Nature or Nurture
Manita123
ch09.pptxChapter 9
BIOLOGICAL FOUNDATIONS OF PERSONALITY
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© 2018 John Wiley & Sons, Inc. This presentation may be used and adapted for use in classes using the fourteenth edition of Personality. It may not be re-distributed except to students enrolled in such classes and in such case must be password protected to limit access to students enrolled in such classes. Students may not re-distribute portions of the original presentation.
QUESTIONS TO BE ADDRESSED IN THIS CHAPTER
How, and why, do infants differ in temperament?
How can the study of human evolution inform our understanding of the personalities of contemporary humans?
What role do genes play in the formation of personality? How do they interact with the environment in the unfolding of personality?
What is the relation between brain processes and personality processes involving mood and self-concept?
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TEMPERAMENT: VIEWS OF MIND-BODY RELATIONSHIPS FROM THE PAST TO THE PRESENT
Scientific understanding of biological bases of personality has benefited from an accident experienced by Phineas Gage, in railroad construction
On-the-job explosion blew an iron rod through his left cheek, the base of his skull, and the front of his brain
Largely destroyed a part of his frontal cortex, then exited through the top of his head
Gage was stunned but not killed, yet his personality changed deeply
Suggests that there exist deep interconnections between brain functioning and personality functioning
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TEMPERAMENT: constitution and temperament: early views
Gall’s phrenology:
Tried to locate areas of the brain responsible for emotional and behavioural functioning
Did post-mortem inspections of brains to relate differences in brain tissues to reports of the individuals capacities and dispositions before death
Contemporary research indicates that the brain doesn’t work in the way Gall had assumed
Most complex actions and thoughts patterns are executed by the synchronized action of multiple, interconnected regions of the brain
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TEMPERAMENT: constitution and temperament: early views
Gall’s phrenology:
Tried to locate areas of the brain responsible for emotional and behavioural functioning
Did post-mortem inspections of brains to relate differences in brain tissues to reports of the individuals capacities and dispositions before death
Contemporary research indicates that the brain doesn’t work in the way Gall had assumed
Most complex actions and thoughts patterns are executed by the synchronized action of multiple, interconnected regions of the brain
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TEMPERAMENT: VIEWS OF MIND-BODY RELATIONSHIPS FROM THE PAST TO THE PRESENT
In 20th century, investigators in Europe and US were intrigued by the possibility of systematic links between psychological temperament and body types
Kretschmer’s three fundamental body types: pyknic (plum), athletic, and asthenic (frail)
US: Similar efforts by William Sheldon, who also suggested that physique was systematically related to temperament
Of more lasting value: the work of Pavlov, who examined how the nervous system of organisms is modified by experience
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TEMPERAMENT: CONSTITUTION AND TEMPERAMENT: LONGITUDINAL STUDIES
New York Longitudinal Study (NYLS) followed over 100 children from birth to adolescence, using parental reports of infants' reactions to a variety of situations to define variations in infant temperament
Defined three infant temperament types:
Easy babies who were playful and adaptable
Difficult babies who were negative and unadaptable
Slow-to-warm-up babies who were low in reactivity and mild in their responses
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TEMPERAMENT: CONSTITUTION AND TEMPERAMENT: LONGITUDINAL STUDIES
NYLS found a link between such early differences in temperament and later personality characteristics
Difficult babies found to have the greatest difficulty in later adjustment
Easy babies found to have the least likelihood of later difficulties
Parental environment best suited for babies of one temperament type might not be best for those of a different temperament type
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TEMPERAMENT: CONSTITUTION AND TEMPERAMENT: LONGITUDINAL STUDIES
Buss and Plomin (1975, 1984) used parental ratings of behavior to define 4 dimensions of temperament
Emotionality
Activity
Sociability
Impulsivity
(Impulsivity later dropped because not found as a clear dimension in subsequent factor analyses)
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TEMPERAMENT: CONSTITUTION AND TEMPERAMENT: LONGITUDINAL STUDIES
