Effect of delayed reinforcement on lever pressing for wheel-running reinforcement

Abstract

Delayed reinforcement can be understood as the interposition of a period of time between the occurrence of a behaviour and the delivery of a reinforcer. The present study investigated the effects of delayed reinforcement on the lever-pressing behaviour of eight Long-Evans rats for wheel running as reinforcement. Under the baseline condition, rats pressed a lever on a variable-ratio (VR) 5 schedule for the opportunity to run for 60 s as a reinforcement. Sessions terminated when 20 reinforcements were completed. Once baseline stabilized, delay durations of 2, 4, 8, 16 and 32 s were introduced over five consecutive sessions on three occasions under light change and no light change conditions. In the light change condition, the chamber lights were extinguished during wheel running. Results showed the lever-pressing rates did not decrease with delay in the light change condition, but they did in the no light change condition. Under both conditions, PRP duration and wheel-running rates increased with delay. The lack of a delay of reinforcement gradient in the no light change was attributed to the light change functioning as a conditioned reinforcement. These findings extend delay of reinforcement to wheel-running reinforcement.