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A Four-Legged Co-Work...",e'-'-r _ Declan lies on his back wanting his belly scratched. The eight-year-old black Labrador cross' swings his legs in the air for a few minutes before resigning himself to chewing on someone's shoe.

In the office he behaves like any pet dog, but in the field he is like a tornado-focused on finding illegal drugs being smuggled. Declan is a drug-detector dog for the Customs Service and has been busting drug smugglers with his handler, Kevin Hattrill, for eight years.

Airport passengers look on with curiosity as Declan darts around people and their luggage. Within minutes he sniffs out a person of interest, who is taken away and questioned by airport authorities.

Dogs like Declan are trained to detect illegal drugs, such as cannabis, methamphetamine, and cocaine, or explosives. Hattrill said the dogs were dual response- trained when they detected something. "If the odor is around a passenger, they are trained to sit beside them. If it's around cargo, they are trained to scratch. When they detect something, their whole tempera- ment will change.

"The dogs can screen up to 300 people within 10 to 15 minutes at the airport. Nothing else can do that." (McKenzie-McLean,2006,p. 7) •

CHAPTER OUTLINE

i')r1J .~ie. 15 lassical Conditioning e Basics of Classical Conditioning

;. oplying Conditioning Principles to Human Behavior

inction

e eralization and Discrimination

_0 LIJF: t6_ rant Conditioning

;: Basics of Operant Conditioning s'tive Reinforcers, Negative Reinforcers, and Punishment

ros and Cons of Punishment: Why Reinforcement 3eats Punishment ec les of Reinforcement: Timing Life's Rewards

:;' g: Reinforcing What Doesn't Come Naturally

ING AN INFORMED CONSUMER OF PSYCHOLOGY: Using ;< avior Analysis and Behavior Modification

rl! tIp 17~ ,. iitive Approaches to Learning .earning

.", ional Learning: Learning Through Imitation

::e in Television and Video Games: Does the Media's sage Matter?

G DIVERSITY: Does Culture Influence How We -?

5 on the Web of ... The Manager Who Doubled Productivity

earning-

Dedan's expertise did not just happen, of course. It is the result of painstaking training procedures-the same ones that are at work in each of our lives, illustrated by our ability to read a book, drive a car, play poker, study for a test, or perform any of the numerous activities that make up our daily routine. Like Decian, each of us must acquire and then refine our skills and abilities through learning.

Learning is a fundamental topic for psychologists and plays a central role in almost every specialty area of psychology. For example, a developmental psychologist might inquire, "How do babies learn to distinguish their mothers from other people?" whereas a clinical psychologist might wonder, "Why do some people learn to be afraid when they see a spider?"

Psychologists have approached the study of learning from several angles. Among the most fundarnen- tal are studies of the type of learning that is illustrated in responses ranging from a dog salivating when it hears its owner opening a can of dog food to the emotions we-feel when our national anthem is played. Other theories consider how learning is a consequence of rewarding circumstances. Finally, several other .\"" ,'\ approaches focus on the cognitive aspects of learning, or the thought processes that underlie learning. '/ /1

161

Classical

LEARNING OUTCOMES

'5.3 Explain extinction.

'5.4 Discuss stimulus generalization and discrimination.

Does the mere sight of the golden arches '- make you feel pangs of hunger and think a: does, you are displaying an elementary form sical conditioning. Classical conditioning hel phenomena as crying at the sight of a bride fearing the dark, and falling in love.

Classical conditioning is one of a numb learning that psychologists have identified, encompasses them all: learning is a relativelv behavior that is brought about by experience.

We are primed for learning from the be exhibit a primitive type of learning called ha:- is the decrease in response to a stimulus that presentations of the same stimulus. For exam: initially show interest in a novel stimulus, su -

]

toy, but they will soon lose interest if they see over. (Adults exhibit habituation, too: newlyweds s they are wearing a wedding ring.) Habituation per " that have stopped providing new information. Most learning is considerably more complex than habi

of learning has been at the core of the field of psycholo phers since the time of Aristotle have speculated on the ing, the first systematic research on learning was done a: twentieth century, when Ivan Pavlov (does the name ring framework for learning called classical conditioning.

'5.' Describe the basics of classical conditioning and how they relate to learning.

'5.2 Give examples of applying conditioning principles to human behavior.

Learning A relatively permanent change in behavior brought about by experience.

