Mechanisms of resurgence of an extinguished instrumental behavior.

Four experiments examined "resurgence" of an instrumental behavior after extinction. All experiments involved three phases in which rats were (1) trained to press one lever for food reward, (2) trained to press a second lever while the first leverpress was extinguished, and (3) tested under conditions in which neither leverpress was rewarded. In each experiment, the first leverpress recovered (resurged) in Phase 3, when the second leverpress was extinguished. The results demonstrated that resurgence occurred when the schedules of reinforcement employed in Phases 1 and 2 yielded either an upshift, downshift, or no change in the rate of reward delivery between those phases. They also demonstrated that initial training on the first lever was required to observe a robust increase in pressing at test (resurgence is thus an associative effect). Resurgence was shown to occur over a wide variety of schedules of reinforcement in Phase 2 (including ratio, interval, and leverpress-independent schedules). Finally, the results do not support the view that resurgence occurs because response competition suppresses leverpressing of the first lever during extinction. Overall, they are consistent with the view that resurgence is a renewal effect in which extinction of an instrumental behavior is specific to the context provided by rewarded leverpressing during the extinction phase.