Conditioning

Historical roots

Classical and operant conditioning

Comparison

Current research/future developments

Resources

Conditioning is a term used in psychology to refer to two specific types of associative learning, as well as to the operant and classical conditioning procedures that produce that learning. Very generally, operant conditioning involves administering or withholding reinforcements based on the performance of a targeted response, and classical conditioning involves pairing a stimulus that naturally elicits a response with one that does not until the second stimulus elicits a response like the first. Both of these procedures enabled the scientific study of associative learning, or the forming of connections between two or more stimuli. The goal of conditioning research is to discover basic laws of learning and memory in animals and humans.

Historical roots

Theories of conditioning and learning have a number of historical roots within the philosophical doctrine of associationism. Associationism holds that simple associations between ideas are the basis of human thought and knowledge, and that complex ideas are combinations of these simple associations. Associationism can be traced as far back as Aristotle (384–322 BC), who proposed three factors—contrast, similarity, and contiguity, or nearness in space or time of occurrence—that determine if elements, things, or ideas will be associated together.

British associationist-empiricist philosophers of the 1700s and 1800s such as John Locke (1632–1704), David Hume (1711–1776), and John Stuart Mill (1806–1873), held that the two most fundamental mental operations are association and sensation. As empiricists, they believed all knowledge is based on sensory experience, and complex mental processes such as language, or ideas such as truth, are combinations of directly experienced ideas. This school of thought differs from nativist views, which generally stress inherited genetic influences on behavior and thought. According to these views, humans are born with certain abilities or predispositions that actively shape or limit incoming sensory experience. For example, Plato (c. 427–347 BC) believed humans were born with certain pre-formed ideas, as did Rene Descartes (1596–1650). Many contemporary psychologists believe people are born with certain skill-based potentials and capacities such as those involved in language. In the 1880s, German psychologist Hermann Ebbinghaus (1850– 1909) brought this philosophical doctrine within the realm of scientific study by creating experimental methods for testing learning and memory that were based on associationistic theory. Associationist ideas are also at the root of behaviorism, a highly influential school of thought in psychology that was begun by American psychologist John Broadus Watson (1878–1958) in the 1910s. In addition, conditioning experiments enabling the standardized investigation of associations formed not between ideas but between varying stimuli, and stimuli and responses, are also based on associationism.

Classical and operant conditioning

The systematic study of conditioning began with Russian physiologist Ivan Petrovich Pavlov (1849– 1936). Working in the late 1800s, Pavlov developed the general procedures and terminology for studying classical conditioning wherein he could reliably and objectively study the conditioning of reflexes to various environmental stimuli.

Pavlov initially used a procedure wherein every few minutes a hungry dog was given dry meat powder that was consistently paired with a bell tone. The meat powder always elicited salivation; after a few experimental trials, the bell tone alone was able to elicit salivation. In Pavlov’s terminology, the meat powder is an unconditional stimulus because it reliably or unconditionally led to salivation. The salivation caused by the meat powder is an unconditional response because it did not have to be trained or conditioned. The bell tone is a conditional stimulus because it was unable to elicit salivation until it had been conditioned to do so through repeated pairings with the unconditional stimulus. The salivation that eventually occurred to the conditional stimulus alone (the bell tone) is now called a conditional response. Conditional responses are distinctly different from unconditional responses even though they superficially cause the same behavior. Conditioning is said to have occurred when the conditional stimulus will reliably elicit the conditional response or when reflexive behaviors have come under the control of a novel stimulus.

In line with his physiological orientation, Pavlov interpreted his findings according to his hypotheses about brain functioning. He believed that organism responses are determined by the interaction of excitatory and inhibitory processes in the brain’s cerebral hemispheres.

There are a number of different classical conditioning experimental designs. Besides varying the nature of the unconditional stimulus, many involve varying the timing of the presentation of the stimuli. Another type of experiment involves training a subject to respond to one conditional stimulus and not to any other stimuli. When this occurs it is called discrimination.