» LOl The Basics of Classical Conditioning In the early twentieth century, Ivan Pavlov, a famous Rus been studying the secretion of stomach acids and salivati to the ingestion of varying amounts and kinds of food. observed a curious phenomenon: sometimes stomach see would begin in the dogs when they had not yet eaten any of the experimenter who normally brought the food, or experimenter's footsteps, was enough to produce salivati

162 Chapter 5 LEARN I NG

::_ lov's genius lay in his ability to recognize the implications of this discov- He saw that the dogs were responding not only on the basis of a biological (hunger), but also as a result oflearning-or, as it came to be called, classi-

- nditioning. Classical conditioning is a type of learning in which a neu- stimulus (such as the experimenter's footsteps) comes to elicit a response being paired with a stimulus (such as food) that naturally brings about

response. -=- demonstrate classical conditioning, Pavlov (1927) attached a tube - " salivary gland of a dog, allowing allow him to measure precisely - g's salivation. He then rang a bell and, just a few seconds later, pre-

the dog with meat. This pairing occurred repeatedly and was care- planned so that, each time, exactly the same amount of time elapsed

n the presentation of the bell and the meat. At first the dog would _ e only when the meat was presented, but soon it began to salivate ...sound of the bell. In fact, even when Pavlov stopped presenting the • he dog still salivated after hearing the sound. The dog had been cally conditioned to salivate to the bell.

- - .ou can see in Figure 1, the basic processes of classical conditioning - cnderlie Pavlov's discovery are straightforward, although the termi- - - . he chose is not simple. Consider first the diagram in Figure 1A. __ conditioning, there are two unrelated stimuli; the ringing of a bell

eat. We know that normally the ringing of a bell does not lead to - .on but to some irrelevant response, such as pricking up the ears

s: rhaps a startle reaction. The bell is therefare called the neutral i_lI:tIllUS because it is a stimulus that, before condltioning, does not naturally

- =- about the response in which we are interested. We also have meat, which _<illy causes a dog to salivate-the response we are interested in condi-

g. The meat is considered an unconditioned stimulus, or UCS, because - placed in a dog's mouth automatically causes salivation to occur. The

!I::5.:m15e that the meat elicits (salivation) is called an unconditioned response, -CR-a natural, innate, reflexive response that is not associated with

us learning. Unconditioned responses are always brought about by :-_esence of unconditioned stimuli.

: _~e 1B illustrates what happens during conditioning. The bell is rung ore each presentation of the meat. The goal of conditioning is for

;:og to associate the bell with the unconditioned stimulus (meat) and ·~~,,:nre to bring about the same sort of response as the unconditioned

us. After a number of pairings of the bell and meat, the bell alone the dog to salivate.

Ivan Pavlov (center) developed the principles of classical conditioning.

Classical conditioning A type of learning in which a neutral stimulus comes to bring about a response after it is paired with a stimulus that naturally brings about that response.

Neutral stimulus A stimulus that, before conditioning, does not naturally bring about the response of interest.

Unconditioned stimulus (UCS) A stimulus that naturally brings about a particular response without having been learned.

Unconditioned response (UCR) A response that is natural and needs no training (e.g., salivation at the smell of food).

STUDY ALERT Figure 1 (on the next page)

can help you learn and understand the process (and

terminology) of classical conditioning, which can be

confusing.

Module 15 CLASSICAL CONDITIONING 163

I II I I

Before Conditioning------------------.-----------Neutral stimulus Response unrelated to meat }

Sound of bell

Unconditioned stimulus (UCS) Unconditioned response (UCR)

Meat

Neutral stimulus Unconditioned response (UCR)

Sound of bell

Conditioned response (CR) I

ICUR 1 The basic process of classical conditioning. (A) Before conditioning, the ringing of a bell does not bring about salivation-making the bell a neutral stimulus. In contrast, meat naturally brings about salivation, making the meat an unconditioned stimulus and salivation an unconditioned response. (B)During conditioning, the bell is rung just before the presentation of the meat. (C) Eventually, the ringing of the bell alone brings about salivation. We now can say that conditioning has been accomplished: the previously neutral stimulus of the bell now is a conditioned stimulus that brings about the conditioned response of salivation.

164 Chapter 5 LEARNING

When conditioning is co evolved from a neutral stirn called a conditioned stirn time, salivation that occurs the conditioned stimulus conditioned response, or is depicted in Figure lC, then, the conditioned sf conditioned response.