Buss and Plomin found that temperament shows evidence of
Continuity over time
Being largely inherited
However, research was problematic in the use of parental ratings rather than more objective measures of observation
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Inhibited and Uninhibited Children: Research of Kagan and Colleagues
Harvard psychologist Jerome Kagan observed children directly, commonly in laboratory settings
Observed two clearly defined behavioral profiles in temperament: inhibited and uninhibited profiles
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Inhibited and Uninhibited Children: Research of Kagan and Colleagues
Inhibited child:
Reacts to unfamiliar persons or events with restraint, avoidance, and distress
Takes a longer time to relax in new situations
Has more unusual fears and phobias
Uninhibited child
Seems to enjoy these very same situations
Responds with spontaneity in novel situations, laughing and smiling easily
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Inhibited and Uninhibited Children: Research of Kagan and Colleagues
Hypothesis: infants inherit differences in biological functioning that lead them to be more or less reactive to novelty
Videotaped 4-month-old infants’ behavior while they were exposed to familiar and novel stimuli
Videotapes then scored on measures of reactivity
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Inhibited and Uninhibited Children: Research of Kagan and Colleagues
Found that
≈ 20 % designated as high-reactive
≈ 40 % low-reactive
Remaining infants showed various mixtures of response
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Inhibited and Uninhibited Children: Research of Kagan and Colleagues
Hypothesis: Inherited differences tend to be stable during development
Again studied the children when they were 14 months old, 21 months old, and 4 ½ years old
High-reactive infants, relative to low-reactive infants, showed
Greater fearful behavior
Greater heart acceleration
Increased blood pressure in response to the unfamiliar at 14 and 21 months
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Inhibited and Uninhibited Children: Research of Kagan and Colleagues
Differences between high- and low-reactive infants were maintained at age 4 ½ years of age
Further testing in the eighth year of life indicated continuing consistency
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Inhibited and Uninhibited Children: Research of Kagan and Colleagues
Although there is consistency across time in temperament, there is also evidence of change
Many high-reactive infants did not become fearful
Change seemed tied to having mothers who were not overly protective and placed reasonable demands on them
Some low-reactive infants lost their relaxed style
Despite an initial temperamental bias, environment played a role in the unfolding personality
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Schwartz et al. (2003) studied a group of young adults who had been categorized as being highly inhibited or uninhibited when they were only two years old
Prediction: inhibited people would respond more to pictures of novel, unfamiliar faces in a laboratory study
fMRI employed to determine the exact brain regions that became active
When they viewed the novel faces, adults who had been identified as inhibited children showed higher levels of amygdala reactivity
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Interpreting Data on Biology and Personality
Three interpretations would be over-interpretations
The amygdala is a kind of fear-production machine
The amygdala can be involved in many psychological functions other than fear responses
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Interpreting Data on Biology and Personality
The amygdala is the only biological mechanism in fear responses
It is possible that many other systems are involved, too
Anderson and Phelps (2002) demonstrated that people with amygdala damage experienced the same range of emotions as did biologically normal persons
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TEMPERAMENT: BIOLOGY, TEMPERAMENT AND PERSONALITY DEVELOPMENT: CONTEMPORARY RESEARCH
Interpreting Data on Biology and Personality
The environment is unimportant
Fox et al. (2005) provide clear evidence that the link from genetics to behavioral inhibition in childhood depended on social support
It is always genes and environment rather than genes versus environment
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
Two types of biological causes of a behavior
Proximate causes refer to biological processes operating in the organism at the time the behavior is observed
Ultimate causes: Why is a given biological mechanism a part of the organism, and why does it respond to the environment in a given way (e.g., natural selection)?