American psychologist Edward Lee Thorndike (1874–1949) developed the general procedures for studying operant conditioning (also referred to as instrumental conditioning) in the late 1800s. Thorndike’s experimental procedure typically involved placing cats inside specially designed boxes from which they could escape and obtain food located outside only by performing a specific behavior such as pulling on a string. Thorndike timed how long it took individual cats to gain release from the box over a number of experimental trials and observed that the cats behaved aimlessly at first until they seemed to discover the correct response as if by accident. Over repeated trials, the cats began to quickly and economically execute the correct response within just seconds. It seemed the initially random behaviors leading to release had become strengthened or reinforced by their positive consequences. It was also found that responses decreased and might eventually cease altogether when the food reward or reinforcement was no longer given. This is called extinction.

In the 1930s and 1940s, American psychologist Burrhus Frederic (B. F.) Skinner (1904–1990) modified Thorndike’s procedures by, for instance, altering the box so that food could be delivered automatically. In this way the probability and rate of responding could be measured over long periods of time without needing to handle the animal. Initially, Skinner worked with rats, but he eventually altered the box for use with pigeons.

In these procedures the response being conditioned, pressing the lever, is called the operant because it operates on the environment. The food reward or any consequence that strengthens a behavior is termed a reinforcer of conditioning. In operant conditioning theory, behaviors cease or are maintained by their consequences for the organism (Thorndike’s Law of Effect).

In most operant conditioning experiments, a small number of subjects are observed over a long period of time, and the dependent variable is the response rate in a given period of time. In traditional operant conditioning theory, physiological or biological factors are not used to explain behavior as they are in traditional classical conditioning theory.

Variations in operant conditioning experimental designs involve the nature of the reinforcement and the timing or scheduling of the reinforcers with respect to the targeted response. Reinforcement is a term used to refer to the procedure of removing or presenting negative or positive reinforcers to maintain or increase the likelihood of a response. Negative reinforcers are stimuli whose removal, when made contingent upon a response, will increase the likelihood of that response. Negative reinforcers then are unpleasant in some way, and they can range from uncomfortable physical sensations or interpersonal situations to severe physical distress. Turning off one’s alarm clock can be seen as a negative reinforcer for getting out of bed, assuming one finds the alarm unpleasant. Positive reinforcers are stimuli that increase the likelihood of a response when its presentation is made contingent upon that response. Giving someone pizza for achieving good grades is using pizza as a positive reinforcer for the desired behavior of achieving good grades (assuming the individual likes pizza). Punishment involves using aversive stimuli to decrease the occurrence of a response.

Reinforcement schedules are the timing and patterning of reinforcement presentation with respect to the response. Reinforcement may be scheduled in numerous ways, and because the schedule can affect the behavior as much as the reinforcement itself, much research has looked at how various schedules affect targeted behaviors. Ratio and interval schedules are two types of schedules that have been studied extensively. In ratio schedules, reinforcers are presented based on the number of responses made. In interval schedules, reinforcements are presented based on the length of time between reinforcements. Thus the first response to occur after a given time interval from the last reinforcement will be reinforced.

Conditioning theory thrived from approximately the 1940s through the 1960s, and many psychologists viewed the learning theories based upon conditioning as one of psychology’s most important contributions to the understanding of behavior. Psychologists created numerous variations on the basic experimental designs and adapted them for use with humans as well.

Comparison

Operant and classical conditioning have many similarities but there are important differences in the nature of the response and of the reinforcement. In operant conditioning, the reinforcer’s presentation or withdrawal depends on performance of the targeted response, whereas in classical conditioning the reinforcement (the unconditional stimulus) occurs regardless of the organism’s response. Moreover, whereas the reinforcement in classical conditioning strengthens the association between the conditional and unconditional stimulus, the reinforcement in operant conditioning strengthens the response it was made contingent upon. In terms of the responses studied, classical conditioning almost exclusively focuses on reflexive types of behavior that the organism does not have much control over, whereas operant conditioning focuses on non-reflexive behaviors that the organism does have control over.

Whether the theoretical underlying conditioning processes are the same is still an open question that may ultimately be unresolvable. Some experimental evidence supports an important distinction in how associations are formed in the two types of conditioning. Two-process learning theories are those that see classical and operant conditioning processes as fundamentally different.

