EFFECTS OF FIXED-INTERVAL SCHEDULE AND REINFORCER DURATION ON RESPONDING REINFORCED BY THE OPPORTUNITY TO RUN

Two experiments investigated the effects of schedule value and reinfor cer duration on responding for the opportunity to run on fixed-interva l (FI) schedules in rats. In the first experiment, 8 male Wistar rats were exposed to FI 15-s, 30-s, and 60-s schedules of wheel-running rei nforcement. The operant was lever pressing, and the consequence was th e opportunity to run for 60 s. In the second experiment, 8 male Long-E vans rats were exposed to reinforcer durations of 15 s, 30 s, and 90 s . The schedule of reinforcement was an FI 60-s schedule. Results showe d that postreinforcement pause and wheel-running rates varied systemat ically with reinforcer duration but not schedule value. Local lever-pr essing rates decreased with reinforcer duration. Overall lever-pressin g rates decreased with reinforcer duration but increased with schedule value. Although the reinforcer-duration effect is consistent with pre vious research, the lack a schedule effect appears to be the result of long postreinforcement pauses following wheel-running reinforcement t hat render the manipulation of the interval requirement ineffective.