Conditioning

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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 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.