occasionally

5 6 7 Often

c. During 9th & 10th grades, how often did you play this game?

1 Rarely

2 3 4 Occasionally

5 6 7 Often

d. During 7th & 8th grades, how often did you play this game?

1 Rarely

2 3 4 Occasionally

5 6 7 Often

e. How violent is the content of this game?

1 Little or no

violent content

2 3 4 5 6 7 Extremely

violent content

f. How bloody/gory are the graphics of this game?

1 Little or no blood

& gore

2 3 4 5 6 7 Extremely

bloody & gory

g. Which of the following categories best describes this game? Check all that apply.

__ Education __Sports __ Fantasy __ Fighting with hands/feet __ Fighting with weapons __ Skill

Video Game Questionnaire

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY64

A researcher begins designing an experiment with a hypothesis, which can be viewed as a highly educated guess based on systematic observations, a review of previous research, or a sci- entific theory. A hypothesis takes this form: “If I do this, that will happen.” To test the hypothesis, the researcher manipulates or modifies one or more variables and observes changes in oth- ers. The variable controlled and manip- ulated by an experimenter (“If I do this . . . .) is known as the independent variable. We need some way to evaluate the effects of this manipulation. We use a dependent variable, defined as the observed result of the manipulation of the independent variable, to tell us “that will happen” as a result of the inde- pendent variable. Like the independent variable, our choice of dependent vari- able is based on our original hypothesis.

After determining our independent and dependent variables, we still have quite a bit of work to do. In most experi- ments, we want to know how simply

going through the procedures of being in an experiment influences our dependent variable. Perhaps the hassle of going to a laboratory and filling out paperwork changes our behavior. To evaluate these effects, we assign some of our participants to a control group, or a group that experiences all experimental procedures with the exception of exposure to the inde- pendent variable. The experience of the control group should be as similar as possible to that of the experimental groups, who do experience the independent variable.

We want to ensure that our dependent variables reflect the outcomes of our independent variables, instead of individual differences among the participants’ personalities, abilities, motivations, and other similar fac- tors. To prevent these individual differences from masking or distorting the effects of our independent variable, we randomly assign participants to experimental or control groups. Random assignment means that each participant has an equal chance of being assigned to any group in an experiment. With random assignment, any differences we see between the behavior of one group and that of another is unlikely to be the result of the individual differences among the participants, which tend to cancel each other out.

Individual differences among participants are an example of confound- ing variables, or variables that are irrelevant to the hypothesis being tested that can alter our conclusions. For example, a researcher might want to test

independent variable An experimental variable controlled and manipulated by the experimenter; the “if A happens” part of a hypothesis.

dependent variable A measure that demonstrates the effects of an independent variable; the “result” part of a hypothesis.

control group A group that experiences all experimental procedures with the exception of exposure to the independent variable.

experimental group A group of participants that is exposed to the independent variable.

random assignment The procedure in which each participant has an equal chance of being assigned to any group in an experiment.

confounding variable Variables that are irrelevant to the hypothesis being tested that can alter a researcher’s conclusions.

Researchers attempt to reduce the impact of confounding variables on their results. In a test of the effects of aerobic exercise on blood pressure, situational confounding variables, such as (1) traffic outside the building, (2) a noisy treadmill, and (3) a neighbor breathing heavily, can be controlled by holding the environment as constant as possible for all participants. Individual differences, such as (4) an early morning after little sleep or (5) superior fitness, can be controlled by randomly assigning participants to groups.

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HOW DO PSYCHOLOGISTS CONDUCT RESEARCH? 65

the effects of aerobic exercise on blood pressure. If some of the participants competed in triathlons without the researcher’s knowledge, their athletic experience would confound the interpretation of the results. Random assignment to groups typically controls for confounds due to these types of individual differences, but other sources of confound exist. Situational confounds, such as time of day or noise levels in a laboratory, could also affect the interpretation of an experiment. Scientists attempt to run their experiments under the most constant circumstances possible to rule out situational confounding variables.

Let’s return to our question about violent video games and aggression, and see how one real experiment addressed the issue. The researchers tested a hypothesis stating that playing a violent video game (the indepen- dent variable) would produce higher aggression (the dependent variable) (Anderson & Dill, 2000). The experimental group played a violent game (Wolfenstein 3D) while the control group played a nonviolent game (Myst). Participants were randomly assigned to groups. You can imagine how the results might be distorted if the experimental group consisted of football players and the control group consisted of members of the chess club. Following their game playing, participants had an opportunity to apply a blast of noise to another person, and the length of the noise blast served as the dependent variable. We’re assuming that laboratory conditions were held constant to avoid situational confounds. For example, we know that people feel more aggressive in hot temperatures (Carlsmith & Anderson, 1979). What would happen to our experiment if the air conditioner in the laboratory broke while participants played violent video games, but was fixed right before the next participants played nonviolent games? Results of this carefully controlled experiment confirmed the researchers’ hypothesis: Playing the violent game led to the administration of longer noise blasts to another person (see ● Figure 2.10).

Experimental Method in Action. Anderson and Dill (2000) randomly assigned participants to groups playing violent and nonviolent video games. After playing, each participant was given the opportunity to administer a blast of noise to another person. Keeping conditions in the laboratory as constant as possible would help to reduce the impact of situational variables.

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Dependent variable: Noise blast duration

No independent variable:

Nonviolent video game

Independent variable:

Violent video game

Study and test condition

Control situational variables

Hypothesis: Playing violent video games

produces higher aggression

Population of interest: College students

Experimental group

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY66

As powerful as it is, the experimental method, like the other methods discussed previously, has some limitations. Experiments can be somewhat artificial. Participants know that they are in a research study, and they may vary their behavior as a result. However, making a laboratory experiment more realistic can raise ethical challenges. In a study conducted in 1962, before current ethical guidelines for research had been adopted, military person- nel were led to believe that their lives were really in danger so that experimenters could “realistically” assess the effects of panic on performance (Berkun, Bialek, Kern, & Yagi, 1962). Although the responses of these participants were probably quite representa- tive of “real life,” few of us would want to be put in their position. This type of research could not be conducted under today’s ethical standards, described later in this chapter.

Artificiality is also a problem in the Anderson and Dill video game study. Our real-world question relates to the likelihood that playing violent video games may elicit real physical violence in real situations. Is a person’s willingness to inflict a loud sound on another person in a professor’s laboratory truly representative of the type of violence involved in school shootings like Michael Carneal’s? It may or may not be, but we need additional research to find out.

Another issue with the experimental method arises from dif- ferences in the choices of independent and dependent variables. Independent (controlled) and dependent (measured) variables have to be defined and implemented in some concrete fashion. The pro- cess of translating abstract independent and dependent variables

into concrete forms is called operationalization. There are many ways we can operationalize our variables in practical terms. Anderson and Dill operationalized aggression in terms of how lengthy a sound blast a person was willing to inflict on another person. Other researchers might choose different ways to operationalize aggression, such as frequency of physical fights among preschoolers. As a result, even though there is a large body of work regarding the impact of violent video games on aggression, the meth- ods used are so different that few direct comparisons can be made among the many studies.

Meta-analyses The point of this discussion is not to convince you that sci- entists don’t know what they’re talking about, but rather to impress upon you the importance of reviewing research results using your best critical thinking skills. In seeking to understand something as complicated as the science of mind, it is unlikely that any single study could provide complete information about a phenomenon. Instead, progress in our understanding results from the work of many scientists using diverse methods to answer the same question. Conducting a meta-analysis, or a statistical analysis of many previous experiments on the same topic, often provides a clearer picture than single experiments observed in isolation. As shown in ● Fig- ure 2.11, a meta-analysis of about 300 studies, using diverse methods and over 54,000 participants, demonstrated a positive relationship between video game violence and aggression (Anderson & Bushman, 2001).

To conduct an experiment, we must carefully operationalize, or define our variables in practical terms. One way to operationalize physical aggression is to measure how often a preschooler has a physical fight with others.

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operationalization Defining variables in practical terms.

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HOW DO WE STUDY THE EFFECTS OF TIME? 67

The research discussed through the remainder of this textbook has been subjected to considerable skeptical review by the researchers’ peers. Most has stood the dual tests of peer review and replication by others. Converging evidence from descriptive, correlational, and experimental research provides us with confidence in our conclusions. Psychology, like any science, has followed its share of wrong turns and dead ends, but the vast majority of the knowledge presented here has been carefully crafted to present the most accurate view possible of behavior and mental processes.

How Do We Study the Effects of Time? Modifications of the methods discussed previously might be necessary for answering specific questions. Psychological scien- tists frequently ask questions about normal behaviors related to age. As we will see in our chapter on development, aggression in preschoolers means something different than aggression in a 16-year-old. Considering the impact of video game violence on aggression within the context of age-related change adds a new and useful dimension to our hypothesis, but requires additional attention to the research methods to be used.

Psychologists have three specific techniques for assessing the normal behaviors associated with age: cross-sectional, longitudinal, and mixed lon- gitudinal designs. To do a cross-sectional study, we might gather groups of people of varying ages and assess both their exposure to violent video games and their levels of physical aggression. We might be able to plot a

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Insights From Meta-analyses. Combining the findings of over 300 studies representing more than 50,000 participants, Anderson and Bushman (2002) argue that a positive relationship exists between exposure to video game violence and aggression, aggressive cognitions, aggressive affect or mood, and arousal. Video game violence was negatively correlated with helping behaviors. This type of graph is known as a boxplot. The width of each box corresponds to the number of studies of each type. Twenty-five percent of the results fall below the bottom of the box and another 25% are above the top of each box. The line in the middle of a box shows the median, which we define later in this chapter as the point where half of the data are above and half below. Source: Adapted from Anderson and Bushman (2001).

F i g u r e 2 . 1 1

Cross-sectional studies usually show that intelligence scores decrease with age. These results are most likely a cohort effect. Performance on IQ tests has risen approximately 3 points per decade over the past 100 years for reasons that are not fully understood (Flynn, 1984).

cross-sectional study An experimental design for assessing age-related changes in which data are obtained simultaneously from people of differing ages.

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY68

developmental course for age-related differences in both video game expo- sure and aggressive behavior. However, the cross-sectional method intro- duces what we refer to as cohort effects, or the generational effects of having been born at a particular point in history. Being 20 years old in 1950 was very different from being 20 years old in 1980 or in 2010, due to a variety of cultural influences. Today’s 10-year-olds, who do not know of a time with- out the Internet, might respond very differently to violent video games than might today’s 40-year-olds for reasons that have nothing to do with age. Any such cohort effects could mask or distort our cross-sectional results.

A method that lessens this dilemma is the longitudinal study, in which a group of individuals is observed for a long period (see ● Figure 2.12). One of the longest running longitudinal studies is the Fels Longitudinal Study, currently housed in the Wright State University School of Medicine. This study began in 1929 to observe the effects of the Great Depression on children, but now has enrolled great-grandchildren of the original partici- pants. To use the longitudinal method to answer our question, we could start with a group of infants and carefully plot their exposure to violent video games and their levels of physical aggression into adulthood. The longitudinal approach has few logical drawbacks, but it is expensive and time-consuming to do. Participants drop out of the study due to moves or lack of incentive. Researchers then must worry about whether those who remain in the study still comprise a representative sample.

The third approach, the mixed longitudinal design, combines the cross-sectional and longitudinal methods. Participants from a range of ages are observed for a limited period of time, usually about five years. This approach is faster and less expensive than the longitudinal method and avoids some of the cohort effects of the pure cross-sectional method.

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Verbal memory Verbal ability Perceptual speed

Special Designs Let Us See Behaviors Associated With Age. Longitudinal designs control for the cohort effects that are often seen in cross-sectional designs. This longitudinal study shows that verbal ability and verbal memory are fairly stable over the lifetime, but that perceptual speed gradually worsens with age. Source: Adapted from Schaie (1996).

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longitudinal study An experimental design for assessing age-related changes in which data are obtained from the same individuals at intervals over a long period.

mixed longitudinal design A method for assessing age-related changes that combines the cross-sectional and longitudinal approaches by observing a cross-section of participants over a shorter period than is used typically in longitudinal studies.

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69HOW DO WE STUDY THE EFFECTS OF TIME?

Summary 2.2 Principles of Research Methods

Research method Strengths Weaknesses

Descriptive methods

Case study Can explore new and unusual phenomena; can falsify a hypothesis

Limited generalization

Naturalistic observation Provides insight into natural, real-world behaviors

Participants act differently when watched; ethical issues

Survey Provides large amounts of data quickly and inexpensively

Requires large representative sample; people wish to appear socially appropriate and may lie

Correlations

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Allow us to predict behavior; stimulate development of hypotheses; address some difficult ethical situations

Cannot be used to discuss causality

Experiments Control of situations and strong hypothesis testing; allow for judgments of causality

Artificiality, ethical concerns, time- consuming

Assessing the effects of time

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Cross-sectional study Quick and relatively inexpensive Subject to cohort effects

Longitudinal study Reduces impact of cohort effects Expensive, time-consuming; people drop out

Mixed longitudinal study Less expensive and time-consuming than longitudinal with some control of cohort effects

Still relatively expensive and time- consuming; drop-out problem remains

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY70

A valid measure actually measures what it is supposed to measure. In this case, your bathroom scale is supposed to tell you how much you really weigh.

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validity A quality of a measure that leads to valid conclusions (i.e., the measure measures the concept it was designed to measure).

reliability The consistency of a measure, including test-retest, inter-rater, inter- method, and internal consistency.

How Do We Draw Conclusions From Data? Asking the right questions and collecting good information are only the beginning of good science. Once we have collected our results, or data, we need to figure out what those data actually mean for our hypotheses and theories. The interpretation of data is not an arbitrary act—scientists follow specific rules when drawing their conclusions.

The Importance of Valid and Reliable Measures

Data are only as good as the measures we use to obtain them. How would we know whether a mea- sure is good or bad? Two standards that any mea- sure must meet are validity and reliability.

Validity means that a measure leads to valid conclusions, or actually measures the concept it is designed to measure. For example, your bathroom scale is supposed to measure how much you weigh. The data obtained from your bathroom scale can lead you to a valid conclusion (this is how much I really weigh) or an invalid conclusion (oh wow, I’m much lighter than the doctor’s scale said I am).

How would we determine whether a measure leads to valid conclu- sions or not? One approach is to see if a measure correlates with other existing, established measures of the same concept. Many universities use the SAT I to help select the best candidates for admission. This test is sup- posed to measure a student’s aptitude for success in college, but some uni- versities have abandoned it in favor of other measures. We could ask which of the following measures—the SAT I, SAT II single subject achievement tests, or high school grade point average—shows the highest positive corre- lation with first-year college grades. The results of this comparison indicate that the SAT II shows the highest positive correlation with first-year college grades compared to both the SAT I and the high school grade point average (Geiser & Studley, 2001). Thus, we can conclude that the SAT II is the most valid of the three measures for predicting first-year college grades.