Current research/future developments

How findings from conditioning studies relate to learning is an important question. However, first, learning must be defined. Psychologists use the term learning in a slightly different way than it is used in everyday language. For most psychologists, learning at its most general is evidenced by changes in behavior due to experience. In traditional theories of conditioning, learning is seen in the strengthening of a conditional reflex and the creation of a new association between a stimulus and a response. Yet more recent and complex conditioning experiments indicate that conditioning involves more than the strengthening of stimulus-response connections or new reflexes. It seems conditioning may be more accurately described as a process through which the relationship between events or stimuli and the environment are learned about and behavior is then adjusted.

In addition, research comparing normal and developmentally challenged children, and older children and adults, suggests that people have language- or rule-based learning forms that are more efficient than associative learning, and these types of learning can easily override the conditioning process. In sum, conditioning and associative learning seem to explain only certain aspects of human learning and are now seen as simply another type of learning task. Therefore, while conditioning had a central place in American experimental psychology from approximately the 1940s through the 1960s, its theoretical importance for learning has diminished. On the other hand, practical applications of conditioning procedures and findings continue to grow.

See also Reinforcement, positive and negative.

Resources

BOOKS

Gallistel, C. R. The Symbolic Foundations of Conditioned Behavior. Mahwah, NJ: Erlbaum Associates, 2002.

Mazur, James E. Learning and Behavior. Upper Saddle River, NJ: Prentice Hall, 2001.

Schwartz, B. Psychology of Learning and Behavior. 5th ed. New York: W.W. Norton & Co., Inc., 2002.

Marie Doorey

Conditioning

Conditioning is a term used in psychology to refer to two specific types of associative learning as well as to the operant and classical conditioning procedures which produce that learning. Very generally, operant conditioning involves administering or withholding reinforcements based on the performance of a targeted response, and classical conditioning involves pairing a stimulus that naturally elicits a response with one that does not until the second stimulus elicits a response like the first. Both of these procedures enabled the scientific study of associative learning, or the forming of connections between two or more stimuli. The goal of conditioning research is to discover basic laws of learning and memory in animals and humans.

Historical roots

Theories of conditioning and learning have a number of historical roots within the philosophical doctrine of associationism. Associationism holds that simple associations between ideas are the basis of human thought and knowledge, and that complex ideas are combinations of these simple associations. Associationism can be traced as far back as Aristotle (384-322 b.c.), who proposed three factors—contrast, similarity, and contiguity, or nearness in space or time of occurrence—that determine if elements, things, or ideas will be associated together.

British associationist-empiricist philosophers of the 1700s and 1800s such as Locke, Hume, and Mills, held that the two most fundamental mental operations are association and sensation. As empiricists, they believed all knowledge is based on sensory experience, and complex mental processes such as language, or ideas such as truth, are combinations of directly experienced ideas. This school of thought differs from nativist views which generally stress inherited genetic influences on behavior and thought. According to these views, we are born with certain abilities or predispositions that actively shape or limit incoming sensory experience. For example, Plato (c. 427–347 b.c.) believed we are born with certain pre-formed ideas as did Rene Descartes (1596-1650). Many contemporary psychologists believe we are born with certain skill-based potentials and capacities such as those involved in language. In the 1880s the German psychologist Hermann Ebbinghaus brought this philosophical doctrine within the realm of scientific study by creating experimental methods for testing learning and memory that were based on associationistic theory. Associationist ideas are also at the root of behaviorism, a highly influential school of thought in psychology that was begun by John B. Watson in the 1910s. And conditioning experiments enabling the standardized investigation of associations formed, not between ideas, but between varying stimuli, and stimuli and responses, are also based on associationism.

Classical and operant conditioning

The systematic study of conditioning began with the Russian physiologist Ivan P. Pavlov. Working in the late 1800s, Pavlov developed the general procedures and terminology for studying classical conditioning wherein he could reliably and objectively study the conditioning of reflexes to various environmental stimuli.

