Effect of Unsignaled Delay to Reinforcement on Within-Session Responding

Abstract

The present study determined if altering the unsignaled delay to reinforcement would alter the within-session pattern of responding. In both Experiments 1 and 2, 4 rats pressed a lever for reinforcers delivered by a variable-interval schedule during 50-min sessions. Across conditions, the value of the variable-interval schedule' was either 15 or 60 s and the unsignaled delay to reinforcement was 0.04, 0.20, 1.00, 5.00, or 25.00 s. Food-pellet reinforcers were delivered in Experiment 1 and 5% liquid-sucrose reinforcers were delivered in Experiment 2. Increasing the delay to reinforcement altered both response rates and response patterns, except when sucrose reinforcers were delivered by a variable interval 60-s schedule. These results may pose problems for some theories of delayed reinforcement. Perhaps more importantly, they indicate that procedural aspects can potentially influence conclusions made about the effect of delayed reinforcement. ,