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
Ultimate causes are grounded in the basic principle that some biological features are better than others, at least for organisms living in a given environment
Organisms who possess those features are more likely to survive, to reproduce, and thus to be the ancestors of future generations
Across a number of generations, the population as a whole is increasingly populated by beings who possess the adaptive biological mechanism
The biological mechanism evolves
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Contemporary human functioning is understood in relation to evolved solutions to adaptive problems faced by the species over millions of years
Basic psychological mechanisms are the result of evolution by selection
Fundamental components of human nature can be understood in terms of evolved psychological mechanisms that have adaptive value in terms of survival and reproductive success
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
The features of mind that evolved are ones that solve recurrent problems that are important to reproductive success (e.g., a pair of eyes that enables us to see in depth)
Evolved mental mechanisms are adaptive to the way of life of hundreds of centuries ago, when our ancestors were hunters and gatherers
Implication: we may have evolved psychological tendencies that no longer are good for us (e.g., our taste preference for fat)
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolved psychological mechanisms are domain-specific (e.g., we fear specific stimuli that have been threats to humans across the course of evolution)
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
The mind contains multiple information processing devices called mental "modules" (Fodor, 1983), each of which processes information from one specific domain of life
Example: the task of attracting mates is a distinct problem of great evolutionary significance
To solve it, we purportedly have evolved a module that comes into play when we face problems having to do with mate attraction
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Social Exchange and the Detection of Cheating
Which psychological mechanisms have evolved through selection and which adaptive problems did they evolve to solve?
Leda Cosmides (1989) "social exchange" of goods and services
Cosmides: cheating detection is of such great survival value that the mind contains distinct systems for the detection of cheaters
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Social Exchange and the Detection of Cheating
More recent work suggests that the ability to solve cheating problems is a human universal
Found among nonliterate participants living in cultures that are isolated from the industrialized world
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Sex Differences: Evolutionary Origins?
Drawing conclusions about psychological differences between men and women is very tricky
One interpretation is that biology causes sex differences
Men and women also differ socially
A core idea of evolutionary psychology is that biology determines sex differences
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Male-Female Mate Preferences
Parental investment theory (Trivers, 1972):
Biological differences between the sexes cause women to invest more in parenting
Can pass their genes on to fewer offspring than men potentially can
Limited time periods during which they are fertile
More limited age range during which they can produce offspring
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Male-Female Mate Preferences
Parental investment theory (Trivers, 1972):
Women carry the biological burden of pregnancy, which lasts for nine months
Men can be involved in multiple pregnancies at the same time
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Male-Female Mate Preferences: Buss
Females will have stronger preferences about mating partners than will males
Males and females will have different criteria for the selection of mates
Women seek men who have potential for providing resources and protection
Men focus on reproductive potential of a partner
These preferences should be evident in current social patterns
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Male-Female Mate Preferences: Buss
Parental probability theory:
Women can always be sure that they are the mothers of the offspring
Males cannot be so sure
Thus males have greater concerns about sexual rivals and place greater value on chastity in a potential mate than do females
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Male-Female Mate Preferences: Specific hypotheses from parental investment and parenthood probability theories
A woman's "mate value" for a man should be determined by her reproductive capacity and chastity
A man's "mate value" for a woman should be determined the resources he can supply
Males and females should differ in the events that activate jealousy
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Male-Female Mate Preferences
Buss (1989)’s data: 37 samples, representing over 10,000 individuals, from 33 countries located on 6 continents and 5 islands:
In each of the 37, males valued physical attractiveness and relative youth in potential mates more than did females
Males’ preference for chastity in potential mates found in 23 out of the 37 samples
In 36 samples, females found to value the financial capacity of potential mates relatively more than males
Valued ambition and industriousness to a greater extent than males in 29 of 37 samples
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Causes of Jealousy
Three studies tested the hypothesis of sex differences in jealousy (D. M. Buss et al., 1992)
Undergraduates asked whether they would experience greater distress in response to sexual infidelity or emotional infidelity
60% of the male sample reported greater distress over a partner's sexual infidelity
83 % of the female sample reported greater distress over a partner's emotional attachment to a rival
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Causes of Jealousy
Physiological measures of distress were taken on undergraduates who imagined partner becoming sexually vs. emotionally involved with someone else
Males showed greater distress to partner's sexual involvement
Women showed greater distress partner's emotional involvement
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Causes of Jealousy
Hypothesis: males and females who had experienced committed sexual relationships would show the same results as in the previous study but to a greater extent than would males and females who had not been involved in such a relationship
This was found to be the case for males but not for females
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Origins of Sex Differences: How Strong Are the Data?