Pavlov initially used a procedure wherein every few minutes a hungry dog was given dry meat powder that was consistently paired with a bell tone. The meat powder always elicited salivation, and after a few experimental trials the bell tone alone was able to elicit salivation. In Pavlov's terminology, the meat powder is an unconditional stimulus because it reliably or unconditionally led to salivation. The salivation caused by the meat powder is an unconditional response because it did not have to be trained or conditioned. The bell tone is a conditional stimulus because it was unable to elicit salivation until it had been conditioned to do so through repeated pairings with the unconditional stimulus. The salivation that eventually occurred to the conditional stimulus alone (the bell tone) is now called a conditional response. Conditional responses are distinctly different from unconditional responses even though they are superficially the same behavior. Conditioning is said to have occurred when the conditional stimulus will reliably elicit the conditional response, or when reflexive behaviors have come under the control of a novel stimulus.

In line with his physiological orientation, Pavlov interpreted his findings according to his hypotheses about brain functioning. He believed that organism responses are determined by the interaction of excitatory and inhibitory processes in the brain's cerebral hemispheres.

There are a number of different classical conditioning experimental designs. Besides varying the nature of the unconditional stimulus, many involve varying the timing of the presentation of the stimuli. Another type of experiment involves training a subject to respond to one conditional stimulus and not to any other stimuli. When this occurs it is called discrimination.

American psychologist Edward L. Thorndike developed the general procedures for studying operant conditioning (also referred to as instrumental conditioning) in the late 1800s. Thorndike's experimental procedure typically involved placing cats inside specially designed boxes from which they could escape and obtain food located outside only by performing a specific behavior such as pulling on a string. Thorndike timed how long it took individual cats to gain release from the box over a number of experimental trials and observed that the cats behaved aimlessly at first until they seemed to discover the correct response as if by accident. Over repeated trials the cats began to quickly and economically execute the correct response within just seconds. It seemed the initially random behaviors leading to release had become strengthened or reinforced by their positive consequences. It was also found that responses decreased and might eventually cease altogether when the food reward or reinforcement was no longer given. This is called extinction .

In the 1930s and 1940s, the American psychologist Burrhus F. Skinner modified Thorndike's procedures by, for instance, altering the box so that food could be delivered automatically. In this way the probability and rate of responding could be measured over long periods of time without needing to handle the animal . Initially, Skinner worked with rats but he eventually altered the box for use with pigeons.

In these procedures the response being conditioned, pressing the lever, is called the operant because it operates on the environment. The food reward or any consequence that strengthens a behavior is termed a reinforcer of conditioning. In operant conditioning theory, behaviors cease or are maintained by their consequences for the organism (Thorndike's "Law of Effect").

In most operant conditioning experiments, a small number of subjects are observed over a long period of time, and the dependent variable is the response rate in a given period of time. In traditional operant conditioning theory, physiological or biological factors are not used to explain behavior as they are in traditional classical conditioning theory.

Variations in operant conditioning experimental designs involve the nature of the reinforcement and the timing or scheduling of the reinforcers with respect to the targeted response. Reinforcement is a term used to refer to the procedure of removing or presenting negative or positive reinforcers to maintain or increase the likelihood of a response. Negative reinforcers are stimuli whose removal, when made contingent upon a response, will increase the likelihood of that response. Negative reinforcers then are unpleasant in some way, and they can range from uncomfortable physical sensations or interpersonal situations, to severe physical distress. Turning off one's alarm clock can be seen as a negative reinforcer for getting out of bed, assuming one finds the alarm unpleasant. Positive reinforcers are stimuli that increase the likelihood of a response when its presentation is made contingent upon that response. Giving someone pizza for achieving good grades is using pizza as a positive reinforcer for the desired behavior of achieving good grades (assuming the individual likes pizza). Punishment involves using aversive stimuli to decrease the occurrence of a response.

Reinforcement schedules are the timing and patterning of reinforcement presentation with respect to the response. Reinforcement may be scheduled in numerous ways, and because the schedule can affect the behavior as much as the reinforcement itself, much research has looked at how various schedules affect targeted behaviors. Ratio and interval schedules are two types of schedules that have been studied extensively. In ratio schedules, reinforcers are presented based on the number of responses made. In interval schedules, reinforcements are presented based on the length of time between reinforcements. Thus the first response to occur after a given time interval from the last reinforcement will be reinforced.

