The timing of schedule-induced behavior

Schedule-induced drinking (SID) is a case of learning in the absence of explicit response-reinforcer contingency, characterized by accumulative excessive drinking following successive intermittent food pellet deliveries. Two experiments with rats were conducted to examine whether it was possible to displace SID to later than the post-pellet moment within inter-food intervals. In Experiment 1, SID was established under a fixed time (FT) 30-s food schedule. This was followed by a phase in which unsignaled lick-contingent delays were enforced during the initial seconds of the inter-food interval. Subsequently, a second FT 30-s baseline was reintroduced, followed by a phase of signaled lick-contingent delays. Results indicated that lick-contingent delays were ineffective in displacing SID. Instead, the signal produced a marking effect that increased licking. In Experiment 2, during the acquisition phase, water access was restricted during the initial 5, 10, or 20 s of the inter-food interval, followed by an FT 30-s schedule with water available. In the second phase, only the FT 30-s schedule was implemented to determine if the onset of drinking had been displaced by prior experience. These two phases were then repeated. Results showed that SID occurred during water accessibility periods. Displacement of SID was achieved, demonstrating similarities between induced and more explicit operant behavior. The findings are discussed in terms of how timing might result from a combination of reinforcement and induction.