The sequence and timing tion of the unconditioned _ conditioned stimulus are tant. Like a malfunctioninz at a railroad crossing that ~ train has passed by, a ne

follows an unconditioned _ chance of becoming a co::::; Ius. However, just as a war best if it goes on right befo neutral stimulus that is pr the unconditioned stimul - result in successful conditi 2006).

Although the terminolcr to describe classical condi - confusing, the following make the relationships . and responses easier to remember:

Conditioned = learn - • Unconditioned = not :.. • An unconditioned sf

unconditioned respo • Unconditioned stirn

response pairings are untrained.

• During conditioning tral stimulus is tra conditioned stimulus. A conditioned stimulus ditioned response, anc stimulus-conditioned ing is a consequence training. An unconditioned resr ditioned response are salivation in Pavlov' the unconditioned naturally, whereas response is learned.

> LOa Applying Conditioning Principles to Human Behavior

Conditioned stimulus (CS) Aonce- neutral stimulus that has been paired with an unconditioned stimulus to bring about a response formerly caused only by the unconditioned stimulus.

Conditioned response (CR) A response that, after conditioning, follows a previously neutral stimulus (e.g., salivation at the ringing of a bell).

Extinction Abasic phenomenon of learning that occurs when a previously conditioned response decreases in frequency and eventually disappears.

Although the initial conditioning experiments were carried out with ani- mals, classical conditioning principles were soon found to explain many aspects of everyday human behavior. Recall, for instance, the earlier illus- tration of how people may experience hunger pangs at the sight of McDon- ald's golden arches. The cause of this reaction is classical conditioning: the previously neutral arches have become associated with the food inside the restaurant (the unconditioned stimulus), causing the arches to become a conditioned stimulus that brings about the conditioned response of hunger.

Emotional responses are especially likely to be learned through classi- cal conditioning processes. For instance, how do some of us develop fears of mice, spiders, and other creatures that are typically harmless? In a now infamous case study, psychologist John B. Watson and colleague Rosalie Rayner (1920) showed that classical conditioning was at the root of such fears by condi- tioning an l l-month -old infant named Albert to be afraid of rats. "Little Albert," like most infants, initially was frightened by loud noises but had no fear of rats.

In the study, the experimenters sounded a loud noise just as they showed Little Albert a rat. The noise (the unconditioned stimulus) evoked fear (the unconditioned response). However, after just a few pairings of noise and rat, Albert began to show fear of the rat by itself, bursting into tears when he saw it. The rat, then, had become a CS that brought about the CR, fear. Furthermore, the effects of the conditioning lingered: five days later, Albert reacted with fear not only when shown a rat, but when shown objects that looked similar to the white, furry rat, including a white rabbit, a white sealskin coat, and even a white Santa Claus mask. (By the way, we don't know what happened to the unfortunate Little Albert. Watson, the experimenter, has been condemned for using ethically questionable procedures that could never be conducted today.)

Learning by means of classical conditioning also occurs during adulthood. For example, you may not go to a dentist as often as you should because of prior associations of dentists with pain. On the other hand, classical conditioning also accounts for pleasant experiences. For instance, you may have a particular fond- ness for the smell of a certain perfume or aftershave lotion because the feelings and thoughts of an early love come rushing back whenever you encounter it. Classical conditioning, then, explains many of the reactions we have to stimuli In the world around us.

Emotional responses are especially likely to be learned through classical conditioning processes.

L03 Extinction What do you think would happen if a dog that had become classically condi- tioned to salivate at the ringing of a bell never again received food when the bell was rung? The answer lies in one of the basic phenomena of learning: extinc- tion. Extinction occurs when a previously conditioned response decreases in frequency and eventually disappears.

To produce extinction, one needs to end the association between condi- tioned stimuli and unconditioned stimuli. For instance, if we had trained a dog to salivate (the conditioned response) at the ringing of a bell (the conditioned

Module 15 CLASSICAL CONDITIONING 165 c

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L04 Generalization and Discrimination Despite differences in color and shape, to most of us a rose is a rose is a rose. The pleasure we experience at the beauty, smell, and grace of the flower is similar for different types of roses. Pavlov noticed a similar phenomenon. His dogs often salivated not only at the ringing of the bell that was used during their original conditioning but at the sound of a buzzer as well.

Such behavior is the result of stimulus gener- alization. Stimulus generalization occurs when a conditioned response follows a stimulus that is similar to the original conditioned stimulus. The greater the similarity between two stimuli, the greater the likelihood of stimulus generalization. Little Albert, who, as we mentioned earlier, was conditioned to be fearful of white rats, grew afraid of other furry white things as well. However, according to the principle of stimulus generalization, it is unlikely that he would have been afraid of a black dog, because its color would have differentiated it sufficiently from the original fear-evoking stimulus.