Eagly and Wood (1999) reanalyzed data from a multinational study of men's and women's preferences in mates
Some findings contradicted evolutionary psychology
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Origins of Sex Differences: How Strong Are the Data?
Eagly and Wood found that in societies with greater gender equality:
Women were less concerned with men's earning capacity
Men were less concerned with women's housekeeping skills
Data were consistent with a biosocial view of sex differences
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Origins of Sex Differences: How Strong Are the Data?
Miller, Putcha-Bhagavatula, & Pedersen (2002) re-analyzed Buss and colleagues’ mate-preference data
“[A]cross the data, what men desired most in a mate women desired most in a mate. [There were] extraordinarily high correlations between men's and women's ratings for both short-term and long-term sexual partners" (p. 90)
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Origins of Sex Differences: How Strong Are the Data?
DeSteno, Bartlett, Braverman, & Salovey (2002) suggest that evolutionary psychologists’ findings may have been a methodological artifact
Participants asked if they would be more distressed if partner (a) had sexual relations with another person or (b) formed a close emotional bond with another person
Over the course of human evolution people were not frequently faced with learning simultaneously about a partner's sexual and emotional relations
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Origins of Sex Differences: How Strong Are the Data?
DeSteno and colleagues (2002) asked participants to consider the sexual and emotional scenarios one at a time and to indicate how upset they would be by each one
Sex differences in jealousy were no longer found
Both were more distressed by sexual infidelity than by news of a partner's emotionally close nonsexual relationship
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Origins of Sex Differences: How Strong Are the Data?
Harris (2000): analysis of men's and women's physiological responses to imagining sexual versus emotional infidelity
Women not found to be more responsive to emotional (versus sexual) infidelity
Men did respond strongly to sexual infidelity but may have resulted from the idea that sex occurred
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Origins of Sex Differences: How Strong Are the Data?
Harris (2000) indeed found that men responded strongly to imagined sexual encounters whether or not infidelity was involved
Subsequent work similarly failed to find the sex differences predicted by evolutionary psychology
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Origins of Sex Differences: How Strong Are the Data?
Recent study of differences in personality between males and females provided support for an evolutionary interpretation of sex differences
Schmitt, Realo, Voracek, & Allik, 2008 assessed males and females on the Big Five traits across 55 nations, including both more developed, egalitarian countries and less developed, less egalitarian countries
Women were found to be higher on neuroticism, extraversion, agreeableness, and conscientiousness
Differences were greater in the developed, egalitarian cultures than in the less developed, less egalitarian cultures
Perhaps differences between males and females become greater when behavior is less constrained by social roles and where inherent differences are able to naturally diverge
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Theory and the Big Five Personality Dimensions
In Goldberg’s (1981, 1990) lexical hypothesis, trait terms emerged to help people categorize behaviors fundamental to the human condition
Then and now, may be important to know whether people are:
Active and dominant or passive and submissive? (E)
Agreeable or disagreeable? (A)
Able to be counted on? (C)
Unpredictable or emotionally stable? (N)
Smart? (O)
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY PSYCHOLOGY
Evolutionary Theory and the Big Five Personality Dimensions
Evolutionary psychology potentially explains why these five individual differences are noticed and discussed when people observe and describe others
But, difficult to reconcile the two perspectives if Big Five treated as causal;
Units of analysis in evolutionary psychology and in five-factor theory differ fundamentally:
Evolutionary psychology: basic units of analysis domain-specific
Five-factor theory: domain-general
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY EXPLANATIONS: COMMENT
Investigators differ concerning the degree to which evolutionary psychology can provide a basis for the analysis of personality
Buss suggests that an evolutionary framework offers virtually the only hope for bringing the field of psychology into some kind of theoretical order
Human behavior depends on psychological mechanisms and the only known cause of such mechanisms is evolution by natural selection