Reliability refers to the consistency of a measure. There are several differ- ent meanings of reliability in science, including test-retest, inter-rater, inter- method, and internal consistency. The test-retest reliability of the SAT I is quite good, as you might have noticed if you took the test more than once. If you were ill for the first test, or you invested in a preparation course before taking it the second time, your score might change, but otherwise, your scores are very likely to be about the same. Good measures also show high inter-rater reliabil- ity, or consistency in the interpretation of a measure across different observers. You can imagine how distressing it would be if one lab identified you as having a fatal disease on the basis of a blood test and another did not. Inter-method reliability describes the positive correlation of several approaches to measure a feature in an individual. Even though we said previously that the SAT II is the most valid predictor of your first-year college grades, it is likely that your SAT I, SAT II, and high school grades are all positively correlated. Finally, internal consistency results from measures within a single test that positively

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HOW DO WE DRAW CONCLUSIONS FROM DATA? 71

correlate with each other. Earlier in this chapter, you had the opportunity to complete a survey. Often, students taking tests like this for the first time complain that they are “answering the same question over and over again.” In a sense, this is true, because most tests include a number of items related to the same concept to see if the participant answers them in similar ways, which allows the researcher to assess the test’s internal consistency.

Reliability is not the same thing as validity. You can obtain a consistent result (reliability) that lacks meaning (validity), but a measure cannot be valid without also being reliable. For example, if you weigh 200 pounds, and your bathroom scale consistently reports that you weigh 150 pounds whether you’re looking at the number yourself or your roommate reads it for you, the scale has reliability but not validity. If you get a wildly different number each time you step on the scale, you have neither reliability nor validity. The measure is not consistent (no reliability) and fails to measure the construct—weight in this case—that it is designed to do (no validity).

Descriptive Statistics

Just as we might explore a new research topic using the descriptive research methods outlined earlier, we can use descriptive statistics to explore the charac-

teristics of the data we obtain from our research. Descriptive statistics help us organize individual bits of data into meaningful patterns and summaries. For example, research investigating the ability of the SAT I, SAT II, and high school grades to predict college grades in colleges and universities across the country would be overwhelming in the absence of some way of summa- rizing the individual data points for tens of thousands of students in mean- ingful ways. Descriptive data tell us only about the sample we have studied. To determine whether the results from our sample apply to larger popula- tions requires additional methods, described in a subsequent section.

We might approach this mass of data first by asking how the scores and grades are distributed. We could arrange SAT I scores from high to low and note how many students obtained each score. The result of our work would be a frequency distribution. We often illustrate frequency distributions with a bar chart, or histogram, like the one shown in ● Figure 2.13.

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descriptive statistics Statistical methods that organize data into meaningful patterns and summaries, such as finding the average value.

Frequency Distributions. Descriptive statistics, such as these frequency distributions of SAT I mathematics scores, allow us to see meaningful patterns and summaries in large sets of data. Source: Adapted from The College Board

(2009).

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ganize indiiviv duaal bits of data into meaningful patterns and summaries. xamplp e, ressearchh investigatinng g ththe e aba illitity y ofof thee SSATA II, SAS T T IIII,, anand d highh ol ggradess to preddict collegee ggrades in ccolollelegess anand d ununivererssities acrososss ountry would d bbe oovverwrwhelmminng in the absbsencee oof sosomeme wwayay off susummmma-a gg tthhe iindividuall ddata ppoints foforr tetensns of f ththouousandnds off sstutudentntss inin mmeaean-

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY72

Central Tendency Frequency distributions are a useful starting place, but we might also be interested in identifying the “average” score on our mea- sures, or the central tendency of our data set. There are three types of mea- sures for central tendency: the mean, median, and mode for each group of

scores. The mean is the numerical average of a set of scores, computed by adding all scores together and dividing by the number of scores. For all students tak- ing the SAT in 2009, the mean on the critical reading section was 501, the mean on the mathematics sec- tion was 515, and the mean on the writing portion was 493.

The median represents a halfway mark in the data set, with half of the scores above and half below. The median is far less affected by extreme scores, or outliers, than the mean. In our SAT data, the median scores are quite close to the means: 500 for critical reading, 510 for mathematics, and 490 for writ- ing. Why then, would you ever need to consider a median? In some sets of results, you might find some very extreme scores that could affect the mean. For example, if you asked employees at a small business

to report their current annual salaries, you might get the following results: $40,000, $45,000, $47,000, $52,000 and $350,000 (we’re assuming this is the boss). The mean in this example would be $106,800, but that figure doesn’t really provide a good summary of these numbers. The median, $47,000 in this case, is more representative of your overall results. Take a look at ● Fig- ure 2.14 for another example.

The mode refers to the score that occurs most frequently and is easy to determine from looking at a histogram. We do not have exact numbers for modal scores on the SAT, but we can tell you that the most frequent range of scores is between 400 and 490 for all three tests (critical reading,

Many colleges and universities use the SAT or other standardized tests to predict success in college courses. Evaluating the resulting data is easier if we use descriptive statistics to summarize the performances of the many thousands of individual students who take the tests.

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mean The numerical average of a set of scores.

median The halfway mark in a set of data, with half of the scores above and half below.

mode The most frequently occurring score in a set of data.

What New Information Can We Learn From a Median? In many cases, like the SAT data, means and medians are very close together. However, in other cases, like reported lifetime sex partners, these two measures of central tendency provide very different pictures. The average number of sex partners for males is 20, but half of all men report having had 8 or fewer partners. This suggests that the upper half of males have a very large number of partners indeed. Source: Adapted from ABC News: Primetime (2001).

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example, if you asked employees at a small bus to reporort t ththeie r cucurrrrenent aannun al ssala arieies,s, yyouou migghtht get thehe ffolollolowingng rreses $40,00000, $45,0000, $4$47,7 0000,0, $$525 ,00000 annd $$350,00000 (w(we’ree aassumingg thhisis i boss). ThThe meann iin hthis eexxampmplle wououldd bbe e $1$10606,8,80000,, bubutt thhatat fifiguuree ddo rreally pprorovividede a ggooood d suummmarryy of thehese nnumumbbers. ThThe mmedediaiann, $$4747,0,0 this case, is more representative of your overall results. Take a look at ● ure 2.1414 for another exampple.

Thee modede rerefef rsrs ttoo ththe scoore e ththaat occcururs momostst ffrerequququeently and is to deteermminene ffrom loookokiingg at a hhisttogrgramm. WeWe ddo nonott hhave exact num for moodadall sscororeses on n ththee SASAT, bbut we cacan ttell youou tthahat t the most freq range of scores is between 400 and 490 for all threeee tteests (critical rea

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mathematics, and writing). The usefulness of the mode depends on the research question you are asking. In the case of the SAT, the mode doesn’t provide very interesting information, so let’s return to our drinking data mentioned earlier in the chapter. In this case, the mode among Ameri- can adults is to drink zero to one drink per week. Seventy-two percent of American adults report this amount of drinking. In response to this find- ing, the U.S. Department of Justice recommended reducing problem drink- ing by raising taxes on alcohol (U.S. Department of Justice, 2002). These increased taxes would have little to no effect on nearly three quarters of American adults. The taxes would precisely target those whose behavior the government wants to change (the 23% who are heavy drinkers) while barely inconveniencing the vast majority of the population.

Using the mode is also an advantage over the use of a mean or median when there is more than one mode in a set of data. For example, the mean age of onset for the eating disorder anorexia nervosa, which we discuss in our chapter on motivation, is 17 years of age, but the distribution is bimodal, which means it has two substantial modes. One peak occurs around the age of 14, when many teens struggle with their changing shapes, and another occurs around the age of 18, when many teens leave home and make their own food choices without the watchful eyes of their parents (Halmi, Casper, Eckert, Goldberg, & Davis, 1979). An intervention program designed to coincide with the most likely ages of onset would probably be more effective than one timed to coincide with the mean age of onset (see ● Figure 2.15).

Variability In addition to being curious about central tendency, we might also want to know how clustered our scores are. The traditional way to look at the variability of scores is to use a measure known as the standard deviation. This measure tells you how tightly clustered a group of scores is

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What New Information Can We Learn From a Mode? The average age of onset for the eating disorder anorexia nervosa is 17 years, but this measure masks the important fact that age of onset shows two modes— one at 14 years and the second at 18 years. For public health officials wishing to target vulnerable groups for preventive education, the modes provide better information than the mean. Source: Adapted from Halmi (1979).

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variability In statistics, the extent to which scores differ from one another or from their mean; often measured using the standard deviation.

standard deviation A measure of how tightly clustered a group of scores is around their mean.

It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. —Sir Arthur Conan Doyle (Sherlock Holmes)

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nts (Halmi, , Caspper, Eckert, Goldberg, & Davis, 1979). An intervention ram designned too coincide wwitith h ththe momostst likelely y agess of ononseset t wwould d ablyy be mmorre effeffective thann oone timedd ttoo coc inncicidede wwitth ththe mean agege

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY74

around the mean. A smaller standard deviation suggests that most of the scores might be found near the mean, whereas a larger standard deviation means that the scores are more spread out away from the mean. Return- ing to our salary example, we had five salaries with a mean of $106,800. To obtain the standard deviation, which is easy to do with a calculator, you subtract each score from 106,800, square each difference (to eliminate any minus signs), add the squares, divide the total by 5 (the number of scores), and take the square root of the result. In this case, we end up with a standard deviation of 136,021, which means that our average difference between a score and the mean of the scores is 136,021. If we discard our extreme score ($350,000) and find the standard deviation of the remaining 4 scores, it turns out to be much smaller: 4,966.56. These results suggest that the distribution of the first four salaries is tightly clustered, whereas the distribution of all five salaries is more spread out.

The Normal Curve Many measures of interest to psychologists, such as scores on intelligence tests, which we discuss in a later chapter on cogni- tion, appear to form a normal distribution, illustrated in ● Figure 2.16. The ideal normal curve in this illustration has several important features. One, it is symmetrical. Equal numbers of scores should occur above and below the mean. Second, its shape indicates that most of the scores occur near the mean, which is where our measure of variability plays a role. In the standard normal curve, shown in (a), 68% of the population falls within one standard deviation of the mean, 95% falls within two standard deviations, and 99% of the population falls within three standard deviations. Instruments for assess- ing intelligence, discussed in a later chapter on cognition, frequently convert

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The Normal Curve. Many measures of interest to psychologists take the approximate form of a normal distribution. This figure compares a standard normal curve, shown in (a), to the distribution of scores on a standardized test of intelligence, the Wechsler Adult Intelligence Scale (WAIS-IV), shown in (b).

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normal distribution A symmetrical probability function.

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the mean. Second, its shape indicates that most of the scores occur nea mean, whwhicich h is wwheherere ouur mmeasusure ooff vavaririabability plplaya s a rorolele.. InIn thee sstatann normmalal curve, shhowown n in (a)a), , 686 %% off thhe ppoppulattioionn faf llss wwithin onee sstatann deviattioon of the mmean, 95%5% ffalallsls wwitthihin twtwo stanandadardd ddeveviatitiononss, aandd 99 tthe popupulalatitioon falallsls wwithiinn threeee sstandadardrd ddeveviaiattions.s. IInstrtrumumenents fforor aass ing intelligence, discussed in a later chaptp er on cognition, frequently con

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raw scores earned by many participants to fit a normal distribution having a mean of 100 and a standard devia- tion of 15. As a result, we would expect 68% of test-takers to receive an IQ score between 85 and 115. Ninety-five percent will score between 70 and 130, leaving only 2.5% to score above 130 and another 2.5% to score below 70.

Descriptive Statistics With Two Variables In our dis- cussion so far, we have been describing single variables, such as number of drinks consumed, salaries, and SAT scores. In psychological research, we often want to describe the relationships between multiple variables.

We can illustrate the relationship between two vari- ables in a scatter plot, like the one shown in ● Fig- ure 2.17. Each dot represents the intersection between scores on two variables of interest. For example, we can compare the distributions of SAT scores as a function of grade point average (GPA). From our scatter plot, it looks like SAT scores and GPAs are systematically related to each other. As one increases, the other does as well, which you should recognize from our earlier discussion as a positive correlation.

Although our scatter plot gives us a sense that GPAs and SAT scores have a systematic relationship, we can compute that relationship exactly using a correlation coefficient. Correlation coefficients can range from �1.00 to �1.00, with a correlation of �1.00 and a correlation of �1.00 being equally strong but differing in the direction of the effect. A zero correlation indicates the two variables have no systematic relationship at all. The farther away a correlation coefficient is from zero, the stronger the relationship between the two variables. When the number is positive, this means that we have a positive correlation; when one factor occurs, the other is very likely to occur, too. Earlier in this chapter, we referred to height and weight as a common example of a positive correlation. In a negative correlation, indicated by a correlation coefficient with a minus sign, as one factor increases, the other decreases. Our previous example of a negative correlation is the amount of alcohol consumed and a student’s grade point average (GPA). As alcohol consumption increases, the GPA decreases.

Inferential Statistics

Although we can learn a great deal from our descriptive statistics, most of the research described in this textbook fea-

tures the use of inferential statistics, so called because they permit us to draw inferences or conclusions from data. The descriptive statistics described earlier allow us to talk about our sample data, but do not allow us to decide what our sample data might mean more generally. To reach conclusions about how our observations fit the big pic- ture, we use inferential statistics.

On the 2009 SAT I mathematics test, men scored an average of 534 and women scored an average of 499. Does this mean that men perform better

A Scatter Plot. A scatter plot allows us to visualize the relationship between two variables, such as the math SAT score and high school grade point average (GPA) for one small sample of college students. This relationship should look familiar to you—it is an example of a positive correlation. Source: Adapted from Young (2011).

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Most universities now publish “25–75” SAT data from their most recently enrolled students. The higher your scores are above the 25% mark, the better your chances of being accepted. The 25% mark on the reading test for Harvard was 690, but only about 3% of all test-takers score 690 or above. You probably need to be in that top 3% or so of test-takers if Harvard is your school of choice.

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er discussioon as a a positive correlation. Althououghgh ouur scaatter plot givevess usus a senensese thaat GPG Ass andd SSATAT sscoreess

a ssysystemmatiic relalationship, wwe can comompupute tthahatt rer llattiononsshipip eexax cttlyly g a correlatioi n cocoeffiefficic ent. CCorrelationon coefficfficientntss ccann rar ngee fromom 00 to ��1.00, wiitth a ccoorrelatiionon ooff �1.1 0000 aandd aa correrelationon oof f �1.1 000

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us to visusualalizizee the rerelalatitionon betweeeenn ttwo vav riabblees, su mam thh SSAT sscocorere andd hhiighh s grgradee popoint avverage ((GPA smsmall sasampmplele ooff collllegegee stst relationship should look fa you—it is an example of a cocorrr elelatatttioioionn. Source: Adapted (202011)11).

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Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY76

SP stands for extrasensory perception, with extra in

this case meaning “outside” the boundaries of the normal infor- mation we obtain from our various senses, such as vision, hearing, and touch. The study of ESP is part of a larger field of parapsychology, or the study of psychic phenomena lying outside the typical boundaries of the field of psychology described in our first chapter. Among the abilities grouped as ESP are telepathy (the ability to communicate with other minds without using the usual meth- ods of speaking or writing), clairvoy- ance (the ability to perceive objects that do not affect the known senses), precognition (knowledge of future events), and premonition (emotional anticipation of future events). In 2005, Gallup pollsters found that 41% of Americans said they believed in ESP, with 25% not sure, and 32% not believing (Gallup poll news ser- vice, 2005). Ninety-six percent of the scientists who are members of the National Academy of Sciences do not believe in ESP. A recent study of ESP (Bem, 2011) has generated considerable

Do You Believe in ESP?

