Self-imposed time-out by rats.

Abstract

Self-imposed time-out (TO) is a response that temporarily suspends a positive reinforcement schedule while altering associated environmental stimuli. This study tested competing hypotheses: whether TO functions as escape from the reinforcement contingency (Azrin, 1961) or is positively reinforced by stimulus changes (Appel, 1963). Sixteen male Wistar rats were divided into three groups and exposed to a two-lever chamber. Lever 1 (L1) delivered water under escalating fixed-ratio (FR) schedules (FR 5 to FR 40). Lever 2 (L2) produced (a) TO: Suspended L1 reinforcement and toggled chamber lighting; (b) EC: Changed lighting without suspending reinforcement; (c) CO: No consequences. A second L2 press restored original conditions for TO/EC groups. Results showed TO rats pressed L2 most frequently, with rates increasing alongside FR values. TO responses peaked immediately post-reinforcement, and L1 pressing nearly ceased during TO periods. Reinforcement rates were similar across all groups. EC rats showed minimal L2 use, undifferentiated by lighting, while CO rats rarely pressed L2. These findings strongly support Azrin's escape hypothesis, indicating that TO is maintained by negative reinforcement from aversive aspects of FR schedules. The results challenge traditional dichotomies between aversive and appetitive control, highlighting how positive reinforcement contingencies can acquire aversive properties that drive escape behavior.