Effect on subsequent fixed-interval schedule performance of prior exposure to ratio and interval schedules of reinforcement.

In three experiments, we examined the effect on the patterns of responding noted on fixed interval (FI) schedules of prior exposure to a range of interval and ratio schedules. Rats leverpressed for food reinforcement on random ratio (RR), random interval (RI), or variable interval (VI) schedules prior to transfer to FI schedules. In Experiment 1, prior exposure to an RR schedule retarded the development of typical FI patterns of responding. Exposure to a yoked RI schedule produced even greater retardation of typical FI performance. This effect was replicated in Experiment 2, using a within-subjects design. Rats responded on a multiple RR-RI schedule prior to a multiple FI-FI schedule. Typical FI performance emerged more slowly in the component previously associated with the RI than with that associated with the RR. In Experiment 3, exposure to an RR schedule retarded the development of FI performance to a greater extent than did exposure to a VR schedule. The latter schedule was programmed to allow the possibility that inhibitory control would develop after reinforcement. These results confirm that ratio schedules independently result in the disruption of FI responding. This effect was not long lasting and cannot be used plausibly to explain species differences in responding to FI schedules. However, it does suggest that temporal control--as manifested by the transfer of inhibitory control from one schedule to another--could facilitate movement between interval schedules.