Connecting to Research

Popular shows like Ghost Hunters might contribute to the large number of Americans who report a belief in ESP (41%). In contrast, 96% of the members of the National Academy of Sciences do not believe in ESP.

discussion in the scientific com- munity about everything from the statistics we use to the effects of investigator bias. Evaluating this study provides you a good opportu- nity to practice your critical thinking skills and to apply what you have learned about validity and reliability.

The Question: Nine experiments involving more than 1,000 participants tested different types of precognition and premonition. We will focus our attention on the first experiment, which tested the following hypothesis: participants should be able to anticipate the position (right side or left

side of a computer screen) of an erotic photograph (see ● Figure 2.19).

METHODS One hundred undergraduates (50 men and 50 women) participated. Stimuli, both erotic and nonerotic photographs, were selected from a standard set known as the Inter- national Affective Picture System. On each trial, participants saw two curtains on the computer screen and were asked to predict which curtain hid a picture. The sequencing of the erotic and nonerotic pictures and the

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than women on this test? Or do men and women perform similarly, and this group is just an unusual sample of test-takers? To resolve these questions, we test the hypothesis that men score higher than women on the math por- tion of the SAT I. Recall that we cannot “prove” a hypothesis to be correct, but we can demonstrate that the hypothesis is false (see ● Figure 2.18).

How do we know when a hypothesis should be rejected? Like most sciences, psychology has accepted odds of 5 out of 100 that an observed

P stands for extrassensory ercepptit on, wiith extrtra in is caase meeaninng “ouutside” ries of f ththe normrmal inffoor-- obbtatainin from our vavarious hh as vivision, hearinng,g, andnd stut dyy ooff ESE P iss ppara t of a of parrapsyychoollogy, or the ychic pphennomenana llyiying typical boundaries of psychology described in

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discussion in the scientific com- muuninityty aabob utt eeveveryrything g frf om thhe sttattistics we ussee toto thee eeffeffectc s oof innveestigator bbiaas. EEvaluuatingg ththiss stududy y prprovovidees yyouou a gooood opppoportu- nity to practice your critical thinking skilillsls and to apply what you have leaarnned abbououtt valilididityty andd rreleliaiabibililityty.

Thhe Quesstiionon:: NiNinene eexpx eerimimentss invovolvlviningg momorere tthahann 1,1,00000 0 pparticcipipantsts tested different types of precognition

sis de of f a coc mputterer sscrcreeeen) oof anan ee php otogograraphph (seee ●●● Figug re 2.19)9).

MMETETHHODSDS One hundred undergraduates (5 men and 50 women) participate StStimimululi,i bbotothh ererototototiciici and nonerot phphotogograaphphss, wwere selected from aa sstannddardrd ssetet kknown as the Inte national AAffeffectctivve Picture System

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left-right positions was determined by a random number generator after the participant made his or her selec- tion. This timing was designed to test the precognition of future events (the participants selected a side of the screen before the random number generator selected a location for the picture).

Here is where Bem’s methods get a bit murky. The first 40 participants saw 12 erotic pictures, 12 negative pictures (unpleasant images), and 12 neutral pictures. Then for reasons not well explained in the paper, the method was changed for the remain- ing 60 participants. These partici- pants saw 18 erotic and 18 nonerotic photos, 8 of which were described as “romantic” but not erotic (couple at a wedding, etc.). It is quite unusual for researchers to change their methods in the middle of an experiment and more troubling when there doesn’t seem to be a good reason to do so.

RESULTS Normally, if we have two choices, we have a 50% chance of guessing correctly on each trial. Bem reported that the future position of the erotic images was chosen correctly on 53.1% of the trials, and the future position of the nonerotic images was chosen

correctly on 49.8% of the trials. Bem reported that his results were statis- tically significant, or, in other words, very unlikely to happen just due to chance.

CONCLUSIONS Bem concluded that the choices made by his participants were better than chance, supporting his hypoth- esis that precognition could be demonstrated.

What do others think of Bem’s results? James Alcock, writing for the Skeptical Inquirer, concludes that “just about everything that could be done wrong in an experiment occurred

here” (Alcock, 2011). Among Alcock’s concerns were Bem’s changing of his method midway through the experi- ment and his questionable use of statistical analyses. As we discussed earlier, replica- tion provides an important check on possible researcher bias, and failure to replicate indicates serious flaws in an experiment. So far, the three known replications of Bem’s experi- ments have failed to produce sig- nificant results. In spite of the flaws, however, Bem’s experiments have contributed to science by stimulating a lively discussion of scientific and statistical methods.

Evidence of ESP? Participants in Bem’s study were supposed to predict behind which of two curtains a picture would appear.

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result is due to chance as an acceptable standard for statisti- cal significance. We can assess the likelihood of observing a result due to chance by repeating a study, like throwing dice multiple times. We could give the mathematics portion of the SAT to 100 randomly selected samples of male and female college- bound students. If in 5 or more of the 100 samples, men and women score about the same or women score higher than men, we would reject our hypothesis as false.

statistical significance A standard for deciding whether an observed result is due to chance.

Many populations that are interesting to psychologists are unable to sign informed consent forms legally and require additional ethical protection. In the case of research with infants, parents are required to sign informed consent forms on their child’s behalf.

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This type of careful analysis of the SAT data has confirmed that the dif- ferences on the mathematics portion of the test between male and female test-takers is, in fact, statistically significant (Halpern et al., 2007). Does this result mean that we should consider this difference when deciding on a major or career? Probably not. Keep in mind that the goal of the SAT is to predict college grades. If you compare the SAT scores of men and women receiving the same letter grade in a mathematics course at the very same school, the women have scored 33 points less on the math SAT than the men (Wainer & Steinberg, 1992). This is just about the same difference that we observed between the mean scores of men and women on the SAT I math test. It appears that for some unknown reason, the SAT might be under- estimating women’s ability to achieve in college mathematics courses.

How Can We Conduct Ethical Research? We mentioned earlier that deceiving participants into thinking they were truly in danger raised ethical questions. On what basis do researchers decide what they can and cannot do to their research participants?

Although the vast majority of studies published in psychological jour- nals involve the use of human participants, psychology also has a rich heritage of animal research. Consequently, separate guidelines have been developed for each type of subject. Researchers working in universities and other agencies receiving federal funding must receive the approval

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Are Male and Female Scores on the Math SAT Really Different? Inferential statistics allow us to decide whether the observed differences between the performance of males and females on the math SAT represents a real gender difference or is just due to chance. Source: Adapted from The College Board (2009).

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ThThis s type of caareful ananalysysisis oof ththee SATT daatata hhasa cconnfirfi meedd thhatt the fferencess oonn tthe mamaththemmaatics poportion n ofof tthhe tteest beetwtween n mamalle aandnd ffee test-takkere s is, in fact, statistically signinificfi ant (Halpern et al., 2007). D this ressuult meeanan thaatt wewe shohoululd d coconsnsidderer tthihiss did ffererencncee whwww en decidin a majoor or carareeeer?r? PProrobabablly nott. KKeeepp iin mminnd ththatat tthee ggoal of the SAT predictt cocollllegegee grgraddeses. Iff yyoou comompparre thehe SSATT scocoreress of men and wo receiving the same letter grade in a mathematicss ccouursrse at the very s

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d Female Scorres on tthe Math SAT Really Different? Inferential statistics allow us to decide whether the observed etween the perrformannce of males and fefemamaleless on tthehe mmata h SAATT repressenents a reaeall gegendnder differerene ce or is jjusustt dudue e to cchahancncee d fromm The CoCollege e Board (20( 09).

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HOW CAN WE CONDUCT ETHICAL RESEARCH? 79

of institutional review boards (IRBs) for human participant research and institutional animal care and use committees (IACUCs) before conduct- ing research. The IRBs and IACUCs are guided by federal regulations and research ethics endorsed by professional societies such as the American Psychological Association, the Association for Psychological Science, and the Society for Neuroscience. IRBs and IACUCs must include at least one member of the community outside the university or agency, avoiding the possibility that inappropriate research might be conducted in secret. Note that these proce- dures currently do not apply to institutions that do not have federal funding, such as private genetics research corporations, although efforts are being made to bring these organizations into compliance with federal standards as well.

As you review the ethical guidelines for both human and animal research participants, keep in mind that the guidelines look much simpler when you read about their provisions than when you try to implement them in the context of real research. This is why the final approval decision lies with a committee as opposed to single individuals.

Human Participants

At the core of ethical standards for human research is the idea that participation is voluntary. No par- ticipant should be coerced into participating.

Although psychologists are well aware that people who volunteer to par- ticipate in research are probably quite different in important ways from those who don’t volunteer, we have chosen to give research ethics a higher priority than our ability to generalize research results.

To ensure that a participant is a willing volunteer, researchers must make provisions for reasonable incentives. Incentives, such as pay or extra credit for participation, must not be so extreme that they become the pri- mary motivation for prospective volunteers. To decide whether to volun- teer for research, a person must have some knowledge of what the research will entail. Researchers must provide prospective participants with an informed consent form, which provides details about the purpose of the study and what types of procedures will occur.

In psychological research, we have the added burden of occasion- ally dealing with participants who are limited in their abilities to provide informed consent due to the very conditions that make them interesting to study in the first place. Developmental psychologists have an obvious interest in children, but a person cannot sign a legal informed consent until age 18. Can you possibly obtain informed consent from a patient with schizophrenia, who suffers from hallucinations and irrational, delusional beliefs? Or from a person in the later stage of Alzheimer’s disease, whose memory and reasoning have deteriorated due to his or her condition? In these cases, legal permission must be obtained from a qualified guardian. The university IRBs play an essential role in evaluating these ethical dilem- mas on a case-by-case basis.

Research should also be conducted in a manner that does no irrevers- ible harm to participants. In some cases, to avoid participants’ desire to appear “normal” and their tendency to try to “outguess” the research,

informed consent Permission obtained from a research participant after risks and benefits of an experimental procedure have been thoroughly explained.

The best scientist is open to experience and begins with romance—the idea that anything is possible. —Ray Bradbury

rticipants is the idea that participation is voluntary. No participant shohoululdd bebe ccoeo rcceded intto o papartrticicipipating.g. oughgh psyychoologissts are well l aaware thatat ppeoplee whwho vovoluuntnteer to parar-- ate in reresearrchch aree ppror bablly y quite diiffefferent iinn immpoporrtanantt wawaysy froom m e whwhoo don’t volulunnteer,r, we haaveve cchohosenn toto ggive reesearrchch eththicicss aa hhighgher iityty tthhan our abililitity y tto generalize research results.

To ensnsuuree thhatat aa pparticipant is a willing volunteer, researchehers must e provvisioons fofor reeaasonable incncentiiveves.s. IInccenentitivves,s, ssucuch h asas ppayy orr exextrtraa t for pparartticipation, must nott bbe soo eextxtrerememe tthhatt ttheyy bbeccomme thhe prri--

y motivation for prospective vovoluluntnteeeersrs. ToTo ddeecidide whwhetheher toto vvoolunn-- for research, a person must have some knowledge of what the research

F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY80

researchers might say they are investigating one factor when they are really interested in another. Most cases of deception are quite mild, as when par- ticipants are told that a study is about memory when it is actually a study of some social behavior. When researchers must deceive their participants, extra care must be taken to debrief participants and answer all their ques- tions following the experiment.

Research using human participants should be rigorously private and confidential. Privacy refers to the participants’ control over the sharing of their personal information with others, and methods for ensuring privacy are usually stated in the informed consent. For example, some studies involve the use of medical records, which participants’ agree to share with the researchers for the purpose of the experiment. Confidentiality refers to the participants’ rights to not have their data revealed to others without their permission. Con- fidentiality is usually maintained by such practices as substituting codes for names and storing data in locked cabinets. Collecting data anonymously, where even the researchers do not know the identity of participants, is the surest way to protect privacy and confidentiality.

Science learns from its past ethical lapses. One of the most egregious examples of unethical research was the Tuskegee syphilis experiment, which lasted from 1932 until 1972. Researchers from the U.S. Public Health Service recruited about 400 impoverished African American men who had contracted syphilis to study the progression

of the disease. None of the men was told he had syphilis, and none was treated, even though penicillin became the standard treatment for syphilis in 1947. Many of the federal regulations discussed in this section were devel- oped in response to this research.

Animal Subjects The topic of using animals in research is guaranteed to stimulate lively, and possibly heated, discussion. Some people are adamantly opposed to animal research of any kind,

While examining the papers of Dr. John Cutler, who led the Tuskegee syphilis study, Wellesley historian Susan Reverby discovered that during the 1940s, U.S. and Guatemalan health officials had deliberately exposed prisoners, soldiers, and mental patients to syphilis and gonorrhea to test the effectiveness of penicillin.

The Tuskegee syphilis experiment, conducted by the U.S. Public Health Service from 1932 to 1972, involved 400 African American men who had contracted syphilis. Failure to treat or inform these participants about their health led to new regulations to prevent such unethical research from being repeated.

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ReRessearrchch uusingg hummanan parartiticicipapantntss shouuldld bbee ririgogororousslyly pprr and confidential. Privacy refers to the participants’ control ove shsharing g of their personal informmatation with others,s, and method enensuriringng pprir vavacycy arere uusuualallyly stattedd inin tthee iinfnfororrmmmed consent exexamplple,e sommee ststuddiies ininvollvee thhe uuse oof mmededical records, w papartrticicippanantts’ agagrereee toto shaarre wwiith h ththee resesearrchcherers s for the purpo the experiment Confidentiality refers to thehe pppaarticipants’ righ

F O S T E R , C E D R I C 1 6 9 2 T S

HOW CAN WE CONDUCT ETHICAL RESEARCH? 81

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whereas others accept the concept of using animals as long as certain con- ditions are met. Currently, about 7 to 8% of published research in psychol- ogy journals involves the use of animals as subjects (American Psychological Association [APA], 2005a). Ninety percent of the animals used are rodents and birds, with 5% or fewer studies involving monkeys and other primates. According to the American Psychological Association (APA), the use of dogs and cats in psychological research is rare.

Research using animals must demonstrate a clear purpose, such as benefiting the health of humans or other animals. In addition to serving a clear purpose, animal research requires excel- lent housing, food, and veterinary care. The most controversial ethical standards relate to minimizing the pain and suf- fering experienced by animal research subjects. The American Psychologi- cal Association provides guidelines for the use of pain, surgery, stress, and deprivation with animal subjects, as well as the termination of an animal’s life. The standards approximate the com- munity standards we would expect from local humane societies tasked with euthaniz- ing animals that are not adopted.

Ethical guidelines for animal research require having a clear purpose for the experiment, providing excellent care for the animals, and minimizing pain and suffering.

