Immediate postsession feeding reduces operant responding in rats.

Three experiments investigated the effects of immediate and delayed postsession feeding on progressive-ratio and variable-interval schedule performance in rats. During Experiments 1 and 2, immediate postsession feeding decreased the breakpoint, or largest completed ratio, under progressive-ratio schedules. Experiment 3 was conducted to extend the results of the first two experiments to responding maintained by variable-interval schedules with different session lengths (15 and 60 min). Response rates decreased in all 4 subjects when postsession feeding immediately followed a 15-min session and in 3 of 4 subjects when postsession feeding immediately followed a 60-min session. The implications of this research are twofold: (1) The functional context in which within-session reinforcers are embedded extends outside the experimental chamber, and (2) supplemental postsession feedings should be sufficiently delayed from the end of a session to avoid weakening operant behavior in the experimental sessions.