On the other hand, stimulus discrimination occurs if two stimuli are fficiently distinct from each other that one evokes a conditioned response

ut the other does not. Stimulus discrimination provides the ability to dif- erentiate between stimuli. For example, my dog, Cleo, comes running into

e kitchen when she hears the sound of the electric can opener, which she learned is used to open her dog food when her dinner is about to be

rved. She does not bound into the kitchen at the sound of the food proces- r, although it sounds similar. In other words, she discriminates between e stimuli of can opener and food pro- sor. Similarly, our ability to discrimi- te between the behavior of a growling

and that of one whose tail is wagging lead to adaptive behavior=-avoiding

growling dog and petting the friendly e.

STUDY ALERT Remember that stimulus generalization relates to

stimuli that are similar to one another, while stimulus

discrimination relates to stimuli that are different

from one another.

The greater the similarity between two stimuli, the greater the likelihood of stimulus generalization.

Stimulus generalization Occurs when a conditioned response follows a stimulus that is similar to the original conditioned stimulus; the more similar the two stimuli are, the more likely generalization is to occur.

Stimulus discrimination The process that occurs if two stimuli are sufficiently distinct from each other that one evokes a conditioned response but the other does not; the ability to differentiate between stimuli.

Because of a previous unpleasant experience, a person may expect a similar occurrence when faced with a comparable situation in the future, a process known as stimulus generalization. Can you think of ways this process is used in everyday life?

Module 15 CLASSICAL CONDITIONINC 167

o erant LEARNING OUTCOMES

,6., Define the basics of operant conditioning.

,6.2 Explain reinforcers and punishment.

,6.3 Present the pros and cons of punishment.

,6.4 Discuss schedules of reinforcement.

,6'5 Explain the concept of shaping.

Operant conditioning Learning in which a voluntary response is strengthened or weakened, depending on its favorable or unfavorable consequences.

170 Chapter 5 LEARNING

Very good ... What a clever idea ... Fantastic. " you ... Excellent ... Super Right on ... This is - ever written; you get an A You ate really ge~ I'm impressed ... You're getting a raise ... Have a great ... I love you ...

Few of us mind being the recipient of any of the p But what is especially noteworthy about them is - simple statements can be used, through a proce conditioning, to bring about powerful changes "- teach the most complex tasks. Operant conditio . many of the most important kinds of human, and

Operant conditioning is learning in which a . is strengthened or weakened, depending on its fa able consequences. When we say that a response" ened or weakened, we mean that it has been made

to recur regularly. Unlike classical conditioning, in which the original be

ural, biological responses to the presence of a stimulus or pain, operant conditioning applies to voluntary re ~ organism performs deliberately to produce a desirable 0 operant emphasizes this point: the organism operates on . produce a desirable result. Operant conditioning is at w

that toiling industriously can bring about a raise or that exer in a good physique.

» toi The Basics of Operant Conditioning The inspiration for a whole generation of psychologists stud ditioning was one of the twentieth century's most influential : F. Skinner (1904-1990). Skinner was interested in specifying ies as a result of alterations in the environment.

Skinner conducted his research using an apparatus called (shown in Figure 1),a chamber with a highly controlled enviro to study operant conditioning processes with laboratory an' what happens to a rat in the typical Skinner box (Pascual & Ro _

Suppose you want to teach a hungry rat to press a lever that is in its box. At first the rat will wan- der around the box, exploring the environment in a relatively random fashion. At some point, however, it will probably press the lever by chance, and when it does, it will receive a food pellet. The first time this happens, the rat will not learn the connection between pressing a lever and receiving food and will continue to explore the box. Sooner or later the rat will press the lever again and receive a pellet, and in time the frequency of the pressing response will increase. Eventually, the rat will press the lever con- tinually until it satisfies its hunger, thereby demon- strating that it has learned that the receipt of food is contingent on pressing the lever.

Reinforcement: The Central Concept of Operant Conditioning

Food ------<~ dispenser Response --7.----; lever

FIGUR 1 B. F. Skinner with a Skinner box used to study operant conditioning. Laboratory rats learn to press the lever in order to obtain food, which is delivered in the tray.

Reinforcement The process by which a stimulus increases the probability that a preceding behavior will be repeated. Reinforcer Any stimulus that increases the probability that a preceding behavior will occur again.

