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Thursday, December 2, 2010

Classical conditioning and motivational control

Classical conditioning and motivational control
For instance, a rat trained on an avoidance task, in which the sounding of a tone indicates that shock is likely, will, at least before the avoidance response has been fully learned, experience some pairings of the tone and the shock. As well as acquiring a response–outcome association, the rat can also be expected to form a tone–shock association. In other words, classical conditioning will occur, as a sort of by-product of the instrumental training procedure. This Pavlovian (S–S) association, it has been suggested, is responsible for energizing instrumental responding. By virtue of the S–S link, the tone will be able to activate the shock representation, producing in the animal both an expectation of shock and the set of emotional responses that we call fear. The state of fear is presumed to have motivational properties, so that the presentation of the tone could effectively boost the supply of energy that causes the animal to behave. The expectation evoked by the tone also gives value to the outcome. In av oidance learning, the outcome associated with the response is the absence of an event (the omission of shock). The absence of an event would not normally be reinforcing in itself, but it could certainly become so given the expectation that something unpleasant is likely to occur. This account of avoidance learning is a version of twoprocess theory, [two-process theory emphasizes the interaction of instrumental and classical conditioning processes in producing many types of behaviour] so called because it acknowledges that classical and instrumental learning processes both play a part in determining this type of behaviour. Although the theory was first elaborated in the context of avoidance learning, there is no reason to suppose that it applies only to this procedure. We have already seen how classical conditioning might contribute to the response suppression generated by the punishment procedure. In the appetitive case, stimuli present when an animal earns food by performing an instrumental response can be expected to become associated with the food. These stimuli will then be able to evoke a positive state (an ‘expectation of food’, a ‘state of hopefulness’) that parallels the negative, fearful, state produced in aversive training procedures.

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