Summary 2.3 Principles of Ethical Research

Human participants Animal subjects

No coercion Necessity

Informed consent Excellent food, housing, veterinary care

No harm Minimal pain and suffering

Confidentiality and privacy

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 2 | THE MEASURE OF MIND: METHODS OF PSYCHOLOGY82

Interpersonal Relationships From a Methodological Perspective At the end of Chapter 1, we noted that each chapter would feature a dis- cussion of how the chapter’s material could be used to talk about relation- ships. For this chapter on research methods, we ask whether psychological research methods can be used to differentiate between liking and loving another person.

Using the methods described in this chapter, you can probably think of many different ways to approach this question. You could observe friends and compare their behavior to that of romantic partners. You could con- duct a survey, asking people to rate certain characteristics of people they love versus those of people they like. Perhaps you could correlate physi- ological arousal measures, like pupil diameter or heart rate, with ratings of how much a participant likes or loves another person. Conducting an actual experiment might be a bit tricky, though, both in terms of methods and ethics. How could people possibly be randomly assigned to love and like groups?

A fun example of research in this area was contributed by Andreas Bartels and Semir Zeki (2000). These researchers chose to use correla- tional methods in the form of brain imaging, which we discuss further in our chapter on biological psychology. Brain imaging studies are typically

correlational, because we assume that brain activity in particu- lar areas has a relationship with some ongoing behavior. Once again, it is important to recall that we cannot make conclusions about causality based on correlational data.

Bartels and Zeki’s participants were instructed to supply photographs of people they like and people they love. The pho- tographs were then presented to the participants while their brain activity was observed using functional magnetic resonance imaging, or fMRI. Several differences in brain activity occurred when the participants viewed a lover as opposed to a friend.

Not too surprisingly, areas of the brain associated with reward became more active when viewing lovers than when viewing friends. Areas of the brain associated with social judgment, negative emotions, and assessing the intentions and emotions of other people were less active when viewing lovers than when viewing friends. Love, according to these results, appears to be a combination of reward and less social judgment (see ● Figure 2.20).

The results of this scientific research might help us understand some of our everyday experiences with relationships. Of course, we feel rewarded in the presence of a loved one, and we have to admit that we may miss a flaw or two in someone we love. Friends and family members, whose social judgment has not been silenced, do not miss these flaws and often try in vain to alert us to them.

No amount of experimentation can ever prove me right, but a single experiment can prove me wrong. —Albert Einstein

Bartels and Semir Zeki (2000). These researchers chose to use cor tional mmetethohods in n ththe foormm of brb ain n imimagagini g, wwhihich wwee didiscscuuss ufurtrthh our chchaapter on bioiolologiccal l pspsycychholooggy. BrBraia n imimagagini g sttuddieiess aree tytypip

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F O S T E R , C E D R I C 1 6 9 2 T S

INTERPERSONAL RELATIONSHIPS FROM A METHODOLOGICAL PERSPECTIVE 83

When you view a person you love rather than like:

These areas increase their activity. These areas decrease their activity.

Imaging Love. When people view a photo of a person they say they “love,” brain imaging shows increased activation in reward areas of the brain and decreased activation in areas involved with social judgment.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter Reflections

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Chapter 2 | THE SCIENCE OF MIND: THE DISCIPLINE OF PSYCHOLOGY

We began our discussion of research methods by asking how we know that stuttering is not caused by tickling a baby or leaving it out in the rain. Before reading this chapter, you probably “knew” these ideas weren’t right, but it might have been difficult to say exactly why you felt this way. The brain imaging study demonstrating differences in brain activity

between stutterers and non-stutterers probably looked more convincing to you, but it’s important to give

these types of studies the same scrutiny you would give to the folk myths about stuttering. In other words, practicing critical thinking is important,

regardless of how compelling an argument might seem. This chapter explored the many techniques scientists use to gain knowledge. It should now be much easier for you to identify why you

think the scientific approaches to stuttering are more believable than the folk myths, and you

know exactly how to test the accuracy of any of the explanations for stuttering. Although we pointed

out some of the limitations of these methods, such as the potential artificiality of an experiment, scientists using

multiple methods across the perspectives of psychology have compiled an impressive amount of knowledge about the human mind and the behavior it produces. As you read through the remainder of this textbook, we hope you continue to evaluate the results we present using your best critical thinking skills. <

Our scientific methods and critical thinking provide powerful tools for discovering the real causes of stuttering.

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F O S T E R , C E D R I C 1 6 9 2 T S

KEY TERMS The Language of Psychological Science Be sure you can define these terms and use them correctly. case study, p. 55 confounding variable, p. 64 control group, p. 64 correlation, p. 59 critical thinking, p. 48 cross-sectional study, p. 67 dependent variable, p. 64 descriptive method, p. 55 descriptive statistics, p. 71 double-blind procedure, p. 47 experiment, p. 61 experimental group, p. 64 falsifiable, p. 52 hypothesis, p. 52 independent variable, p. 64

inferential statistics, p. 75 informed consent, p. 79 longitudinal study, p. 68 mean, p. 72 measure, p. 59 median, p. 72 meta-analysis, p. 66 mixed longitudinal design, p. 68 mode, p. 72 naturalistic observation, p. 56 normal distribution, p. 74 objectivity, p. 45 operationalization, p. 66 peer review, p. 53 placebo, p. 47

random assignment, p. 64 reliability, p. 70 replication, p. 53 sample, p. 57 science, p. 45 standard deviation, p. 73 statistical significance, p. 77 survey, p. 57 testable, p. 52 theory, p. 49 third variable, p. 60 validity, p. 70 variability, p. 73 variable, p. 59

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CHAPTER REFLECTIONS 85

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F O S T E R , C E D R I C 1 6 9 2 T S

Environmental factors such as stress, diet, smoking, and exercise, can influence whether a gene is turned on or off.

F O S T E R , C E D R I C 1 6 9 2 T S

The Evolving Mind

Nature and Nurture Intertwined

1 Analyze the role of genes as the building blocks of human “nature,” distinguishing among genotypes, gene expression, and phenotypes.

2 Explain how sexual reproduction increases genetic variation among individuals within a population, even among members of the same family.

3 Assess the importance of heritability estimates and epigenetic analyses in the field of behavioral genetics.

4 Analyze the roles played by mutation, natural selection, migration, and genetic drift as mechanisms of evolution.

5 Articulate the proposal that the human brain is an adaptation, and summarize the evidence supporting this proposal.

6 Evaluate the proposal that altruism is an adaptation, considering the various ways one can benefit by helping another.

7 Explain the mechanisms by which intrasexual and intersexual selection might influence the evolution of human behavior.

8 Explain and illustrate the epigenetic and cultural mechanisms by which nature and nurture can interact to influence human behavior.

Learning Objectives

We all know that identical twins, like the little boys appearing in the inset photo, are, well, identical.

Or are they? For a long time, scientists were puzzled not by the similarities between identical twins, but by their differ- ences. If two people share the same DNA, as identical twins do, why does one get cancer while the other stays healthy? Why does one become obese while the other remains fit?

When science began to unravel some of the mys- teries about genes and how they work, answers to these

questions emerged. You have the same DNA in each cell of

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3 Asseesss the importaance of hheerittababililiityy esstiimam tetes s and epepigigeeneeticc anan lyyseses in tthee fifiel behaviviororalal ggeenetticcss.

4 Analyze the roles played by mutation, natural selection, migration, and genetic dr mechhannisms of evolution.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 3 88

Although they share identical DNA, identical twins become less similar to each other as they age, due to the effects of their different experiences, stress, diet, and habits like smoking on the activity of their DNA. Antonio Nogueira (left) and his identical twin brother Rodrigo (right) both compete in Ultimate Fighting Championship (UFC) bouts, but in different weight classes and with different levels of success. The brothers probably look less similar to each other today than when they were children, reflecting an accumulation of diverse experiences, including injuries.

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When pregnant mice are fed a diet containing BPA, found in plastics, their offspring are more likely to have yellow fur and to be obese.

your body, yet some cells develop into heart cells, others into brain cells, and so on. How does the same set of DNA know how to make these different types of cells? Genes can be turned on and off. The genes that

are not turned off are free to produce the proteins needed to build a particular kind of cell, whether that is a skin cell

or a liver cell. Genes do not just turn on and off as they build a body during development. Your ongoing interactions with the environment can also turn genes on or off. What you eat, whether you smoke or drink, your stress levels, and other environmental factors can influence how your DNA works. Our understanding of these ongoing interactions between genes and the

environment is the reason psychologists no longer argue about the separate contributions of nature and

nurture. In this chapter, we will explore these interac- tions in more detail.

Let’s zoom in to see what’s happening when the environment inter- acts with DNA. You can see a strand of DNA in the large chapter opener image. In mice, a gene called Agouti produces yellow fur and obesity when it is turned on, but brown fur and normal weight when it is turned off (Dolinoy, Huang, & Jirtle, 2007). Certain environmental factors can influence whether the gene is turned on or off. For example, if pregnant mother mice ate food containing bisphenol-A, or BPA, a chemical found in food and beverage containers, baby bottles, dental sealants, and food cans, their babies were more likely to have yellow fur and be obese than were babies of mice that were not fed BPA. The BPA seems to have turned on the Agouti gene (see ● Figure 3.1). How does studying the fur color of mice help us understand the differ- ences between identical human twins? The young twins on the previous

page have a great deal in common, but as they get older, they are more likely to eat different

foods and have different experiences. These environmental influences can change the

way their genes are turned on or off,

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F O S T E R , C E D R I C 1 6 9 2 T S

WHY DO WE SAY NATURE AND NURTURE ARE INTERTWINED? 89

just as the BPA affected the Agouti gene in the mice. These changes accu- mulate over time, so identical twins become less similar as they age.

In this chapter, we will explore how nature and nurture interact with one another to build the mind across the lifespan, but our own personal experience is not the sole influence on our minds. The interaction between nature and nurture has been shaping the human mind over millennia.

Why Do We Say Nature and Nurture Are Intertwined? Along with an understanding of the structures and processes of the brain, which we cover in our upcoming chapter on biological psychology, know- ing how our biological history shapes our behavior is an important part of understanding the mind. In our introductory chapter, we explained how contemporary psychologists view the contributions of nature, our heredity or innate predispositions, and nurture, the results of our experience with the environment, to be closely intertwined as opposed to somehow com- peting with each other for control over behavior.

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nature The contributions of heredity to our physical structure and behaviors.

nurture The contributions of environmental factors and experience to our physical structure and behaviors.

Estimated exposure of a breast-fed human baby from birth to 6 months (an average liter of breast

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Estimated adult exposure

Estimated exposure of a baby from birth to 6 months fed canned formula

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2 Environmental Factors Can Change DNA Activity. BPA, which produced changes in the activity of the Agouti gene in mice, has been found in humans, too. Our exposure (amounts are shown in blue) is similar to the exposure that causes physical and behavioral changes in laboratory animals (shown in red).

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED90

Scholars have not always thought about nature and nurture the way we do today. Instead of viewing the actions of nature and nurture as inseparable, earlier scholars talked in terms of “nature versus nurture” and debated the relative contributions of nature “or” nurture to a particular type of behavior. Credit for describing the contrast between heredity and environment as “nature versus nurture” usually goes to Francis Galton (1869), who was also Charles Darwin’s cousin. Galton believed that intel- ligence was largely the result of inheritance, a topic we tackle in a later

n the introduction to this chapter, you learned about

how a mother mouse’s diet could influence the fur color and weight of her offspring. We, of course, are not mice, so it is fair to ask if this same type of interaction between genes and experience can happen in human beings. The answer to that question is yes. Researchers have known for a long time that victims of bullies often, but not always, develop seri- ous emotional problems later in childhood or adolescence. We also know that having a particular genetic profile involving serotonin, one of the chemical messengers we discuss in the biological psychology chapter, can lead to emotional problems, but again, not in all cases. How can we integrate these findings to learn why some children seem at higher risk than others for developing emotional problems after being victimized by bullies? A good answer to this ques- tion would allow psychologists to tar- get just the right groups of children for treatment. Karen Sugden and her

Genes, Bullying, and Emotional Problems

Connecting to Research

Fifteen-year-old Phoebe Prince of Massachusetts hanged herself after experiencing months of relentless bullying by female classmates. Even after her death, the bullies showed no remorse but continued to mock her on Facebook. Nine were later charged with a variety of criminal offenses, but no legal proceeding will give Phoebe back her life.

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v colleagues tackled this question by studying bullying and a particular type of serotonin gene in 2,232 chil- dren (Sugden et al., 2010).

The Question: Does a particular type of genotype, or individual genetic profile, interact with the experience of bullying to produce a higher risk for emotional problems?

METHODS Over 2,000 children enrolled in the British Environmental Risk (E-Risk) study participated in this analysis. The researchers evaluated the chil- dren’s exposure to bullying during interviews at home when they were 12 years old. Emotional problems were assessed using standard instru- ments, one to be filled out by parents and the other by teachers. Parents and teachers filled out these instru- ments twice, once when the child was 5 years old and a second time when the child was 12 years old. Genetic samples were obtained by swabbing the inside of the children’s mouths, which is also a standard procedure.

RESULTS The serotonin gene studied in this research, the serotonin transporter gene, has a long (L) version and a

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cocolleagues tacacklkleded this ququesestionon bbyy sstuudying bullyying and a partrticicular tyypepe ooff seserototonininn gene in 2,23232 chill-- dren (Sugden et al., 2010).

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F O S T E R , C E D R I C 1 6 9 2 T S

WHY DO WE SAY NATURE AND NURTURE ARE INTERTWINED? 91

chapter on cognition, language, and intelligence. Over the next 150 years or so, many thinkers engaged in a highly spirited debate on this question. As we will see in a later chapter on cognition, contemporary psychologists view intelligence as another example of an outcome shaped by both genetic inheritance and environment.

We can say with some certainty that the “either-or” approach to human behavior has produced some of the most contentious discussions in the history of psychology. Our motive for arguing in favor of the “intertwined” approach to nature and nurture is not intended to sidestep difficult ques- tions, but rather to simply support good science. By zooming out to inte- grate a number of perspectives, both biological and experiential, we reach a more accurate understanding of these questions.

Francis Galton, who was also Charles Darwin’s cousin, was the first to use the phrase “nature versus nurture” in his discussion of intelligence.

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short (S) version, which means that individuals can have one of three genotypes: SS, SL, and LL. These genotypes did not predict emotional problems by themselves, but a his- tory of being victimized by bullies did predict emotional problems.

One of the strengths of this study was its use of a longitudinal design, which we discussed in our chapter on research methods. As you can see in ● Figure 3.2, being bullied not at all or occasionally is not asso- ciated with an increase in emotional problems from age 5 to 12, but being

SS (short/short)

SL (short/long)

LL (long/long)

Bullying victimization None Occasional Frequent

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bullied frequently is associated with an increase in emotional problems, especially for children with the SS genotype. Without this longitudinal design, we might not be able to say whether the behavioral problems among the bullied 12-year-olds were related to genotype or to other pos- sibilities, such as stress at home or a greater likelihood of being victimized due to existing emotional problems.

CONCLUSIONS The results show that being victim- ized by bullies leads to emotional

Interactions Between Genotype and the Experience of Being Bullied. Childhood emotional problems become more common when a child experiences frequent, but not occasional, bullying, especially when the child has the SS genotype for the serotonin transporter gene. Source: Adapted from Sugden et al. (2010).