The biological roots of human nature, as expressed in the genes, are the link between evolution and behavior
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY EXPLANATIONS: COMMENT
Others suggest humans much more free of genetically programmed responses
Cantor (1990): evolutionary psychologists have ignored much of the diversity of social interaction and efforts to solve contemporary problems
Eagly and Wood (1999): sex differences emphasized by Buss and others can be accounted for by the different roles demanded of men and women
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EVOLUTION, EVOLUTIONARY PSYCHOLOGY, AND PERSONALITY
EVOLUTIONARY EXPLANATIONS: COMMENT
Many feminists: Buss's interpretation of sex differences data suggests that they are inevitable
Some biologists: evolutionary psychologists have overstated the impact of evolutionary mechanisms on human thought and action and underestimated person-environment interactions
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GENES AND PERSONALITY
BEHAVIORAL GENETICS = The study of genetic contributions to behavior
Selective Breeding Studies
Animals with a desired trait for study are selected and mated to produce a strain of animals that is consistent within itself for the desired characteristic
One can study their typical behavioral tendencies and/or subject the different strains to different experimentally controlled developmental experiences
Researchers then can sort out the effects of genetic differences and environmental differences on the observed later behavior
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Twin Studies
Twins provide a naturally occurring experiment
If 2 organisms are identical genetically, later differences can be attributed to differences in environments
If 2 organisms are different genetically but experience the same environment, differences can be attributed to genetic factors
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Twin Studies
Identical (monozygotic) twins and fraternal (dizygotic) twins offers a good approximation to this research ideal
MZ twins are genetically identical
DZ twins are as genetically similar as any pair of siblings, on the average sharing about 50 percent of their genes
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Twin Studies
Difference in similarity between MZ twin pairs and DZ twin pairs is crucial to estimating the effects of genetics
If genetics influence a given personality characteristic, then MZ twins should be more similar on the given personality characteristic than are DZ twins
If not, no genetic effect
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Twin Studies
MZ and DZ twins sometimes are reared apart as in the case of adoption
International data set that features large numbers of reared-apart twins who have completed various psychological measures (Bouchard, Lykken, McGue, Segal, & Tellegen, 1990)
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Twin Studies
Results of studies in which MZ and DZ twins are reared apart provide clear evidence that the effects of biology endure across different circumstances
Twin correlations indicate the degree of similarity between the twins were in the .45 to .50 range
MZ twins raised apart were about as similar to one another as were MZ twins raised together
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Adoption Studies
Are biological siblings more similar to one another than are the adoptive siblings?
Are they more similar to the parents than the adoptive siblings?
Are the adoptive siblings are more similar to their biological parents than to their adoptive parents?
A "yes" answer to such questions would be suggestive of the importance of genetic factors
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Heritability Coefficient
h2: proportion of observed variance in scores that can be attributed to genetic factors
Based on the difference between the MZ and DZ correlations
If MZ twins are no more similar to one another than are DZ twins then h2 is zero
If MZ twins differ greatly from DZ twins, h2 is large
Refers to variation in the population examined in a given study
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Heritability Coefficient
h2 : Two implications:
Different h2s may be observed in different populations
h2 does not indicate degree to which genetics accounts for a particular individual’s characteristics
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Heritability of Personality: Findings
Pattern of results strongly suggests an important role for heredity in almost all aspects of personality functioning
Criticism: most studies are based on self-report questionnaire methods
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Heritability of Personality: Findings
Riemann, Angleitner, & Strelau (1997): two independent peer reports as well as self-reports on the NEO Five-Factor Inventory were collected on a sample of 660 MZ twins and 304 DZ twins
Found reliability in peer-peer rating, in self-peer rating
