Motivational control of goal-directed action

The control of goal-directed, instrumental actions by primary motivational states, such as hunger and thirst, is mediated by two processes . The first is engaged by the Pavlovian association between contextual or discriminative stimuli and the outcome or reinforcer presented during instrumental training . Such stimuli exert a motivational influence on instrumental performance that depends upon the relevance of the associated outcome to the current motivational state of the agent . Moreover, the motivational effects ofthese stimuli operate in the absence ofprior experience with the outcome under the relevant motivational state . The second, instrumental, process is mediated by knowledge of the contingency between the action and its outcome and controls the value assigned to this outcome . In contrast to the Pavlovian process, motivational states do not influence the instrumental process directly ; rather, the agent has to learn about the value of an outcome in a given motivational state by exposure to it while in that state . This incentive learning is similar in certain respects to the acquisition of "cathexes" envisaged by Tolman (1949a, 1949b) .