F i g u r e 3 . 2

problems, but that children with the SS genotype who are bullied fre- quently are more likely than children with either the SL or LL genotype to experience increased emotional prob- lems at age 12. These results shed light onto the question of why some bullied chil- dren appear to be more negatively affected by the experience than others. The results also allow psy- chologists to target specific children for treatment, before the emotional problems at age 12 develop into later problems with mental health.

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED92

Ridley (2003) summarizes the need for an integrated nature-nurture approach as follows:

Genes are not puppet masters or blueprints. Nor are they just the carriers of heredity. They are active during life; they switch each other on and off; they respond to the environment. They may direct the construction of the body and brain in the womb, but then they set about dismantling and rebuilding what they have made almost at once—in response to experience. They are both cause and consequence of our actions. (p. 6)

What Are the Building Blocks of Behavior? Before we can explore the interactions between nature and nurture that contribute to psychological phenomena, like a person’s reactions to being bullied, let’s take a look at the genetic mechanisms that help shape the mind.

Every nucleus in the more than 1 trillion cells of your body, with the exception of your red blood cells and sperm or eggs, contains two complete copies of the human genome, a set of instructions for building a human being. Your personal set of instructions is known as a genotype, which interacts with the environment to produce observable characteristics known as a phenotype. Your genotype might include a gene for blonde hair and another for brown, while your phenotypical, or observable, hair color is light brown.

One copy of your genome was provided by your mother’s egg and the other by your father’s sperm. Each parent contributes a set of 23 chromo- somes, which in turn are composed of many molecules of deoxyribonucleic acid (DNA). Smaller segments of DNA located in particular places on a chromosome are known as genes. Each gene contains instructions for mak- ing a particular type of protein. Gene expression occurs when these genetic instructions are converted into a feature of a living cell. Each cell contains

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genotype An individual’s profile of alleles.

phenotype Observable characteristics. gene Small segment of DNA located in a particular place on a chromosome.

gene expression The process in which genetic instructions are converted into a feature of a living cell.

Twenty-three pairs of chromosomes make up the human genotype.

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WHAT ARE THE BUILDING BLOCKS OF BEHAVIOR? 93

the instructions for an entire human organism, but only a subset of instruc- tions is expressed at any given time and location. Gene expression in a nerve cell is very different from gene expression in a muscle cell or a skin cell.

Different versions of a gene, or alleles, can give rise to different pheno- typical traits. Many alleles can occur for a given gene, but a single individ- ual receives only two, one from each parent. For example, alleles for blood type include A, B, and O, but nobody can have all three. Combinations of your two alleles will make your blood Type A (AA or AO), Type B (BB or BO), Type AB (AB), or Type O (OO). See ● Figure 3.3, which illustrates possible blood type combinations.

If both parents contribute the same type of allele, such as a gene for curly hair, the child would be considered homozygous for that gene (homos means “same” in Greek). If the parents contribute different alleles, such as a gene for curly hair from one parent and a gene for straight hair from the other, the child is heterozygous for that gene (hetero means “different” in Greek). Recessive alleles only determine a phenotype when an individual is homozygous for a particular gene, whereas dominant alleles will determine a phenotype in either the homozygous or heterozygous condition. Because alleles for straight hair are recessive and alleles for curly hair are dominant, the only way an individual can have straight hair is if he or she receives two copies of the straight hair allele, one from each parent. An individual receiving one straight hair allele and one curly hair allele will have curly hair (see ● Figure 3.4).

Whether you have straight or curly hair is a very simple example of how dominant and recessive genes interact, but in many human characteristics, one allele does not entirely dominate another. In the research on bullying we discussed previously, we noted that individuals could have SS, SL, or LL genotypes. Neither the S nor L allele dominates the other. As you can see in ● Figure 3.5, The SL group had levels of emotional disturbance that fell between the extremes of the SS and LL groups (Sugden et al., 2010). If either the S or L alleles were dominant, the SL group would behave just like that dominant group instead.

Genetic Variation

If you have siblings, you are very aware of the fact that having the same biological parents does not guarantee similar appearance, personality, and behavior.

The development of an egg or sperm cell is like shuffling a deck of cards. In both cases, a large number of possible outcomes may occur. When a

Father’s allele

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BO (Type B blood)

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Genotypes and Phenotypes of Blood Type. The three possible blood type alleles—A, B, and O—can be combined to produce Type A, Type B, Type O, or Type AB blood.

F i g u r e 3 . 3

allele One of several different versions of a gene, as in having an A, B, or O blood type allele.

homozygous Having two of the same alleles for a gene.

heterozygous Having two different alleles for a gene.

recessiveness A feature of an allele that will only produce a phenotype in the homozygous condition.

dominance A feature of an allele that will determine a phenotype in either the homozygous or heterozygous condition.

Some genes are characterized by very large numbers of alleles. There are about 500 different alleles for the BRCA1 (Breast Cancer 1) gene, a small number of which are associated with a higher risk for breast and other cancers.

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED94

NA belonging to differ- ent individuals can be

compared using autoradio- graphs. An autoradiograph is formed by labeling DNA fragments with a radioactive marker and then exposing the DNA to X-ray film.

Reading a DNA Fingerprint

Experiencing Psychology

(A, B, C, D)

(E, F, G)

(H, I, J, K)

(L, M, N, O)

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Autoradiograph Results

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In this case, we are looking at a simple paternity test (PBS, 1998). Four DNA samples have been taken from three people: a mother, her child, and the possible father of the child. The two letters for each segment represent the individual’s

genotype. For example, in the first autoradiograph on the next page, the mother is an AD, the child is an AC, and the possible father is a BC.

Use the autoradiographs to com- plete Table 3.1:

Effects of Dominant and Recessive Genes. Curly hair (C) is dominant while straight hair (c) is recessive. The only way a child can have straight hair is to inherit two of the recessive straight hair alleles from its parents. In this example, both parents are heterozygous (Cc) with curly hair.

F i g u r e 3 . 4

Father’s allele

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WHAT ARE THE BUILDING BLOCKS OF BEHAVIOR? 95

SS (short/short)

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Serotonin transporter gene genotype

Some Alleles Do Not Show Dominance. Neither the S nor the L allele of the serotonin transporter gene dominates the other. Among children who have been bullied frequently, those with the SL genotype (shown in green) experience a level of emotional problems midway between that of those with the SS and LL genotypes. If either the S or the L allele was dominant, we would expect the SL group to behave the same way as the homozygous dominant group. Source: Adapted from Sugden et al. (2010).

F i g u r e 3 . 5

parent’s cell divides to make an egg or sperm cell, each resulting cell con- tains 23 chromosomes, one chromosome from each of the parent’s original 23 chromosome pairs. As a result, a single human can produce eggs or sperm with 223 (8,388,608) different combinations of his or her chromosomes. Add this variability to the different possibilities provided by the other parent, and it may seem surprising that we resemble our relatives as much as we do.

Relatedness In spite of this potential variability, we remain very similar to our genetic relatives. We will revisit this

important point later in the chapter when we discuss the evolution of social behavior. Relatedness is defined as the probability that two people share copies of the same allele from a common ancestor. Obviously, if one goes

relatedness The probability that two people share the same allele from a common ancestor.

To evaluate the likelihood of the possible father’s paternity, identify which “letters” the child inherited from its mother and which from its father. The child will receive one allele from each parent, so the child’s com- binations of alleles must be possible

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based on the mother’s and father’s genotypes. For example, if the child had AD in the first column instead of AC, this man would not be the father, as he has neither the A nor the C allele to contribute. Overall, is it possible for this man to have fathered this child?

SOLUTION Keep in mind that genetic tests never “prove” a relationship. They can only disprove one. In our chapter on research methods, we made this same point about all hypotheses. Based on the evidence in this case, we cannot “prove” the hypothesis that this man is in fact the child’s biological par- ent. All we can do is show that he is not the father. If the child had an AD genotype instead of an AC genotype in the first box, as mentioned earlier, this man could not possibly be the father, as he could not supply either the A or D alleles. Such an “exclusion” result is considered absolute evidence of non-paternity. In contrast, the results of this test suggest that it is very likely that this man is the bio- logical parent of the child.

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SOLULUUTITIT OON

F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED96

back in history far enough, we all share common ances- tors. Relatedness, however, is usually computed within a limited number of generations.

The chance that you share an allele with one of your parents is one half, as is the chance that you share an allele with a sibling. First cousins have a one-eighth like- lihood of sharing an allele (see ● Figure 3.6). These types

of calculations led geneticist J. B. S. Haldane to allegedly proclaim, “I would lay down my life for two brothers or eight cousins!” (Con- nelly & Martlew, 1999). Haldane was computing the likelihood that his genes would be passed down to future generations. As we discuss later in the chapter, evolutionary

psychologists suggest that sacrificing yourself for others is much more likely when the “others” are genetically related relatives (see ● Figure 3.7).

Sex Chromosomes

Twenty-two of the 23 pairs of human chromosomes from each parent are perfectly matched. In other words, a gene appearing on one of a pair of chromo-

somes, perhaps a gene for hair color or blood type, will have a correspond- ing gene on its partner. The remaining pair, the X and Y sex chromosomes, does not carry the same genes. Most of the genes located on the Y chromo- some are involved with male fertility. The X chromosome contains genes not duplicated on the Y chromosome that influence a wide variety of char- acteristics, including the clotting of blood and the ability to see the colors red and green.

Genes responsible for hemophilia, or the failure of blood to clot, and red-green colorblindness are found on the X chromosome. These genes are recessive, leading to different outcomes based on the sex of the child receiving the genes. Generally, if a female receives a healthy gene on the X chromosome from one parent and a defective gene on the X chromosome

Given the fact that each parent can pass along over 8 million different combinations of his or her chromosomes, it might be surprising that family resemblance can be so strong, as it is with the Jonas brothers and with mother- daughter actresses Goldie Hawn and Kate Hudson.

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT ARE THE BUILDING BLOCKS OF BEHAVIOR? 97

from her other parent, she will be a carrier for the condition but will not experience it herself. In contrast, a male receiving a defective gene on the X chromosome from his mother will have the condition. Because there is no equivalent gene on the Y chromosome to offset the defective reces- sive gene, it will be expressed. As a result, conditions such as hemophilia and red-green colorblindness are much more frequent among males and are referred to as sex-linked characteristics. Although Queen Victoria of Britain had parents who were not carriers of hemophilia, she, through two of her five daughters (Princess Alice and Princess Beatrice), passed the mutation to various royal houses across the continent. Victoria’s son Prince Leopold, Duke of Albany suffered from the disease. For this reason, hemophilia was once popularly called “the royal disease” (see ● Figure 3.8). You can trace hemophilia, or the royal disease, in Queen Victoria’s family as illustrated in ● Figure 3.9.

Epigenetics Having identical genotypes, as is the case with iden-tical twins, does not guarantee identical pheno- types, or observed characteristics. As we explained in the example of the Agouti gene and the fur color and weight of baby mice, different pheno- types can result from the same genotype due to interactions between the organism and its environment. When factors other than the genotype itself

Genetic relatedness to participant

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Relatedness and Inheritance. People leave more of their estates to those who are more closely related. Direct lineage refers to parents, grandparents, or children of the person making the will, whereas peripheral lineage refers to siblings, aunts, uncles, cousins, nieces, and nephews. A sibling has the same relatedness to an individual as a child (r = .50), but the child is left much more of the estate.

Hemophilia Is a Sex-Linked Trait. If a daughter inherits her mother’s X chromosome containing the allele for hemophilia (XH), she will be a carrier but will not have the disease. If a son inherits this XH chromosome, he will have the disease. Unlike his sister, he does not have a healthy X chromosome to offset the disease allele.

F i g u r e 3 . 7

F i g u r e 3 . 8

XHX Mother

XY Father

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Mario Fraga and his colleagues studied 160 identical twin pairs between the ages of 3 and 74. The two chromosomes on the left belong to 3-year-old twins and those on the right to a pair of 50-year-old twins. Areas of red indicate differences between the two chromosomes related to differences in gene expression. As the twins aged, their gene expression became more different, as indicated by the greater amount of red in the chromosomes from the older twins. Twins who had spent the most time apart showed the greatest epigenetic differences. “Epigenetic differences arise during the lifetime of monozygotic twins,” by Mario Fraga et al., in Proceedings of the National Academy of Sciences 2005 Jul

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genetics Having identical genotypes, as is the case with iden-

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F i g ug ug ug ug u r e 3 . 888

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED98

Queen Victoria (m. Albert of Saxe-Coburg-Gotha)

Alice Leopold Beatrice

lbert of Saxe-Coburg-Got

Victoria Alfred Helena Louise ArthurEdward VII

Grand Duke Louis IV of Hesse

Helena of Waldeck

Victoria Elisabeth Irene (m. Henry of Prussia)

Alix (m. Emperor Nicholas II of Russia)

Frederick Grand Duke Ernest Louis

Henry of Battenberg

Alexander Mountbatten

Victoria Eugenie (m. King Alfonso XIII of Spain)

Maurice Leopold

Alice

Queen Victoria’s mother was not a carrier for hemophilia, and her father did not have the disease. Scientists believe that a mutation occuring in her father’s sperm resulted in Victoria’s being a carrier.

One of Alice’s two sons had hemophilia, and two of her five daughters were carriers. One daughter, Alix, carried hemophilia into the Russian royal family.

Prince Leopold had the royal disease and his daughter Alice was a carrier.

Two of Beatrice’s three sons had the disease. One, Leopold, died during surgery, because hemophilia causes uncontrolled bleeding. Beatrice’s daughter, Victoria Eugenie, married into the Spanish royal family and carried the disease with her.

Hemophilia and European Royalty. Queen Victoria of Great Britain (1819–1901) had nine children. One son (Prince Leopold, Duke of Albany) had hemophilia, and two daughters (Princess Alice and Princess Beatrice) were carriers for the condition. As a result of their marriages to other European royalty, the three children spread the hemophilia gene to the royal families of Germany, Russia, and Spain. For this reason, hemophilia was once popularly called “the royal disease.” Illustration: © Cengage Learning 2013; photos, left to right: © Pictorial Press Ltd/Alamy; Mary Evans Picture Library/CHARLOTTE ZEEPVAT; © Mary Evans Picture Library/The Image Works; Mary Evans Picture Library/

F i g u r e 3 . 9

produce changes in a phenotype, we say that an epigenetic change has occurred. Epi is greek for “over” or “above,” so “epigenetics” refers to the reversible development of traits by factors that determine how the genes perform. The field of epigenetics explores these gene–environment interactions.

Epigenetic change often works by influencing gene expression, the pro- cess by which the DNA forms proteins that contribute to features of living cells. The environment can determine if and when a particular gene is acti- vated. Although many studies in epigenetics examine physical features like fur color, we assume that more complex features of interest to psychologists are also subject to epigenetic influences. In one dramatic example, rats that were licked frequently during infancy by their mothers (the rat equivalent of getting a hug from mom) were calmer than rats licked infrequently when

epigenetics The study of gene– environment interactions in the production of phenotypes.

