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.