Conditioning and theory thrived from approximately the 1940s through the 1960s, and many psychologists viewed the learning theories based upon conditioning as one of psychology's most important contributions to the understanding of behavior. Psychologists created numerous variations on the basic experimental designs and adapted them for use with humans as well.

Comparison

Operant and classical conditioning have many similarities but there are important differences in the nature of the response and of the reinforcement. In operant conditioning, the reinforcer's presentation or withdrawal depends on performance of the targeted response, whereas in classical conditioning the reinforcement (the unconditional stimulus) occurs regardless of the organism's response. Moreover, whereas the reinforcement in classical conditioning strengthens the association between the conditional and unconditional stimulus, the reinforcement in operant conditioning strengthens the response it was made contingent upon. In terms of the responses studied, classical conditioning almost exclusively focuses on reflexive types of behavior that the organism does not have much control over, whereas operant conditioning focuses on non-reflexive behaviors that the organism does have control over.

Whether the theoretical underlying conditioning processes are the same is still an open question that may ultimately be unresolvable. Some experimental evidence supports an important distinction in how associations are formed in the two types of conditioning. Two-process learning theories are those that see classical and operant conditioning processes as fundamentally different.

Current research/future developments

How findings from conditioning studies relate to learning is an important question. But first we must define learning. Psychologists use the term learning in a slightly different way than it is used in everyday language. For most psychologists, learning at its most general is evidenced by changes in behavior due to experience. In traditional theories of conditioning learning is seen in the strengthening of a conditional reflex , and the creation of a new association between a stimulus and a response. Yet more recent and complex conditioning experiments indicate that conditioning involves more than the strengthening of stimulus-response connections or new reflexes. It seems conditioning may be more accurately described as a process through which the relationship between events or stimuli and the environment are learned about and behavior is then adjusted.

In addition, research comparing normal and retarded children, and older children and adults, suggests that people have language- or rule-based learning forms that are more efficient than associative learning, and these types of learning can easily override the conditioning process. In sum, conditioning and associative learning seem to explain only certain aspects of human learning, and are now seen as simply another type of learning task. So, while conditioning had a central place in American experimental psychology from approximately the 1940s through the 1960s, its theoretical importance for learning has diminished. On the other hand, practical applications of conditioning procedures and findings continue to grow.

See also Reinforcement, positive and negative.

Resources

books

Hearst, E. "Fundamentals of Learning and Conditioning." Stevens' Handbook of Experimental Psychology. 2nd ed. Edited by R.C. Atkinson, R.J. Herrnstein, G. Lindzey, and R. D. Luce. New York: John Wiley & Sons, 1988.

Mackintosh, N.J. "Classical and Operant Conditioning." In Companion Encyclopedia of Psychology, ed. A. W. Colman. New York: Routledge, 1994.

Schwartz, B. Psychology of Learning and Behavior. 3rd ed. New York: W.W. Norton & Co., Inc., 1988.

Marie Doorey

KEY TERMS

Associationism

—A philosophical doctrine which holds that simple associations between ideas are the basis of all human thought and knowledge, and complex ideas are built upon combinations of the simple.

Behaviorism

—A highly influential school of thought in psychology, it holds that observable behaviors are the only appropriate subject matter for psychological research.

Classical conditioning

—A procedure involving pairing a stimulus that naturally elicits a response with one that does not until the second stimulus elicits a response like the first.

Conditional

—Term used in classical conditioning to describe responses that have been conditioned to elicit certain responses. It also describes the stimuli that elicit such responses

Empiricism

—A general philosophical position holding that all knowledge comes from experience, and that humans are not born with any ideas or concepts independent of personal experience.

Operant conditioning

—A procedure involving administering or withholding reinforcements based on the performance, or partial performance, of a targeted response.

Unconditional

—Term used in classical conditioning to describe responses that are naturally or unconditionally elicited, they do not need to be conditioned. It also describes the stimuli that elicit such responses.

Conditioning

A broad term to describe techniques used by psychologists to study the process of learning.