Skinner called the process that leads the rat to con- tinue pressing the key "reinforcement" Reinforcement is the process by which a stimulus increases the probability that a preceding behavior will be repeated. In other words, pressing the lever is more likely to occur again because of the stimulus of food.

In a situation such as this one, the food is called a reinforcer. A reinforcer is any stimulus that increases the probability that a preceding behavior will occur again. Hence, food is a reinforcer because it increases the probability that the behavior of pressing (formally referred to as the response of press- ing) will take place.

What kind of stimuli can act as reinforcers? Bonuses, toys, and good grades can serve as reinforcers-if they strengthen the probability of the response that occurred before their introduction.

There are two major types of reinforcers. Aprimary reinforcer satisfies some biological need and works naturally, regardless of a person's prior experience. Food for a hungry person, warmth for a cold person, and relief for a person in pain all would be classified as primary reinforcers. A secondary reinforcer, in con- trast, is a stimulus that becomes reinforcing because of its association with a primary reinforcer. For instance, we know that money is valuable because we have learned that it allows us to obtain other desirable objects, including primary reinforcers such as ~oodand shelter. Money thus becomes a secondary reinforcer ..

Bonuses, toys, and good grades can serue as reinforcers-if they strengthen the probability of the ~esponse that occurred before their introduction.

l02 Positive Reinforcers, Negative Reinforcers, and Punishment In many respects, reinforcers can be thought of in terms of rewards; both a reinforcer and a reward increase the probability that a preceding response will occur again. But the term reward is limited to positive occurrences, and this is where it differs from a reinforcer-for it turns out that reinforcers can be positive or negative.

STUDY ALERT Remember that primary

reinforcers satisfy a biological need; secondary

reinforcers are effective due to previous association with

a primary reinforcer.

Module 16 OP~RANT CONDITIONING 171

Positive reinforcer A stimulus added to the environment that brings about an increase in a preceding response.

Negative reinforcer An unpleasant stimulus whose remolJa/leads to an increase in the probability that a preceding response will be repeated in the future.

Punishment A stimulus that decreases the probability that a previous behavior will occur again,

A positive reinforcer is a stimulus added to the environment that brin about an increase in a preceding response. If food, water, money, or praise provided after a response, it is more likely that that response will occur again i the future. The paychecks that workers get at the end of the week, for examp increase the likelihood that they will return to their jobs the following week.

In contrast, a negative reinforcer refers to an unpleasant stimulus whos removal leads to an increase in the probability that a preceding response wi be repeated in the future. For example, if you have an itchy rash (an unplea, ant stimulus) that is relieved when you apply a certain brand of ointme you are more likely to use that ointment the next time you have an itc rash. Using the ointment, then, is negatively reinforcing, because it remove the unpleasant itch. Negative reinforcement, then, teaches the individus that taking an action removes a negative condition that exists in the en ronment. Like positive reinforcers, negative reinforcers increase the likell hood that preceding behaviors will be repeated.

Note that negative reinforcement is not the same as punishme Punishment refers to a stimulus that decreases the probability that a prio behavior will occur again. Unlike negative reinforcement, which produce

an increase in behavior, punishment reduces the likelihood of a prior response If we receive a shock that is meant to decrease a certain behavior, then, we an receiving punishment, but if we are already receiving a shock and do som thing to stop that shock, the behavior that stops the shock is considered to negatively reinforced. In the first case, the specific behavior is apt to decre because of the punishment; in the second, it is likely to increase because of t negative reinforcement.

There are two types of punishment: positive punishment and negative p ishment, just as there are positive reinforcement and negative reinforcement. (ll both cases, "positive" means adding something, and «negative" means removin something.) Positive punishment weakens a response through the application an unpleasant stimulus. For instance, spanking a child for misbehaving, or spen ing 10 years in jail for committing a crime, is positive punishment. In con- trast, negative punishment consists of the removal of something pleasant. For instance, when a teenager is told she is "grounded" and will no longer be able to use the family car because of her poor grades, or when an employee is informed that he has been demoted with a cut in pay because of a poor job evaluation, negative punishment is being administered. Both positive and negative punishment result in a decrease in

othe likelihood that a prior behavior will be repeated. The following rules (and the summary in Figure 2) can

help you distinguish these concepts from one another:

• Reinforcement increases the frequency of the behavior pre- ceding it; punishment decreases the frequency of the behavior preceding it.