Found general support for earlier findings concerning genetic influence on all of the Big Five personality factors
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Some Important Caveats
An overall heritability estimate of 40 percent for personality would not mean that:
40 percent of one's personality is inherited
40 percent of some aspect of one's personality is inherited
40 percent of the difference in personality between two individuals or groups of people is inherited
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Some Important Caveats
h2 is a population statistic that varies with:
The characteristic measured
How the characteristic is measured
The age and other characteristics of the population investigated
Whether twin or adoption data are used
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Some Important Caveats
Even if something is altogether determined by heredity, this does not mean that it cannot be altered by the environment
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Molecular Genetic Paradigms
Molecular genetic techniques involve an effort to identify specific genes that are linked with personality traits
By examining the genetic material of different individuals, researchers hope to show how genetic variations, or alleles, relate to individual differences in personality functioning
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GENES AND PERSONALITY
BEHAVIORAL GENETICS
Molecular Genetic Paradigms
Research by Caspi and colleagues has discovered molecular-genetic factors that make individuals more or less vulnerable to becoming depressed
Individuals who were genetically predisposed to have lower levels of serotonergic activity AND who experienced numerous stressful life events were much more likely to become depressed than were other individuals
Gene X Environment interaction
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GENES AND PERSONALITY
ENVIRONMENTS AND GENE-ENVIRONMENT INTERACTIONS
Shared and Nonshared Environment
Shared environments: those shared by siblings as a result of growing up in the same family
Nonshared environments: those not shared by siblings growing up in the same family
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GENES AND PERSONALITY
ENVIRONMENTS AND GENE-ENVIRONMENT INTERACTIONS
Shared and Nonshared Environment
If shared environments are important, then
Biological siblings raised together will be more similar than biological siblings raised apart and should be more similar to biological parents than are siblings raised apart
Two adopted siblings raised together should be more similar than if they were raised apart
If nonshared environments are important, then biological siblings raised together will be no more similar than if they were raised apart
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GENES AND PERSONALITY
ENVIRONMENTS AND GENE-ENVIRONMENT INTERACTIONS
Shared and Nonshared Environment
Nonshared environments appear to be far more important for personality development than the shared experiences resulting from being in the same family:
≈ 40% of variations in personality traits due to genetic factors
≈ 35 % due to the effects of nonshared environments
≈ 5% due to shared environments
(the rest due to measurement error)
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GENES AND PERSONALITY
ENVIRONMENTS AND GENE-ENVIRONMENT INTERACTIONS
Shared and Nonshared Environment
Loehlin, McCrae, Costa, and John (1998) examined genetic and environmental effects in three different measures of the Big Five
Individual differences in A, C, and O were just as heritable as individual differences in E and N
Findings were independent of the effects of intellectual ability; Openness found to be independent of intelligence, with its own genetic basis
Having available three measures for each Big Five factor made it possible to test generalizability across instruments
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GENES AND PERSONALITY
ENVIRONMENTS AND GENE-ENVIRONMENT INTERACTIONS
Understanding Nonshared Environment Effects
Recent research (Reiss, 1997; Reiss, Neiderhiser, Hetherington, & Plomin, 1999) focused on the processes linking genetic, family, and social influences on personality development during adolescence
Seeks to separate out the effects of parenting common to siblings in a family from the effects of parenting unique to each sibling
Much of the parenting unique to each child seems to be due to the genetic characteristics of that child
Differences in the way parents treat each child seem to be due to different behaviors evoked in the parent by that child
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GENES AND PERSONALITY
ENVIRONMENTS AND GENE-ENVIRONMENT INTERACTIONS
Understanding Nonshared Environment Effects
Does the suggestion that children from the same family are different because of the effects of nonshared environments mean that family experiences are unimportant?