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WHAT IS THE FIELD OF BEHAVIORAL GENETICS? 99

faced with stress later in life (Champagne, Francis, Mar, & Meaney, 2003). By licking their pups, these mothers had influenced the expression of genes that determined responses to a stress hormone. The nurture provided by the mother had lifelong impact on the offspring’s ability to cope with stress. Children exposed to child abuse have been found to have similar long-last- ing changes in the expression of genes related to stress hormones (Neigh, Gillespie, & Nemeroff, 2009). Happily, these changes appear to be reversible in children who experience consistent and responsive caregiving by foster parents (Fisher, Van Ryzin, & Gunnar, 2011).

Although the application of epigenetics to psychology is quite recent, it is likely that interest in this approach will continue to grow. Epigenetic change provides a clear example of how the human mind responds to the interplay between nature and nurture.

What Is the Field of Behavioral Genetics? The field of behavioral genetics attempts to identify and understand the links between genetics and behavior. These links can help explain individual differences between human beings as well as the differences we see between our species and others.

Although we can say that all human beings share 100% of their genes, we do not share 100% of our alleles, or varia- tions in each gene, giving each of us a unique version of the genome. In other words, we all share genes that produce eye color of some sort, but our different combinations of alleles result in a wide variety of shades. In fact, there are at least 3 million DNA variations in the human genome, enough for us to differ from one another in nearly every gene (Plomin & Spinath, 2004).

Our species also shares quite a few genes with chimpan- zees, mice, fruit flies, yeast, and a weed known as thale cress (see ● Figure 3.10). Behavioral geneticists are less interested in genes we share with other species than in those that make us different from them. For example, recent research points to differences between humans and chimpanzees in a single gene, the FoxP2 gene, that appears to have had a significant effect on distinctly human behaviors, including spoken language (Konopka et al., 2009).

Behavioral geneticists often speak in terms of the heritability of a particular trait, or the statistical likelihood that variations observed across individuals in a population are due to genetics. Heritability is usually pre- sented as a ratio of the amount of variation observed in a population due to genetics relative to the total amount of variation due to both genetic and environmental influences. If genes play no part in producing phenotypical differences between individuals, heritability is zero. For example, genes are responsible for us having hearts, but there is no individual variation

behavioral genetics The scientific field that attempts to identify and understand links between genetics and behavior.

heritability The statistical likelihood that variations observed in a population are due to genetics.

Our species shares genes for eye color, but combinations of alleles produce many different possible shades.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED100

in the population in terms of the presence of a heart—we all have one. Consequently, the heritability of having a heart is 0.0. If genes are totally responsible for all phenotypical differences between individuals, heritabil- ity is 1.0. All variation in the population in terms of having or not having a fatal neurological condition known as Huntington’s disease is entirely due to genetics. If you inherit a Huntington’s gene from one parent, you will develop the condition, so the heritability of Huntington’s is 1.0. Heritabil-

ity of most human traits is typically found between these extremes, in the range of 0.30 to 0.60.

Heritability is a concept that is frequently misunderstood. Heritability always refers to populations, not to individuals. Saying that a trait such as shyness is 40% heritable does not say that 40% of one individual’s shyness is produced by genes and the other 60% by the environment. Instead, a 0.40 heritability ratio suggests that the variations in shyness we see across the population (from very high to very low) are influenced moderately

by both genetic and environmental factors (see ● Figure 3.11). Heritability cannot be assessed without taking the environment into

account, which is another source of potential confusion. If the environment is held constant (everybody is treated exactly the same way), the heritability of a trait will appear to be high. For example, if you plant seeds in trays with identical nutrients, water, and sunlight, the height of the resulting plants will be largely due to their genetic differences. In variable environments, heritability will be lower. If you plant seeds in trays receiving different

The environments provided by adoptive parents, like this mother, are more similar to each other than to the environments provided by biological parents. This environmental similarity can exaggerate genetic influences, a result that must be taken into account when investigating heritability using adopted children.

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Genes Shared With Other Species. Humans share quite a few genes with other species, such as the 18% of genes we share with a weed known as thale cress. However, geneticists are most concerned with the genes that differ from those of other species, like the FoxP2 gene, which appears to be responsible for spoken language. In fact, mutations of this gene cause severe speech and language disorders.

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT IS THE FIELD OF BEHAVIORAL GENETICS? 101

amounts of nutrients, water, and sunlight, the height of the resulting plants will appear to be less influenced by genetics. If you studied the heritability of human intelligence in participants living in extremely wealthy circum- stances, genetic influences would be exaggerated, just as they are when you hold the nutrients, water, and sunlight constant for your plants. Research- ers assessing heritability of human traits attempt to do so within a “typical” range of environments.

Because of these concerns about the influence of environment on herita- bility, some researchers question the use of adoption studies for assessing the relative influences of genetics and environment on child development. These studies compare adopted children to their biological and adoptive parents in an effort to assess the relative impact of heritability. Like our plants with constant amounts of nutrients, water, and sunlight, adoptive families share many common features as a result of the screening process they go through before adopting. Consequently, adoptive parents rarely represent as much diversity as the group of biological parents whose children they adopt. If all adoptive families provide a consistent environment, this factor may inflate the apparent heritability of characteristics examined in the adopted children.

An understanding of heritability can help us evaluate some of the con- tentious arguments in psychology, including issues of group differences in intelligence. Returning once again to our plant example, consider the fol- lowing (Lewontin, 1970). Grab two handfuls of seeds from the same bag and plant each handful in two different trays. One tray has nutrient-rich soil, and the other has nutrient-poor soil. In all other respects (light, water), the seeds receive the same treatment. The plants growing in either tray share an environment, so the differences between the heights of the plants within a single tray are largely due to genetics. However, the fact that the plants in the nutrient-rich tray are taller than those in the nutrient-poor tray is largely the result of environment. In other words, you can have heritability approaching 1.0 within each group and substantial differences in observed traits between groups, and yet have no genetic differences whatsoever between the two groups (which in our example were drawn randomly from the same bag). Knowing that performance on intelligence tests is heritable does not tell us that observed differences between groups of people are due to differences in genetics (see ● Figure 3.12).

Historians will have to face the fact that natural selection determined the evolution of cultures in the same manner as it did that of species. —Konrad Lorenz

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Heritability of Some Human Conditions. Heritability rates tell us how much of the variability seen in a population can be due to genetics. According to these data, we can say that genes have a greater influence on autism than on reading disabilities. Source: Adapted from McGuffin, Riley, and Plomin

(2001).

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED102

Psychology as a Hub Science

Understanding Risk Taking

isk taking is another example of a behavior

that demonstrates an interaction between genetic and

environmental factors. Risk-taking behavior can lead to a number of out- comes that affect society negatively, including risky financial investments, unprotected sex, accidents, violence, substance abuse, gambling, and vic- timization. A better understanding of risk taking provides important insights for many fields, including public health, law enforcement, eco- nomics, and education.

Researchers have reported that risk taking is significantly heritable (Anokhin, Golosheykin, Grant, & Heath, 2009). However, not only does risk taking vary across the lifespan, with adolescents being

notoriously riskier than adults, and between genders (males take more risks than females), but factors such as whether you are a parent, whether you expect to be a parent, your birth order (last-borns are more risky), and how long you expect to live can influence risk-taking behavior (Wang, Kruger, & Wilke, 2009). To give you an idea about how complex risk taking can be, consider the fol- lowing: in 12-year-olds, heritability in both males and females is modest but significant (28% for males; 17% for females), but at the age of 14, heritability rises to 55% in males and

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Comparing Heritability Between Groups. In this demonstration by Lewontin, you can have heritability approaching 1.0 within each group and substantial differences in observed traits between groups, and yet have no genetic differences whatsoever between the two groups (the seeds in each tray were drawn from the same bag). Lewontin was attempting to caution scientists wishing to make heritability conclusions regarding observed racial differences in IQ.

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F O S T E R , C E D R I C 1 6 9 2 T S

WHAT IS THE FIELD OF BEHAVIORAL GENETICS? 103

becomes nonsignificant for females (Anokhin et al., 2009). Again, when we’re discussing heritability, we’re describing the role of genetics in the variations we see across a popula- tion. So in 14-year-old males, genet- ics account for 55% of the variations (high to low) we see in risk taking.

Risk taking is not the type of behavior that lends itself to simple explanations. The genetic perspective featured in this chapter provides con- siderable insight, but if professionals in the fields of public health and edu- cation, for example, want to under- stand the effects of risk taking on rates of unprotected sex or alcohol abuse, a comprehensive exploration of underlying developmental, cogni- tive, social, and clinical factors will be needed.

Risk taking is a complex behavior that demonstrates interactions between genetics and the environment that change over the lifespan. Psychologists can contribute to public health, medicine, and education by providing more insight into this type of behavior.

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Another common misunderstanding of behavioral genetics is the belief that we can identify “a gene for” a particular behavior. For instance, the headline of an article written for the popular website WebMD trumpets “Researchers identify alcoholism gene” (Davis, 2004). It is important to remember that genes encode for proteins, not behaviors. Genes build pro- teins that are used to construct brains, and brains may or may not initiate the behavior of drinking alcohol. Rather than viewing a gene as “causing” a complex behavior, it is much more useful and accurate to view genes as contributing to the development and functioning of the nervous system, which in turn generates observable behavior.

Occasionally, it appears that single genes or a small number of genes may have a disproportionately significant effect on behavior. However, most behavioral differences occur due to interactions between the very small effects of large numbers of genes. As we will discuss in a later chap- ter on psychological disorders, schizophrenia appears to have a moderate genetic basis, but more than 70 different genes have been implicated in the development of the disorder (Mirnics, Middleton, Marquez, Lewis, & Levitt, 2000). Fortunately, methods for analyzing the simultaneous influ- ence of whole sets of genes, as opposed to analyzing one gene at a time, are advancing rapidly. Researchers using these new techniques have identified multiple genes involved with reading disability (Gayan et al., 2005). No one gene can account for reading difficulties, but small differences in clusters of genes can.

mes nonsignificant for females khin et al., 2009). Again, when di i h it bilit ’

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED104

Summary 3.1 Major Concepts in Genetics

Concept Definition Example Genotype An individual’s genetic makeup A person might have a gene for

straight hair and a gene for curly hair.

Phenotype An individual’s observable trait A person has curly hair.

Gene

A sequence of DNA in a specific location on a chromosome that contains the instructions for making a protein.

The serotonin transporter gene is located on chromosome 17.

Gene expression Information from a gene is used to produce a protein.

Maternal diet in mice can affect the expression of the Agouti gene.

Allele Father’s allele

Mother’s allele A

AA (Type A blood)

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AO (Type A blood)

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B O

One of two or more possible variations of a gene

Blood type alleles can be A, B, or O.

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Having two of the same alleles Having the SS or LL forms of the serotonin transporter gene

Heterozygous Having two different alleles Having the SL form of the serotonin transporter gene

Dominant An allele that is expressed regardless of whether it is homozygous or heterozygous

The allele for curly hair is dominant.

Recessive An allele that is expressed only when it is homozygous

The allele for straight hair is recessive.

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F O S T E R , C E D R I C 1 6 9 2 T S

HOW DOES EVOLUTION OCCUR? 105

How Does Evolution Occur? The human genome is the product of millions of years of evolution, defined by modern biologists as “descent with modification from a common ances- tor.” The study of evolution allows us to trace the family tree of living things.

In his book The Origin of Species, Charles Darwin proposed that species evolve or change from one form to the next in an orderly manner (Darwin, 1859). Darwin was well aware of the procedures used by farmers to develop animals and plants with desirable traits by mating particular individuals to each other. A farmer’s goal to raise the strongest oxen for pulling a plow might be accomplished by breeding the strongest available oxen to each other. In these cases, the farmer is making the determination of which individuals have the opportunity to produce offspring. Darwin suggested that instead of a farmer choosing which animals would breed and pass their genes along, the pressures of survival and reproduction in the wild would make the choice, a process he named natural selection. Organisms that survive long enough to reproduce would pass their traits along to the next generation. Organisms that did not reproduce would not have the oppor- tunity to pass their traits along to future generations. As geneticists often remind us, we have no infertile ancestors.

In the more than 150 years since The Origin of Species was first pub- lished, our understanding of genetics and the fossil record has expanded exponentially, lending substantial further support for Darwin’s views. Surprisingly, Darwin was able to derive his theory without the benefit of a basic understanding of genetics. He was unable to account for the varia- tions he observed in a particular trait. That understanding was provided by Gregor Mendel (1822–1884), who discovered ways to outline and predict the inheritance of particular traits, like the color of flowers, in his research on pea plants (Mendel, 1866). Mendel, in turn, was working without our modern understanding of genes and chromosomes. Combining current understanding of genetics with the natural selection processes proposed by Darwin provides scientists with powerful hypotheses about the progres- sion of species over time.

Charles Darwin’s Theory of Evolution described how species change in an orderly manner.

Darwin understood that breeders could influence the traits of offspring by mating particular individuals. He believed that natural selection operated according to the same principles. The pressures of survival and reproduction in the wild would take the role of the breeder—determining which traits are passed along to the next generation.

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evolution Descent with modification from a common ancestor.

natural selection The process by which survival and reproduction pressures act to change the frequency of alleles in subsequent generations.

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F O S T E R , C E D R I C 1 6 9 2 T S

Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED106

Mechanisms of Evolution

In addition to the process of natural selection described by Darwin, evolution can result from mutation, migration, and genetic drift.

Mutations are errors that occur when DNA is replicated. The average human baby is born with about 130 new mutations, but the vast majority have no effect (Zimmer, 2009). Mutant alleles that provide some advantage often spread through the population, but most mutant alleles that result in a disadvantage disappear from future generations. Migration occurs when organisms move from one geographical location to the next. Pheno- typical traits that are advantageous in one environment might be less so in another. Genetic drift produces change from one generation to the next through chance or accident. Type B blood is virtually absent in contempo- rary populations of Native Americans, most likely due to chance (Halver- son & Bolnick, 2008). The handful of ancestors crossing the Bering Strait 10,000 years ago appears to have included no individuals with the Type B allele. If the blood type alleles of the ancestors had been more representa- tive of the entire human population, more of their descendants would have Type B blood.

We can demonstrate the effects of evolutionary processes—mutation, migration, genetic drift, and natural selection—on the history of one allele: the recessive allele for blonde hair. The original appearance of the allele for blonde hair was probably the result of a random mutation that occurred in Northern Europe some 10,000 years ago (Frost, 2006). Migration, or rather the lack of it, might account for the relatively restricted area in Northern Europe populated by blondes until fairly recent times. Geographical barri- ers of mountain and ocean contained the allele for many centuries. Genetic drift, or changes in the genome due to chance or accident, undoubtedly reduced the global frequency of the blonde allele between 1300 and 1700, as waves of Bubonic plague decimated the European population, which at that time contained nearly everyone carrying the blonde allele. If by chance every single person carrying the blonde allele had died from the plague before reproducing, the allele would have disappeared from the human genome (see ● Figure 3.13 ).