,. The application of a positive stimulus brings about an increase in the frequency of behavior and is referred to as positive

From the perspective Of ... A RETAIL SUPERVISOR How might you use the principles of operant conditioning to

change employee behavior involving tardiness, customer service, or store cleanliness?

172 Chapter 5 LEARNING

reinforcement; the application of a negative stimulus decreases or reduces the frequency of behavior and is called punishment.

• The removal of a negative stimulus that results in an increase in the frequency of behavior is negative reinforcement; the removal of a positive stimulus that decreases the frequency of behavior is negative punishment.

l03 The Pros and Cons of Punishment: Why Reinforcement Beats Punishment Is punishment an effective way to modify behavior? Punishment often pres- ents the quickest route to changing behavior that, if allowed to continue, might be dangerous to an individual. For instance, a parent may not have a second chance to warn a child not to run into a busy street, and so punishing the first incidence of this behavior may prove to be wise. Moreover, the use of punishment to suppress behavior, even temporarily, provides an opportu- nity to reinforce a person for subsequently behav- ing in a more desirable way.

Punishment has several disadvantages that make its routine use questionable. For one thing, punishment is frequently ineffective, particu- larly if it is not delivered shortly after the undesired behavior or if the indi- vidual is able to leave the setting in which the punishment is being given. An

Positive Reinforcement

, Increase in behavior (reinforcement)

Example: Giving a raise for good performance

Result: Increase in response of good performance

Positive Punishment

Decrease in behavior (punishment)

Example: Yelling at a teenager when she steals a bracelet

, Result: Decrease in frequency of response of stealing

FIGURE 2 Types of reinforcement and punishment.

Example: Applying ointment to relieve an itchy rash leads to a higher future likelihood of applying the ointment

Result: Increase in response of using ointment

Example: Teenager's access to car .! restricted by parents due to ' teenager's breaking curfew

Result: Decrease in response of breaking curfew

STUDY ALERT The differences between

positive reinforcement, negative reinforcement,

positive punishment, and negative punishment

are tricky, so pay special attention to Figure 2 and

the rules in the text.

Punishment has several disadvantages -that make its routine use questionable.

Module 16 OPERANT CONDITIONING 173

II

employee who is reprimanded by the boss may quit; a teenager who loses the use of the family car may borrow a friend's car instead. In such instances, the initial behavior that is being punished may be replaced by one that is even less desirable.

Even worse, physical punishment can convey to the recipient the idea that physical aggression is permissible and perhaps even desirable. A father who yells at and hits his son for misbehaving teaches the son that aggression is an appropriate, adult response. The son soon may copy his father's behavior by acting aggressively toward others. In addition, physical punishment is often administered by people who are themselves angry or enraged. It is unlikely that individuals in such an emotional state will be able to think through what they are doing or control carefully the degree of punishment they are inflicting (Baumrind, Larzelere, & Cowan, 2002; Sorbring, Deater-Deckard, & Palmerus, 2006).

In short, the research findings are clear: reinforcing desired behavior is a more appropriate technique for modifying behavior than using punishment (Hiby, Rooney, & Bradshaw, 2004; Sidman, 2006).

L04 Schedules of Reinforcement: Timing Life's Rewards The world would be a different place if poker players never played cards again after the first losing hand, fishermen returned to shore as soon as they missed a

catch, or telemarketers never made another phone call after their first hang- up. The fact that such unreinforced behaviors continue, often with great fre- quency and persistence, illustrates that reinforcement need not be received continually for behavior to be learned and maintained. In fact, behavior that is reinforced only occasionally can ultimately be learned better than can behavior that is always reinforced.

When we refer to the frequency and timing of reinforcement that fol- lows desired behavior, we are talking about schedules of reinforcement. Behavior that is reinforced every time it occurs is said to be on a continuous reinforcement schedule; if it is reinforced some but not all of the time, it is on a partial (or intermittent) reinforcement schedule. Although learn- ing occurs more rapidly under a continuous reinforcement schedule, behav- io~lasts longer after reinforcement stops when it is learned under a partial

reinforcement schedule (Staddon & Cerutti, 2003; Gottlieb, 2004; Casey, Cooper-Brown, & Wacher, 2006).

Why should intermittent reinforcement result in stronger, longer-lasting learning than con- tinuous reinforcement? We can answer the ques- tion by examining how we might behave when using a candy vending machine compared with a Las Vegas slot machine. When we use a vend- ing machine, prior experience has taught us that every time we put in the appropriate amount of money, the reinforcement, a candy bar, ought to be delivered. In other words, the schedule of

Schedules of reinforcement Different patterns of frequency and timing of reinforcement following desired behavior.