Psychology has often been defined as the study of behavior. As such, psychologists have developed a diverse array of methods for studying both human and animal activity. Two of the most commonly used techniques are classical conditioning and operant conditioning . They have been used to study the process of learning, one of the key areas of interest to psychologists in the early days of psychology. Psychologists also attach considerable significance to conditioning because it has been effective in changing human and animal behavior in predictable and desirable ways.

The Russian physiologist Ivan Pavlov developed the principles of classical conditioning. In his Nobel Prize-winning research on the digestive processes, he placed meat powder in the mouths of his research animals and recorded their levels of salivation. At one point,

he noticed that some of his research animals began to salivate in the absence of food. He reasoned that the presence of the animal caretakers led the animals to anticipate the meat powder, so they began to salivate even without the food.

When classical conditioning occurs, an animal or person initially responds to a naturally occurring stimulus with a natural response (e.g., the food leads to salivation). Then the food is systematically paired with a previously neutral stimulus (e.g., a bell), one that does not lead to any particular response. With repeated pairings, the natural response occurs when the neutral stimulus appears.

Pavlovian (i.e., classical) conditioning influenced psychologists greatly, even though Pavlov himself was skeptical of the work psychologists performed. In the United States, John Watson , the first widely known behaviorist, used the principles of classical conditioning in his research. For example, in a widely cited study, Watson tried to develop a classically conditioned phobia in an infant.

Although classical conditioning became the dominant Russian model for the study of behaviorism , another form of conditioning took hold in the United States. This version, which became known as operant or instrumental conditioning, initially developed from the ideas of the psychologist Edward Thorndike . Thorndike began his psychological research by studying learning in chickens, then in cats. Based on the problem solving of these animals, he developed the Law of Effect , which in simple form states that a behavior that has a positive outcome is likely to be repeated. Similarly, his Law of Exercise states that the more a response occurs in a given situation, the more strongly it is linked with that situation, and the more likely it is to be repeated in the future.

Operant conditioning was popularized by the psychologist B.F. Skinner . His research and writings influenced not only psychologists but also the general public. Operant conditioning differs from classical conditioning in that, whereas classical conditioning relies on an organism's response to some stimulus in the environment , operant conditioning relies on the organism's initiating an action that is followed by some consequence.

For example, when a hungry person puts money into a vending machine, he or she is rewarded with some product. In psychologists' terms, the behavior is reinforced; in everyday language, the person is satisfied with the outcome. As a result, the next time the person is hungry, he or she is likely to repeat the behavior of putting money into the machine. On the other hand, if the machine malfunctions and the person gets no food, that individual is less likely to repeat the behavior in the future. This refers to punishment .

Any time a behavior leads to a positive outcome that is likely to be repeated, psychologists say that behavior has been reinforced. When the behavior leads to a negative outcome, psychologists refer to it as punishment. Two types of reinforcement and punishment have been described: positive and negative.

Positive reinforcement is generally regarded as synonymous with reward: when a behavior appears, something positive results. This leads to a greater likelihood that the behavior will recur. Negative reinforcement involves the termination of an unpleasant situation. Thus, if a person has a headache, taking some kind of pain reliever leads to a satisfying outcome. In the future, when the person has a headache, he or she is likely to take that pain reliever again. In positive and negative reinforcement, some behavior is likely to recur either because something positive results or something unpleasant stops.

Just as reinforcement comes in two versions, punishment takes two forms. Psychologists have identified positive punishment as the presentation of an unpleasant result when an undesired behavior occurs. On the other hand, when something positive is removed, this is called negative punishment. In both forms of punishment, an undesired behavior results in a negative consequence. As a result, the undesired behavior is less likely to recur in the future.

Many people mistakenly equate negative reinforcement with punishment because the word "negative" conjures up the idea of punishment. In reality, a situation involving negative reinforcement involves the removal of a negative stimulus, leading to a more satisfying situation. A situation involving punishment always leads to an unwanted outcome.