Has natural selection influenced the blonde gene? Some anthropolo- gists and biologists believe it has. When a person has a choice of mates of equal value, he or she will select the one that “stands out from the crowd” (Frost, 2006). Individuals with blonde hair color, which was different and more rare, might have enjoyed more reproductive success than those with more common, darker hair col- ors. It is interesting to note that in Germany, with its high percentage of blondes, the trait of blondness is viewed differently than in other countries where blondes are rela- tively rare. German men report that they would marry a blonde because she is likely to be a good home- maker, but they find women with dark hair more sexually attractive.

Gregor Mendel (1822–1884) made important discoveries about inheritance at about the same time that Charles Darwin was working on his theory of evolution, but neither scientist was aware of the work of the other, nor did they know about genes and chromosomes. Modern geneticists combine this knowledge to form powerful hypotheses about the nature of living things.

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F O S T E R , C E D R I C 1 6 9 2 T S

HOW DOES EVOLUTION OCCUR? 107

This finding supports the idea that rare things tend to be viewed as valuable (in this case, attractive; Bem, 2001).

Any consideration of evolution must include the question of what exactly natural selection selects. Natural selection favors the organism with the highest degree of fitness, defined as the ability of one genotype to reproduce relative to other genotypes. The concept of fitness includes survival to adulthood, ability to find a mate, and reproduction. Fitness is not some static characteristic, such as being strongest or fastest. Instead, fitness describes the interaction between characteristics and the environ- ment in which they exist. A genotype that succeeds during the Ice Age may be at a significant disadvantage during periods of global warming. Animals in very cold climates tend to have short legs and stocky bodies, which help retain heat, whereas animals in very warm climates have long legs and slim bodies, which release heat. Once again, we see the need to consider nature within the context of nurture.

Adaptation Adaptation can refer to either the process or the result of change due to natural selection. In other words, a species can respond to an environmental change by adapting, and

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adaptation A change due to natural selection.

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED108

features of the new phenotype may be referred to as adaptations. Adapta- tions can take many forms. Adaptations can be behaviors, such as jumping higher to better avoid a predator, or anatomical features, such as eyes that can see color. Adaptations do not necessarily produce perfection. Any adaptation that is “good enough” to contribute to the fitness of an organism will carry forward into future generations.

A classic example of very rapid adaptation is the case of the English peppered moth Biston betularia. Prior to the Industrial Revolution, the majority of peppered moths found in England were a light gray color, which allowed them to hide against the similar colors of tree bark. Darker moths did occasionally appear beginning in about 1848, but as they were less capable of hiding from predators, they made up only about 1% of the population. With increasing industrialization, tree bark became frequently coated in soot. The once-camouflaged light gray moths now became an easy target for predators against the darker background of the sooty trees. Very rapidly, the darker moths became the norm, reaching frequencies

of about 98%. As pollution came under better control, tree bark returned to its original light gray color, and the lighter moths once again became the norm. The peppered moth population success- fully adapted to changing environmental circumstances, with color playing the role of an adaptation. The moths did not “decide” to change color. Natural selection, in the form of greater rates of reproductive success on the part of moths with a particular color, changed the frequencies of color genes within the population.

Adaptations often appear to be compromises between costs and benefits. Adult human males have about 10 times as much tes- tosterone as adult human females. Testosterone conveys a repro-

ductive advantage, as men with higher testosterone report having more sex partners and earlier age at intercourse (Lassek & Gaulin, 2009). On the negative side, however, high testosterone levels are correlated with lower immune system functioning, making the high testosterone males more vulnerable to disease.

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The dark and light coloring of the peppered moth population in Great Britain changed in response to pollution from soot that collected on trees and changed again when pollution controls reduced the soot.

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F O S T E R , C E D R I C 1 6 9 2 T S

HOW DOES EVOLUTION OCCUR? 109

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Males with high testosterone report more chances to reproduce, but testosterone also lowers the response of the immune system. Extremely high levels of testosterone, due to the use of performance enhancing drugs, might be contributing to the early deaths of some professional wrestlers, like Curt Hennig.

Adaptation is only one source of evolutionary change. Random events, such as the collision of meteors with Earth and resulting climate changes, are believed to have destroyed some types of life and provided broad oppor- tunities for others. We are also limited in our ability to use adaptation to predict the future. The study of evolution is similar to the study of history. Although we gain insight into wars by studying the causes of World War II, we cannot use our knowledge to predict future wars with any precision. We can be fairly certain that antibiotic-resistant bacteria, global warming, pol- lution, and reproductive technologies are probably changing the face of the human population as this text goes to press, but where all these changes will lead us remains unknown.

Evolution of the Human Brain

Our interest as psychologists is in the mind, and the mind and the behavior it produces originate in the structures and processes of

the brain and nervous system. A nervous system is a relatively recent invention in the history of life, and one that is enjoyed only by animals. Our species, Homo sapiens, which features an espe- cially advanced brain, appeared somewhere between 100,000 and 200,000 years ago.

Anthropologists use the term hominin to describe species that walked on two feet, had large brains, and are assumed to be related to modern humans. Over the 7-million-year period of hominin evolution, brains grew very rapidly, suggesting that improved intelligence was quickly translated into substantial advantages in survival. Early tool-using hominins, the australopithecines, had brains that were about the same size as those of modern chimpanzees, or about 400 cubic cm. Homo erectus, a hominin living about 1.5 million years ago, had a brain of about 700 cubic cm, and the brains of modern humans, or Homo sapiens, are about 1,400 cubic cm.

Hominins were not the only creatures who evolved very large brains and considerable intelligence. The other primates, elephants, and whales are not lacking in these areas. Although the challenges of finding food,

Early hominins, like the one on the left, had brains that were about the same size as those of chimpanzees. Very quickly, however, brain size doubled by the time our own species, the modern Homo sapiens shown on the right, appeared sometime between 100,000 and 200,000 years ago.

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Hominins were not the only creatures who evolved very large brains

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED110

avoiding predators, and navigating through territories require considerable intelligence, these ecological challenges are no match for the complexity of social life faced by the hominins. The major factor distinguishing human intelligence from the intelligence of other species is the richness and com- plexity of the social behavior supported by the human brain. Managing the abilities to distinguish friend and foe, imitate the behavior of others, use language to communicate, recognize and anticipate the emotions, thoughts, and behavior of others, maintain relationships, and cooperate required the evolution of a special brain indeed (Cacioppo et al., 2002; Hrdy, 2005; Roth & Dicke, 2005). Comparisons of the challenges faced by different species support a stronger role for social complexity than for ecological complexity in building bigger brains (Dunbar & Schultz, 2007).

The Contemporary Human Brain

You surf the Internet, complete your calculus home- work, and read this textbook with a brain that is essentially the same size as that of your very early Homo sapiens ancestors, who first appeared some-

where between 100,000 and 200,000 years ago. Although we can understand the advantages of big, intelligent brains to

survival, we do not know why advances such as agriculture, literacy, and urbanization have not been accompanied by additional increases in brain size. It is possible that we have reached an equilibrium between our needs for intelligence and the costs of a big brain. Brains are very expensive to run in terms of nutrients. Although the brain comprises only about 2% of the body’s weight, it requires about 15% of the body’s resources when at rest. In addition, brain size may be limited by the dimensions of the birth canal. Further change may not occur unless we experience a drop in the costs of big brains, a change in nutrients, or additional pressures for greater intelligence.

The fact that brain size has not changed much during Homo sapi- ens’ time on Earth does not imply that the evolution of the human brain has ended or that average intelligence has remained the same. Modern genetic techniques allow researchers to “date” changes in a particular gene. Genes involved with brain development appear to have changed as recently as 6,000 years ago (Evans et al., 2004; Evans et al., 2005). As we discuss in a later chapter on cognition, IQ test scores have increased dramatically worldwide over the last 100 years (Flynn, 1999). If brain size has not changed for 100,000 years, let alone during the last 100, how can we account for the observed increase in intellectual performance? It is likely that environmental factors, including nutrition and education, might account for the improvement.

It is somewhat surprising that innovations such as agriculture and transportation are not associated with further increases in human brain size. Photos, left to right: © Stephen Coburn/

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HOW DOES EVOLUTION OCCUR? 111

Summary 3.2 Principles of Evolution

Concept Definition Example Natural selection A trait’s frequency in a population

is determined by the survival and reproductive success of the organisms with the trait.

Faster rabbits are more likely to survive and reproduce than slow rabbits, leading to more fast rabbits in subsequent generations.

Mutation Genetic changes that occur spontaneously or due to external factors like radiation

A mutation about 10,000 years ago led to the appearance of blonde hair.

Migration Populations move from one area to another.

Moving from a cold to a warm climate might change the natural selection of traits in a species.

Genetic drift Chance events influence the frequency of alleles.

Huntington’s disease is much more common than usual among the Afrikaner population of South Africa, because a carrier was among the small number of Dutch immigrants to survive.

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The recessive sickle-cell trait has low fitness in general because it can produce disease, but because the trait protects the individual from malaria, it has higher fitness in populations living where malaria is common.

Adaptation

Evolutionary changes whereby a population becomes better suited to its environment

The moth population changed from primarily light colors to dark colors when the trees they inhabited became darker due to pollution.

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED112

How Does Evolution Influence Behavior? We mentioned in an earlier section that behavior can be adaptive. If an animal that is good at hiding in the bushes is more successful than others of its species in escaping predators, it is likely that the ability to hide will spread through subsequent generations of the population.

Behavior like hiding, however, is unlike the other adaptations we have discussed so far, such as the color of a moth or blonde hair. Color is a physical characteristic, and it is a fairly simple matter to identify the genes

associated with these phenotypes. Behavior as a phenotype is considerably more complex. Behavior is not an anatomical structure like a wing or an eye. Can we assume that behavior is shaped by the same evolutionary forces that affect physical traits? Charles Darwin certainly thought so. In his Descent of Man, Darwin writes:

The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind. We have seen that the senses and intuitions, the various emotions and faculties, such as love, memory, attention, curiosity, imitation, reason, etc., of which man boasts, may be found in an incipient, or even sometimes in a well-developed condition in lower animals. (1871, p. 126)

The Evolutionary Psychology Perspective

Among the psychological specialties we discussed in our introductory chapter, evolutionary psychol- ogy is the most relevant to our current discussion of the evolution of behavior. This approach to the

mind assumes that our current behavior exists in its present form because it provided some advantage in survival and reproduction to our ancestors (Cosmides & Tooby, 1997).

The evolutionary psychology approach not only owes an obvious debt to Charles Darwin but is also a direct descendant of the functionalism sup- ported by William James. As the term functionalism implies, behavior is seen as promoting survival, as opposed to being random and pointless. The goal of evolutionary psychology is to explain how the patterns of behavior we share with other human beings have been shaped by evolution.

Origins of Social Behavior

Reconstructing the evolution of the nervous system is difficult and tracing the origins of individual behavior is even more challenging, but identifying

the roots of social behavior might be the most difficult task of all. Occa- sionally, physical evidence has allowed scientists to determine whether

Physical features, like the coloring of an animal that allows it to hide, are well-understood types of adaptations. Evolutionary psychologists attempt to explain how behaviors can be adaptive, too.

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HOW DOES EVOLUTION INFLUENCE BEHAVIOR? 113

dinosaur parents stayed around to look after their young, but such accounts leave much detail unexplored and unexplained.

A number of factors are believed to influence the social behavior of any particular species, including mating systems, the availability of resources such as food, water, and shelter, the exposure to predators, and competi- tion. We will see how these factors might have shaped the unique social lives of early humans.

Humans as a Social Species In spite of our admi- ration of the rugged individualist, one of the out- standing features of human beings is our rich and essential social nature, which we explore in more detail in our chapter on social psychology. To understand the evolution of social behavior, we need to explore its advantages for survival and reproduction.

In typical environments, individual animals are likely to come into contact with others, leading to a variety of possible interactions and outcomes. In each case, shown in Table 3.2, Individuals either benefit or not from the interaction, ultimately affecting their survival and reproductive success. Both parties benefit equally if they cooperate. For example, two hunters can work together to bring down an animal that neither could successfully hunt alone. Sharing the resulting meat with the families of both hunt- ers would contribute to their survival and reproductive success. Much social behavior probably originated in these types of situations, where the benefits of cooperation for an individual’s survival and reproduction out- weighed any disadvantages of cooperating.

Cooperation, however, is not the only way two individuals can interact. One person could steal food from another, allowing the thief ’s family to survive while the victim’s family starves to death. In still other interactions, both participants lose. In some divorce proceedings, the partners are so determined to keep each other from maintaining resources that everything goes to the attorneys. In these cases, the reproductive success of both would be in danger. Finally, in altruism, one individual sacrifices himself or herself to benefit another individual.

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED114

Altruism is widespread in the animal kingdom. Most of us have expe- rienced a honeybee sting, which is suicidal behavior on the part of the bee in an effort to protect its hive (Wilson, 1975). As we will discuss in greater detail in a later chapter on social psychology, altruism is one of the most challenging social behaviors to explain in evolutionary terms. Charles Darwin himself was puzzled by the apparent sacrifice of some individuals that led to the survival of the group. If altruism results in the destruction of the individual with altruistic genes, why doesn’t this behavior disappear? To explain this phenomenon, we return to the concept of relatedness pre- sented earlier in the chapter. Sacrificing your life to save a close blood rela- tive might actually increase the likelihood that your alleles would be passed along to subsequent generations.

At this point, you are probably thinking that you often behave altruistically with people who are not at all related to you. You

might have stayed to comfort a friend who just experienced a death in the family, even though you flunked your mid- term the next day as a result. How can we explain these

behaviors, which are known as reciprocal altruism (Trivers & Burt, 1999)? In cases of reciprocal altru-

ism, it is customary to help another individual when you can reasonably expect the other individual to

return the favor at some future date. Reciprocal altruism is likely to flourish in situations where individuals are in regular contact with one another. As we will see in a later chapter on social psychology, reciprocal altruism also requires the ability to recognize and remember cheaters.

Altruism can extend to entire social organizations, regardless of the degree of relatedness (Chicago Social Brain Network, 2011). Among the Emperor penguin (Aptenodytes forsteri), survival of the chicks in the hostile Antarctic cold depends not only on an individual parent but on the larger huddle formed by other parents. Human survival similarly depends on

Altruism, or the sacrifice of yourself for others, is more common among related individuals, but it also occurs when we are in close social contact with others. Honeybees sting to defend their hive, but in doing so, end their own lives.

Cooperation allows human beings to carry out complex behaviors that would be impossible for a single individual to perform successfully.

reciprocal altruism Help you provide another person when you expect the person to return the favor in the future.

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HOW DOES EVOLUTION INFLUENCE BEHAVIOR? 115

Genghis Khan may have been the most prolific human male in history. His distinctive Y chromosome has been identified in 16 million living men, or 0.5% of the world’s current total.