Continuous reinforcement schedule Reinforcing of a behavior every time it occurs.

Partial (or intermittent) reinforcement schedule Reinforcing of a behavior some but not all of the time.

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174 Chapter 5 LEARNING

Module 16 OPERANT CONDITIONING 175

reinforcement is continuous. In comparison, a slot machine offers intermittent reinforcement. We have learned that after putting in our cash, most of the time we will not receive anything in return. At the same time, though, we know that we will occasionally win something.

Now suppose that, unknown to us, both the candy vending machine and the slot machine are broken, and so neither one is able to dispense anything. It would not be very long before we stopped depositing coins into the broken candy machine. Probably at most we would try only two or three times before leaving the machine in disgust. But the story would be quite different with the broken slot machine. Here, we would drop in money for a considerably longer time, even though there would be no payoff.

In formal terms, we can see the difference between the two reinforcement schedules: partial reinforcement schedules (such as those provided by slot machines) maintain performance longer than do continuous reinforcement schedules (such as those established in candy vending machines) before extinction-the disappearance of the conditioned response-occurs.

Certain kinds of partial reinforcement schedules produce stronger and lengthier responding before extinction than do others. Although many dif- ferent partial reinforcement schedules have been examined, they can most readily be put into two categories: schedules that consider the number of responses made before reinforcement is given, called fixed-ratio and variable- ratio schedules, and those that consider the amount of time that elapses before reinforcement is provided, called fixed-interval and variable-interval schedules (Svartdal, 2003; Pellegrini et al., 2004; Gottlieb, 2006).

Fixed- and Variable-Ratio Schedules In a fixed-ratio schedule, reinforcement is given only after a specific number of responses. For instance, a rat might receive a food pellet every 10th time it pressed a lever; here, the ratio would be 1:10. Similarly, garment workers are generally paid on fixed-ratio schedules: they receive a specific number of dollars for every blouse they sew. Because a greater rate of production means more reinforcement, people on fixed-ratio schedules are apt to work as quickly as possible (see Figure 3).

In a variable-ratio schedule, reinforcement occurs after a varying num- ber of responses rather than after a fixed number. Although the specific number of responses necessary to receive reinforcement varies, the number of responses usually hovers around a specific average. A good example of a variable-ratio schedule is a telephone salespersoris job. She might make a sale during the third, eighth, ninth, and twentieth calls without being successful during any call in between. Although the number of responses that must be made before making a sale varies, it averages out to a 20 percent success rate. Under these circumstances, you might expect that the salesperson would try to make as many calls as possible in as short a time as possible. This is the case with all variable-ratio schedules, which lead to a high rate of response and resis- tance to extinction.

Fixed- and Variable-Interval Schedules: The Passage of Time In contrast to fixed- and variable-ratio schedules, in which the crucial factor is the number of responses, fixed-interval and variable-interval schedules focus on the amount of time that has elapsed since a person or animal was rewarded.

STUDY ALERT Remember that the different

schedules of reinforcement affect the rapidity with

which a response is learned and how long it

lasts after reinforcement is no longer provided.

Fixed-ratio schedule Aschedule by which reinforcement is given only after a specific number of responses are made. Variable-ratio schedule Aschedule by which reinforcement occurs after a varying number of responses rather than after a fixed number.

Fixed-Ratio Schedule

There are short pauses after each response

Variable-Ratio Schedule

e Time 4) Variable-Interval Schedule

FIGU E 3 Typical outcomes of different reinforcement schedules. (A) In a fixed- ratio schedule, short pauses occur after each response. Because the more responses, the more reinforcement, fixed-ratio schedules produce a high rate of responding. (B)In a variable-ratio schedule, responding also occurs at a high rate. (C)A fixed- interval schedule produces lower rates of responding, especially just after reinforcement has been presented, because the organism learns that a specified time period must elapse between reinforcements. (D)A variable-interval schedule produces a fairly steady stream of responses.

Fixed-Interval Schedule

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One example of a fixed-interval schedule is a weekly paycheck. For people who receive regular, weekly paychecks, it typically makes relatively little difference exactly how much they produce in a given week.

