The opponent-process theory of motivation: VIII. Quantitative and qualitative manipulations of food both modulate adjunctive behavior

The present studies extend the opponent-process theory of acquired motivation to the schedule-induced polydipsia paradigm and more generally to adjunctive behavior. The theory suggests that manipulations of the quality and the size of the pellet presented on an intermittent schedule should be important modulators of polydipsia. In Experiment 1, presenting animals with preferred, less preferred, or least preferred food pellets on a fixed-time 120-sec schedule resulted in progressively lower levels of water intake. In Experiment 2, the quality and size of the pellet were manipulated factorially. These variables were found to interact in the control of both the development and maintenance of schedule-induced drinking. Thus, predictions from the opponent-process theory were supported by these findings.