Classical conditioning was defined by I. Pavlov (1911) in his research on the salivary reflex in dogs. He observed that if a neutral stimulus (NS) is paired with an unconditioned stimulus (UCS) so that they become ‘associated’, then the NS develops the same ability to evoke a response as the UCS. Thus the NS becomes a conditioned stimulus (CS) and the response becomes a conditioned response (CR). This type of conditioning occurs only in involuntary behaviours such as salivation, sweating, heart rate and other behaviours controlled by the autonomic nervous system, and such a conditioned response may therefore be known as a CONDITIONED REFLEX. Reinforcement is delivered regardless of response, as it precedes it and is typically also the UCS (food in the case of Pavlovs experiment).
Operant or instrumental conditioning was defined and extensively researched by B.F. Skinner (1953). It involves training voluntary responses as the reinforcement is only delivered after the response and is contingent upon the response. Learning or conditioning involves the development of an association or bond between a stimulus and a response by reinforcing responses when they occur. Because reinforcement follows response, respondent behaviour can be manipulated by varying when the reinforcement is given (schedules of reinforcement). Learning is more resistant to extinction if the schedule of reinforcement used in training is related to the responses and is unpredictable. An example of this is gambling on a fruit machine. Extinction is the fading and disappearance of behaviour through non-reinforcement, e.g. socially unacceptable behaviour should be disregarded and not reinforced. Behaviour can be shaped towards a desirable end by the reinforcement of successive approximations to this. In this way, animals can be taught to do ‘tricks’ which would not be found in their normal repertoire of behaviour. Shaping principles underlie much of the control we exert over each other behaviour, especially childrens.