Beginning with Watson and Skinner, psychology in the United States adopted a behavioral framework in which researchers began to study people and animals through conditioning. From the 1920s through the 1960s, many psychologists performed conditioning experiments with animals with the idea that what was true for animals would also be true for humans. Psychologists assumed that the principles of conditioning were universal. Although many of the principles of learning and conditioning developed in animal research pertain to human learning and conditioning, psychologists now realize that each species has its own behavioral characteristics. Consequently, although the principles of conditioning may generalize from animals to humans, researchers must consider the differences across species as well.

See also Aversive conditioning; Classical conditioning; Operant conditioning

Further Reading

Mackintosh, N. J. Conditioning and Associative Learning. New York: Oxford University Press, 1983.

Walker, James T. The Psychology of Learning. Upper Saddle River, NJ: Prentice-Hall, 1996.

conditioning My heart races and my palms sweat during my first attempt to drive again after a traumatic road accident. Alternatively, having discovered that a new joke goes down well at work, I find myself retelling it ad nauseam. These two scenarios are examples of different forms of conditioning. The first is an example of classical conditioning, and involves learning about the predictive relationship between stimuli. As a result of the car accident, the interior of a car, let alone the touch of steering wheel, has become a signal for a traumatic event and thereby elicits a fear reaction through the activation of my autonomic nervous system. By contrast, my new found humour is an example of ‘instrumental’ or ‘operant’ conditioning. In this case, I have learned about the causal relationship between an action, the telling of the joke, and the apparent attention and interest that it elicits in my friends and colleagues, which only serves to reward this tedious behaviour.

Classical conditioning is often referred to as ‘Pavlovian’ because this form of learning was discovered by the renowned Russian physiologist, Pavlov, in his experiments on the neural control of digestion at the end of the nineteenth century. As is well known, Pavlov signalled the presentation of food to his hungry dogs by turning on a stimulus, such a bell, some seconds before the delivery of each meal. Although the bell initially produced little more than orientation towards its source, after a number of pairings with the food this stimulus began to elicit novel behaviour. As soon as the signal came on, the dogs approached the location of the food and started salivating copiously. The occurrence of the responses depended, or were conditional, upon experience of the predictive relationship between the signal and the food, and thus came to be known as ‘conditioned’. Correspondingly, the signal is called a conditioned stimulus, because its property also depends upon learning about the predictive relationship. By contrast, the food is an unconditioned stimulus, because the salivation that it elicits, the unconditioned response, does not depend upon the learning experience. Pavlov also referred to the food as a reinforcer, as it is the event responsible for strengthening the conditioned response. Although it was originally thought that simple pairings of a conditioned stimulus and a reinforcer are sufficient for conditioning, we now know that only signals that are informative about the occurrence of the reinforcer become conditioned. Moreover, conditioning is not always a simple, automatic and non-conscious process and, in certain cases, only occurs in humans when they are already aware of the relationship between signal and reinforcer.

The salivation elicited by the signals for food is an appetitive conditioned response because the reinforcer, the food, is attractive. By contrast, my hypothetical fear response to the car is an example of aversive or defensive conditioning, because the reinforcer in this case, the accident, is noxious and distressing. Pavlovian conditioning affects a gamut of response and behaviour systems, from the sexual evaluation of members of the opposite sex to food preference and aversions. Moreover, this form of conditioning also plays a role not only in behavioural responses but also in the regulatory systems of the body. For example, if drinking a fluid with a particular flavour signals an infusion of glucose into the stomach of hungry rats, that flavour will, in future, reduce blood sugar level in anticipation of the glucose load.

The experimental study of ‘instrumental’ conditioning also started over 100 years ago, but in this case by an American comparative psychologist, Thorndike, who was interested in comparing the learning capacities of different species of animal. Thorndike studied the rate at which a variety of animals learned to operate a latch in order to escape from a cage to eat some food placed outside. These instrumental tasks were subsequently refined over the succeeding decades, most notably by the behaviourist psychologist, Skinner. As in the case of Pavlovian conditioning, the food acted as a reinforcer to strengthen the conditioned response, the operation of the latch, but in the instrumental case through a positive causal relationship between the response and reinforcer. In contrast to Pavlovian conditioning, however, aversive or noxious stimuli cannot act as instrumental reinforcers through a positive relationship with a response. Indeed, when a response causes an aversive outcome, the behaviour is suppressed or punished. For an aversive event, such as a road accident, to reinforce the appropriate instrumental response (careful and defensive driving) the response has to prevent the event happening and thereby allow us to escape or avoid dangerous and unpleasant situations.

