MOTIVATIONAL CONTROL OF GOAL-DIRECTED ACTION

The control of goal-directed, instrumental actions by primary motivati onal states, such as hunger and thirst, is mediated by two processes. The first is engaged by the Pavlovian association between contextual o r discriminative stimuli and the outcome or reinforcer presented durin g instrumental training. Such stimuli exert a motivational influence o n instrumental performance that depends upon the relevance of the asso ciated outcome to the current motivational state of the agent. Moreove r, the motivational effects of these stimuli operate in the absence of prior experience with the outcome under the relevant motivational sta te. 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, motiva tional states do not influence the instrumental process directly; rath er, the agent has to learn about the value of an outcome in a given mo tivational state by exposure to it while in that state. This incentive learning is similar in certain respects to the acquisition of ''cathe xes'' envisaged by Tolman(1949a, 1949b).