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col lective abilities, rather than individual success. It might sound counter- intuitive, but our altruism might have its roots in the warfare conducted by our hunter-gatherer ancestors (Bowles, 2009). As Darwin observed:

A tribe including many members who, from possessing in a high degree the spirit of patriotism, fidelity, obedience, courage, and sympathy, were always ready to aid one another, and to sacrifice themselves for the common good would be victorious over most other tribes; and this would be natural selection. (1871, p. 166) For a gene to survive in subsequent generations, the individual carry-

ing the gene must not only survive, but his or her children must survive to reproduce as well. Because of our long period of dependency in child- hood, along with our rather puny fighting equipment in the form of teeth or claws, we humans are especially in need of our social structures for survival. To the extent that genes build structures consistent with social tendencies, they are more likely to survive into future generations.

Sexual Selection Sexual selection was Darwin’s term for the devel-opment of traits that help an individual compete for mates (Darwin, 1871). To what extent is human behavior influenced by sexual selection?

Parental Investment Sexual selection is influenced by the different invest- ments in parenting made by males and females (Emlen & Oring, 1977). In many species, including our own, the female bears the majority of the costs of reproduction, from the carrying of the developing organism until birth to the nurturance of the young until adulthood. As a result, human females face much sharper limitations than human males on the number of children they can produce in a lifetime. If the goal is to pass your genes along to subsequent generations, and you are only going to produce one or two children, each child had better be as healthy and well nurtured as possible. The average number of children per woman worldwide dropped dramati- cally between 1950 and 2005 (United Nations, 2009). Between 1950 and 1955, the number of children per woman was 3.45 in the United States, 5.91 in India, and 6.11 in China. Between 2000 and 2005, those numbers dropped to 2.04, 3.11, and 1.77, respec- tively (see ● Figure 3.14 ). In contrast, Genghis Khan may have been the most prolific human male in his- tory. His distinctive Y chromosome has been identi- fied in 16 million living men, or 0.5% of the world’s current total (Zerjal et al., 2003).

Although Genghis Khan’s success in passing his genes to future generations may suggest that the best reproductive strategy for males would be promiscuity, this is not usually the case. In species such as our own, with lengthy and complex development leading to adulthood, a

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED116

male that abandons his offspring puts their survival at risk (Gibson, 2008). Even if a man fathers many children, his genes are less likely to make it into the next generation if most or all perish from lack of care.

The mother can maximize her children’s chances of survival by choos- ing a father who will not only pass along healthy genes but will participate in the raising of children. Women have the ability to make very accurate

predictions of a man’s interest in children, simply by looking at a photograph of his face (Roney, Hanson, Durante, & Mae- stripieri, 2006). Men with facial features correlated with high testosterone (strong brow ridge, square chin—the Arnold Schwarzenegger look) are viewed as less likely to participate in childrearing than are men with facial features correlated with lower testosterone (a Tom Hanks or Leonardo DiCaprio look). These results suggest that women would be able to determine a man’s potential as a father before any reproduc- tive investment occurs.

Traits Possibly Influenced by Sexual Selection Earlier in this chapter, we discussed how blonde hair might have provided a reproductive advantage, because its relative novelty made it an attractive feature. What other types of human traits appear to fit Darwin’s ideas about sexual selection?

Sexual selection might occur in two ways. In intrasexual selection (intra means “within”), members of one sex com- pete with each other for access to the other sex. In some species, such as deer, males engage in fights that determine which males are able to mate and which are not. Features like large antlers that assist in winning a fight could become sexually selected. In intersexual selection (inter means “between”), characteristics of one sex that attract the other might become sexually selected.

Evolutionary psychologists have argued that a number of human traits might have been subjected to sexual selection, including humor (discussed in an upcoming Thinking Scientifically feature) and vocabulary. Accord- ing to this argument, human males use humor and their vocabularies to impress females with their intelligence due to intersexual selection. In romantic situations, males use more uncommon, fancy words than they do in other situations (Rosenberg & Tunney, 2008). We can also tell you about one behavior that does not successfully attract females—taking unneces- sary risks (Wilke, Hutchinson, Todd, & Kruger, 2006). However, risky activities might have more positive outcomes for competition between males than for attracting females.

Culture Not only are human societies directly influenced by our biological history, but they also bear the stamp of the inventions of the biological brain in the form of culture. Cultures provide practices, values, and goals that can be shared by groups of people. Human cultures arise from knowledge that is transmitted socially. Lan-

Women show the ability to predict a man’s score on the Infant Interest Questionnaire, which might indicate how involved a father he would be, by detecting the influence of testosterone on his facial features. The face at the top indicates high testosterone, while the one at the bottom indicates low testosterone.

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it an attractive feature. What other types of human t apppepearar to fitfit Darwiw n’s idideaeas s aba out t ssexual sselelecectition??

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F O S T E R , C E D R I C 1 6 9 2 T S

HOW DOES EVOLUTION INFLUENCE BEHAVIOR? 117

guages, morality, arts, laws, and customs make up a diverse and vibrant part of human social interactions.

Experiences shaped by culture, like other types of experience, interact with survival and reproductive pressures. How might cultural differences have impacted our ancestors’ survival? We can gain insight into our spe- cies’ cultural history by observing contemporary preagricultural societ- ies, such as the Waorani and Yanomamö of the Amazonian Basin. These groups are remarkably warlike. Fights between villages account for 30% of the deaths among Yanomamö males (Chagnon, 1988) and 54% of deaths among Waorani males (Beckerman et al., 2009). These observations sug- gest that aggression was probably an important part of our ancient past, but we cannot assume this behavior is strictly biological. Instead, cultural traditions in the two groups have led to very different patterns of reproduc- tive success. Aggressive Yanomamö men produce more children than less aggressive Yanomamö, but less aggressive Waorani men have more surviv- ing offspring than aggressive Waorani (Beckerman et al., 2009). A simple cultural distinction—the Yanomamö practice of standing down between raids, which was not a practice shared by the Waorani—appears to account for the differences observed in the impact of aggression on reproductive success.

Our social minds were shaped by the cultures of hunter-gatherer groups until the development of agriculture approximately 10,000 years ago. With improved control of the food supply, less geographical mobility, and larger communities, human beings entered a new era of social inter- action. Although we believe that many features found in modern human behavior, such as reciprocal altruism, originated in the hunter-gatherer society, further social adjustments were required as groups became larger and more complex.

The Waorani (left) and Yanomamö (right) of the Amazon basin share very high rates of aggression, yet experience different reproductive outcomes. Reproductive success is higher among the most aggressive Yanomamö and the least aggressive Waorani. A simple cultural distinction—the Yanomamö practice of standing down between raids, which was not a practice shared by the Waorani—appears to account for the differences observed in the impact of aggression on reproductive success.

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED118

Agriculture, with its emphasis on land ownership, might have been the origin of patriarchal systems, in which men maintain control of resources, and inheritances follow the male line. Unlike hunter-gatherer societies, which are relatively egalitarian as far as the rights of men and women go, agricultural societies tilted the control of food and impor- tant resources in favor of men. Early industrialization merely built upon agricultural systems and, if possible, accentuated the power differential between males and females. More contemporary trends are once again moving in a more egalitarian direction, with women in industrialized countries enjoying considerable financial independence and reproductive choice. These changes will no doubt have further effects on our social environment.

As societies became larger, human beings took advantage of their large brains to devise new cultural systems to maintain group cohesion. Emerging societies shared many of the same types of internal conflict, so we typically find similar moral, religious, and legal systems across diverse cultures that attempt to control marriage, “character” issues such as honesty, and the transfer of precious resources.

ow often have you found yourself roaring with laugh- ter at something the people

around you don’t find remotely funny? What roles does sexual selection play in a person’s sense of humor?

When pairs of female identical or fraternal twins rated various cartoons by Gary Larson (The Far Side) on a scale of 0 (a dud) to 10 (the funniest thing you have ever seen), the degree of the women’s genetic relatedness did not predict their reaction to the cartoons (Cherkas, Hochberg, Mac- Gregor, Snieder, & Spector, 2000).

Unlike many studies that show

greater similarities between identi- cal than fraternal twins, agreement about what is funny was just as likely among the fraternal twins as among the identical twins. According to the researchers, environmental influ- ences, such as peer attitudes and exposure to “Dad’s humor,” may have dominated the development of each woman’s sense of humor.

Although the twins did not show a strong influence of nature in their preferences for humor, this find- ing does not mean that a sense of humor is purely a result of environ- mental factors. Significant evidence

points to a very important role for humor in human mate selection. When men and women describe an “ideal date,” both sexes indicate that a sense of humor is an important feature, but there is a significant dif- ference in what they mean by that term (Bressler & Balshine, 2006). Men were interested in women who appreciated, rather than produced, humor, while women were inter- ested in men who made them laugh. Women appear to signal their inter- est in a man by laughing frequently, whereas the frequency of men’s

The Sexual Selection of Humor

Thinking Scientifically

The changes that accompanied the move from hunter-gatherer to farmer shaped human culture.

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HOW DOES EVOLUTION INFLUENCE BEHAVIOR? 119

With all the flaws of our groups, whether we’re looking at families, communities, or nations, we retain a strong need to belong. As we will see on many occasions in this textbook, human beings do not thrive in isolation. Our dependence on kinship, friendship, and group membership, honed over the course of 100,000 years or more of social living, continues to influence our behavior today.

Human beings have developed a strong need to belong, and develop traditions that enhance a sense of group membership.

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laughter appears to be unrelated to their judgment of a woman’s attrac- tiveness. Further support for humor’s role in mate selection comes from the observation that men and women do not seem to care as much about a sense of humor when selecting a friend as opposed to a lover.

What advantages might a good sense of humor provide that could make it a subject of sexual selec- tion? Producing a good joke requires sophisticated cognitive skills, creativ- ity, and the ability to see situations from more than one point of view, qualities that signal the good intellec- tual and social functioning preferred by females.

According to evolutionary psychologists, humor might be used by humans to attract mates, because humor indicates intelligence.©

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED120

Summary 3.3 Evolutionary Influences on Behavior

Concept Definition Example Cooperation Working together to benefit all

parties involved Hunters working together to kill an animal that individual hunters could not kill on their own

Altruism Sacrificing yourself to save another A young mother threw herself over her infant during a parking lot shootout. She died, but the infant survived.

Reciprocal altruism Sacrificing when you expect the recipient might do the same for you at some future time

Sharing food with a hungry person thinking that someone might share with you later on

Sexual selection

The evolutionary pressure on traits that help individuals find mates

Women may choose men whose facial appearance is correlated with being a good father.

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INTERPERSONAL RELATIONSHIPS FROM AN EVOLUTIONARY PERSPECTIVE 121

Interpersonal Relationships From an Evolutionary Perspective This chapter emphasized how the human mind has been shaped by its his- tory. Because of the critical role our social behavior played in our species’ survival over many thousands of years, it should come as no surprise that the evolutionary perspective has so much to say about important human relationships. However, in its functionality, this evolutionary approach is rarely very romantic.

In our chapter on social psychology, we will argue that “birds of a feather” really do flock together, in that perceived similarities are important to many relationships. We like to believe that our choice of mate is based on factors like physical attractiveness and mutual interests and values. The evolutionary approach, however, suggests that another type of compatibility is important for romantic relationships—a compatibility of genes that contribute to the immune system.

A cluster of genes known as the major histocompatibility complex (MHC) appears to be subject to sexual selection (Wedekind & Füri, 1997). As described in this chapter, this type of sexual selection operates on traits in one sex that influence the choices by the other. A child with a heterozy- gous set of MHC genes is better prepared to battle infec- tions than is a child with MHC genes that are similar to one another. As a result, our children are more likely to survive if we select a mate that has a different set of MHC genes than we do.

Short of asking potential mates to undergo DNA testing, how are we supposed to accomplish this? Apparently, we do have a method that might have directed the mating choices of our ancestors. Different configurations of the MHC genes produce distinctive body odors that are easily detected and distinguished from one another. When men and women were asked to rate the pleasantness of the odors of T-shirts that had been worn by two women and four men, they pre- ferred smells associated with MHC genotypes that were dif- ferent from their own. Participants noted that the more “pleasant-smelling” T-shirts often reminded them of an ex. Gender did not play a role—smell preference was not influenced by whether the T-shirt wearer had been of the same or the opposite sex as the perceiver.

We do not want to suggest that this MHC gene cluster is the primary criterion we use for choosing partners, but it does remind us that some of our behavioral tendencies have deep roots in our species’ history.

Although “birds of a feather” usually do “flock together” in human relationships, finding a person with different immune system genes is beneficial for reproductive success.

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Chapter Reflections

This chapter began with a story about mice with different fur color and weight, which you might not have expected to see in a textbook about psychology. We hope that this story, and others like it in this chapter, emphasized the need to look at the actions of nature and nurture as insepa- rable, intertwined influences on the human mind. Although we discussed the nuts and bolts of the biological influences shaping our mind throughout its history, at no time did we argue that these physical forces act alone. The developmental perspective of psychology reminds us about the immaturity of the newborn human, requiring the long period of nurture that helped shape interactions between men and women. In understanding how nurture can impact nature, we can more clearly see why even identical twins become less alike over the course of their lifespan. With the help of social psychology and the evolutionary perspective, we gain a greater understanding of ourselves not as “rugged individualists” but, rather, as individuals bound to one another for our very survival as a species. The notion of altruism, of helping others, operates on both the genetic and social levels. We see that the mere action of “helping” can only be fully understood through learning more about how nature and nurture interact. The mere prospect of going on a date, and whom we choose to date, has deep roots in this nature-nurture relationship as well. Greater knowledge of sexual selection tendencies of males and females might help to explain why you are (or are not) attracted to those around you, or why you some- times get stuck in the “friend zone”—that unpleasant place where you are viewed as a friend but want to be more. Mysteries like the friend zone may be unraveled with a closer look at how specific facial features, humor, body odor, or the words we use influence such personal relations. Viewing nature and nurture as interacting influences on our behavior reassures us that we are not somehow helpless captives of our genes. They are certainly an important part of who we are, but our choices and experi- ences make major contributions to the final product as well. <

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Chapter 3 | THE EVOLVING MIND: NATURE AND NURTURE INTERTWINED122

physical ffororces acact t ala onne.e The e ded veloopmpmental pep rspectivve e ofo psysychchoo remindnds s us aabooutt thhe immmmatuuriity ofof thhe newwboborrn humuman, rer quuiririing long ppeeriod of nnururtuture thahat t hehelpeed shahapepe inttereracacttionns beettweee nn memenn wwomeen.n. IIn unu derrstanding hohow nuurtrturure cacan immpapactct nnataturu e,e, wwe caan m clearly see why even identical twins bbecome less allike over the cour their liifefespan.

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F O S T E R , C E D R I C 1 6 9 2 T S

KEY TERMS The Language of Psychological Science Be sure you can define these terms and use them correctly. adaptation, p. 107 allele, p. 93 altruism, p. 113 behavioral genetics, p. 99 culture, p. 116 dominance, p. 93 epigenetics, p. 98 evolution, p. 105 evolutionary psychology, p. 112

fitness, p. 107 gene, p. 92 gene expression, p. 92 genetic drift, p. 106 genotype, p. 92 heritability, p. 99 heterozygous, p. 93 homozygous, p. 93 migration, p. 106

mutation, p. 106 natural selection, p. 105 nature, p. 89 nurture, p. 89 phenotype, p. 92 recessiveness, p. 93 reciprocal altruism, p. 114 relatedness, p. 95 sexual selection, p. 115

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