There are two sorts of learning process underlying instrumental conditioning. The first process establishes response habits through the acquisition of a connection between an eliciting stimulus and the response. For example, enhancement of the limb muscle reflexes involved in the movements that the rat must make to reach for the latch can be conditioned by arranging for an appropriate change to be reinforced by the delivery of food to a hungry animal. This simple stimulus–response development clearly plays a role in the acquisition of motor skills. Other learning processes are involved in more complex forms of instrumental conditioning, which support goal-directed actions based upon knowledge of the causal relationship between the action and the outcome that it achieves. This type of instrumental conditioning operates when one explicitly plans a course of action to achieve a specific goal.

In summary, the two forms of conditioning, Pavlovian and instrumental, reflect the processes by which we and other animals learn to adjust our behaviour to the predictive and causal structure of our environment. The fact that, in one form or another, both types of conditioning are to be found throughout the animal kingdom, from relatively simple invertebrates to ourselves, is a testimony to their ubiquitous and important adaptive function.

A. Dickinson

Bibliography

Dworkin, B. R. (1993). Learning and physiological regulation. The University of Chicago Press, Chicago.
Mackintosh, N. J. (1983). Conditioning and associative learning. Oxford University Press, New York.

conditioning A term employed by behaviourist psychologists within the framework of stimulus-response (S–R) models of learning. It refers to the process whereby new stimulus-response connections are established.

Behaviourists conventionally distinguish two types of conditioning. In classical or Type-S conditioning, first identified by Ivan Pavlov in his famous experiments with dogs, a new stimulus is linked to an already existing response. The new S–R connection is established by contiguously pairing the new, formerly neutral, stimulus with an old one which already provokes the response. In Pavlov's experiments, the old, unconditioned (or unconditional) response (UCS) of food in the mouth provokes a reflex unconditioned (unconditional) response (UCR). When this stimulus is repeatedly paired with a new one (the sound of a bell) this new stimulus will, in time, produce salivation. A new connection is, therefore, established between a conditioned (conditional) stimulus (CS), the sound of the bell, and a conditioned response (CR), salivation. In this process, the pairing of food with the sound of the bell serves to strengthen or reinforce the new S–R connection—that is, to make the occurrence of the response of salivation to the sound of the bell more likely. Frequent repetition of the new stimulus without reinforcement (food) leads to extinction of the conditioned response.

In operant, instrumental, or Type-R conditioning, a new response is established to a formerly neutral stimulus. This response is encouraged by the introduction of some reinforcement of that response whenever it occurs. The approach is commonly associated with the American psychologists E. L. Thorndike (Animal Intelligence, 1911) and B. F. Skinner (The Behaviour of Organisms, 1938). In Skinner's well-known experiments with rats in cages, the pressing of a bar is reinforced by giving a pellet of food (the reinforcing stimulus) whenever the bar is pressed. Reinforcement utilizing pleasure is termed positive reinforcement. Where the reinforcement takes the form of avoiding something that is unpleasant (an electric shock, a disagreeable taste) it is termed negative reinforcement. Where a reinforcer derives its value through learning it is termed a secondary reinforcer. For example, if a rat learns to obtain tokens to secure food, the tokens may be used as secondary reinforcers in conditioning some new response. Operant conditioning has also been used as a basis of therapy for humans. Subjects learn that certain patterns of behaviour have desirable consequences, that is they are rewarded, and this increases the likelihood of the behaviour occurring in the future.

Much of the debate amongst learning theorists has concerned the interpretation of the empirical observations made in studies of conditioning. Early behaviourists developed analyses of conditioning that suggested it was a simple, unconscious, and automatic process. However, a number of experiments provided convincing evidence that cognitive processes were involved in establishing the stimulus-response connections observed in conditioning studies. In academic psychology from the 1960s onwards, the increasing emphasis on cognition and information processing has shifted attention away from studies of conditioning in animals and humans, and from conceptualizing learning in terms of stimulus-response models.