Because a fixed-interval schedule provides reinforcement for a response only if a fixed time period has elapsed, overall rates of response are rela- tively low. This is especially true in the period just after reinforcement, when the time before another reinforcement is relatively great. Students' study habits often exemplify this reality. If the periods between exams are relatively long (meaning that the opportunity for reinforcement for good performance is given fairly infrequently), students often study minimally

or not at all until the day of the exam draws near. Just before the exam, how- ever, students begin to cram for it, signaling a rapid increase in the rate of their

Fixed-interval schedule A schedule that provides reinforcement for a response only if a fixed time period has elapsed, making overall rates of response relatively low.

176 Chapter 5 LEARNING

There are typically long pauses after each response

Time

~.rT,ri· ng response. As you might expect, immediately after the exam there is _ _ _id decline in the rate of responding, with few people opening a book the

after a test. Fixed-interval schedules produce the kind of "scalloping --. " shown in Figure 3.

One way to decrease the delay in responding that occurs just after rein- : _ ement, and to maintain the desired behavior more consistently through-

an interval, is to use a variable-interval schedule. In a variable-interval - edule, the time between reinforcements varies around .some average '

er than being fixed. For example, a professor who gives surprise quiz- that vary from one every three days to one every three weeks, averaging

e every two weeks, is using a variable-interval schedule. Compared to the __ dy habits we observed with a fixed-interval schedule, students' study hab-

- under such a variable-interval schedule would most likely be very differ- t. Students would be apt to study more regularly because they would never ow when the next surprise quiz was coming. Variable-interval schedules, in

general, are more likely to produce relatively steady rates of responding tha'n e fixed-interval schedules, with responses that take longer to extinguish after

reinforcement ends.

05 Shaping: Reinforcing What Doesn't Come Naturally Consider the difficulty of using operant conditioning to teach people to repair an automobile transmission. If you had to wait until they chanced to fix a transmission perfectly before you provided them with reinforce- ment, the Model T Ford might be back in style long before they mastered the repair process.

There are many complex behaviors, ranging from auto repair to zoo management, that we would not expect to occur naturally as part of any- one's spontaneous behavior. For such behaviors, for which there might otherwise be no opportunity to provide reinforcement (because the behavior would never occur in the first place), a procedure known as shaping is used. Shaping is the process of teaching a complex behavior by reward- ing closer and closer approximations of the desired behavior. In shaping, you start by reinforcing any behavior that is at all similar to the behavior you want the person to learn. Later, yo~ reinforce only responses that are closer to the behavior you ultimately want to teach. Finally, you reinforce only the desired response. Each step in shaping, then, moves only slightly beyond the previously learned behavior, permitting the person to link the new step to the behavior learned earlier. Shaping allows even lower animals to learn complex responses that would never occur naturally, ranging from lions jumping through hoops, dolphins rescuing divers lost at sea, or rodents finding hidden land mines.

Comparing Classical and Operant Conditioning We've considered classical conditioning and operant conditioning as two com- pletely different processes. And, as summarized in Figure 4, there are a number of key distinctions between the two forms of learning. For example, the key concept in classical conditioning is the association between stimuli, whereas in

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Schedules of Reinforcement

Variable-interval schedule A schedule by which the time between reinforcements varies around some average rather than being fixed. Shaping The process of teaching a complex behavior by rewarding closer and closer approximations of the desired behavior.

Module 16 OPERANT CONDITIONING 177

the case of, • • MA HO

When Cliff Richards took over as the new depart- ment manager, he discovered that the existing staff was unusually inefficient and unproductive. Cliff learned that the previous manager often criticized and chided staff members for every little mistake until many of the best people had left, and the rest felt demoralized.

Cliff resolved not to criticize or punish staff mem- bers unless it was absolutely necessary. instead, he frequently complimented them whenever they did a

good job. He set daily production goals for them, and every Friday afternoon he bought lunch for all staff members who met their goals every day that week. Moreover, Cliff randomly conducted spot checks on what staff members were doing, and ifhe found them hard at work, he gave them small rewards such as extra break time.

Within just three months, productivity in Cliff's department nearly doubled. it became the most effi- cient department in the company.

1. How did Cliff take advantage of principles of operant conditioning to modify his staff's behavior?

2. Why did Cliff's predecessor's strategy of punishing undesirable behavior not work very well? Even if punishment and reinforcement strategies were equally effective at controlling behavior, why would reinforcement remain preferable?

3. How did Cliff make use of partial reinforcement schedules? What kinds of schedules did he use?

o 4. How could Cliff use his technique to train his staff to complete a complex new task that they had never

done before?

5. How might Cliff make use of principles of cognitive learning theory to improve his staff's productivity even further?

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