No; family influences are important, as are experiences outside the family, but it is the experiences unique to each child that are important rather than the experiences shared by children in the same family
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GENES AND PERSONALITY
ENVIRONMENTS AND GENE-ENVIRONMENT INTERACTIONS
Three Kinds of Nature-Nurture Interactions
The same environmental experiences may have different effects on individuals with different genetic constitutions
Individuals with different genetic constitutions may evoke different responses from the environment
Individuals with different constitutions select and create different environments
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GENES AND PERSONALITY
ENVIRONMENTS AND GENE-ENVIRONMENT INTERACTIONS: A COMMENT ON THE RESEARCH REVIEWED
Every major trait researched shows evidence of a genetic component
There is little evidence of a shared environment effect
There is considerable evidence of a nonshared environment effect but the processes involved are unclear
Generally genes contribute to stability of personality and environment to change; genes can contribute to change and the environment can contribute to stability
Genes and environments always interact with one another
People select, perceive, and respond to environments in ways influenced by genetic factors and environmental forces differentially respond to individuals based on their genetic characteristics
Instead of asking how heritable a trait is, ask about the circumstances under which the genetic contributions to the trait are enhanced or suppressed
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CURRENT APPLICATIONS
CAUSES OF INDIVIDUAL DIFFERENCES: GENES, SOCIAL EXPERIENCE—OR SOMETHING ELSE?
Startling findings document a role for prenatal factors in determining sexual orientation
People who have more older brothers are, on average, somewhat more likely to have a homosexual rather than a heterosexual orientation; why?
The sexual orientation of males who were raised with varying numbers of older brothers living in their home was compared to the sexual orientation of a key comparison group: males who had the same number of older brothers, but whose brothers did not live in their household
The findings revealed that sexual orientation was predicted by the number of older siblings one has whether or not those siblings grew up in one’s own household!
The key influence is in the prenatal environment
As women have more male children, they may develop an immune system response to male fetuses.
This immune reaction could affect the biochemical environment of the subsequent male fetus, specifically influencing its brain development in such a way that the later child is less likely to develop a heterosexual orientation
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NEUROSCIENCE AND PERSONALITY
LEFT AND RIGHT HEMISPHERIC DOMINANCE
People differ – one from another and, for any given person, from one time to another – in the degree to which their emotional experience is positive versus negative
A possibility explored in research by Richard Davidson (1994, 1995, 1998) is that the left versus right hemispheres are differentially involved in positive versus negative emotion
Individual differences in prefrontal asymmetry were found to be associated with baseline mood
Left hemispheric dominance with positive affect
Right hemispheric dominance with negative affect
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NEUROSCIENCE AND PERSONALITY
LEFT AND RIGHT HEMISPHERIC DOMINANCE
Currently depressed and previously depressed individuals are found to have decreased left-anterior cortical activity relative to nondepressed individuals
Individuals with damage to the left-anterior brain region are likely to become depressed whereas those with damage to the right-anterior brain region are likely to become manic
Infants who experience greater distress upon separation from their mothers show greater right-sided prefrontal activation and lesser left-sided prefrontal activation than infants who show little distress in this
Sharot (2011) and colleagues: desirable and undesirable information are encoded in different parts of the brain; extreme optimists differ from pessimists in that their brains process undesirable information to a lesser extent
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NEUROSCIENCE AND PERSONALITY
LEFT AND RIGHT HEMISPHERIC DOMINANCE
Inhibited children show more reactivity in their right hemisphere and uninhibited children dominance in the left hemisphere
EEG measures can differentiate between two different negative emotions: anxious arousal during a task and worrying prior to a task
Worrying is associated with stronger left-frontal brain activation than is anxious arousal
Worrying is “a unique emotional state” (Hafmann et al., 2005, p. 472)
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NEUROSCIENCE AND PERSONALITY
NEUROTRANSMITTERS AND TEMPERAMENT : DOPAMINE AND SEROTONIN
Dopamine appears to be central to the functioning of the reward system
Serotonin also is involved in the regulation of mood
SSRIs, selective serotonin reuptake inhibitors, are thought to alleviate depression through their prolongation of the action of serotonin at the synapses of neurons
The hormone cortisol is associated with the stress response
The fact that neurotransmitters contribute to mood suggests that an analysis of brain chemistry can illuminate individual differences in temperament
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NEUROSCIENCE AND PERSONALITY
NEUROTRANSMITTERS AND TEMPERAMENT : DOPAMINE AND SEROTONIN
Three Dimensions of Temperament: PE, NE, and DvC
Clark and Watson's (1999) model: individual differences in temperament can be summarized in terms of three superfactors similar to those suggested by Eysenck and also corresponding to three of the Big Five dimensions
NE (Negative Emotionality), PE (Positive Emotionality), and DvC (Disinhibition versus Constraint)
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NEUROSCIENCE AND PERSONALITY
NEUROTRANSMITTERS AND TEMPERAMENT : DOPAMINE AND SEROTONIN
Three Dimensions of Temperament: PE, NE, and DvC
High on NE: elevated levels of negative emotions; see the world as threatening, problematic, and distressing
Low on NE: calm, emotionally stable, self-satisfied
High on PE: willingness to engage the environment, enjoyment of company of others, energy, cheerfulness, enthusiasm
Low on PE: reserved, socially aloof, low in energy and confidence
High on DvC: impulsive, reckless, oriented toward feelings and sensations of the moment
Low on DvC: careful, avoidant of risk or danger
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NEUROSCIENCE AND PERSONALITY
NEUROTRANSMITTERS AND TEMPERAMENT : DOPAMINE AND SEROTONIN
Three Dimensions of Temperament: PE, NE, and DvC
PE associated with the action of dopamine
High dopamine levels associated with approach behaviors whereas deficits in dopamine associated with deficits in incentive motivation
Differences in hemispheric lateralization, with high PE scores being associated with left hemispheric dominance, may also be involved (Davidson, 1992, 1994, 1998)
The biological basis of DvC may be serotonin
Humans low in serotonin tend to be aggressive and to show increased use of dopamine-activating drugs such as alcohol
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NEUROSCIENCE AND PERSONALITY
NEUROTRANSMITTERS AND TEMPERAMENT : DOPAMINE AND SEROTONIN
Three Dimensions of Temperament: PE, NE, and DvC
Less is known about the neurobiology underlying NE
However, there is a relation between low serotonin levels at the neuron synapses and depression, anxiety, and obsessive-compulsive symptoms
Hamer and Copeland (1998) relate low serotonin levels to a dark view of the world
Animals low in serotonin are excessively irritable
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NEUROSCIENCE AND PERSONALITY
NEUROTRANSMITTERS AND TEMPERAMENT : DOPAMINE AND SEROTONIN
Three Dimensions of Temperament: PE, NE, and DvC
No one-to-one correspondence between biological processes and personality traits
Each biological component appears to be associated with expression of more than one trait
Expression of each trait is influenced by more than one biological factor
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PLASTICITY: BIOLOGY AS BOTH CAUSE AND EFFECT
Evidence indicates that the brain does change as a result of experience
Draganski et al. (2004) used brain imaging techniques to obtain anatomical depictions of the brains of a group of participants
Then divided the group in half at random, and asked one-half of the participants to learn how to juggle over a period of 3 months
At the end of this time period, both groups, jugglers and non-jugglers, returned to the lab for a second brain scan
The brain imaging technique revealed that jugglers experienced a significant expansion of grey matter in the brain, in particular in a brain region involved in the perception of motion
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NEUROSCIENTIFIC INVESTIGATIONS OF “HIGHER-LEVEL” PSYCHOLOGICAL FUNCTIONS
BRAIN AND SELF
Are there functionally distinct systems in the brain that come into play when we are thinking about ourselves as opposed to thinking about other people or things?
Kelley et al., (2002) used fMRI to identify specific regions of the brain that are active when people rated trait adjectives
Participants judged
(1) whether the adjective was in uppercase letters
(2) whether the adjective described George W. Bush
(3) whether the adjective described themselves
Compared to baseline recordings, fMRI indicated that medial prefrontal cortex (PFC) was more involved in judgments about the self than about Bush or the typeface of the letters
Multiple brain regions surely come into play when people engage in any complex mental activity involving self-reflection
Yet, the findings provide intriguing initial evidence that neuroscientific research can inform complex questions about personality functioning
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