Variable Ratio Schedules of Reinforcement and Resistance to Extinction in Rats

Variable Ratio Schedules of Reinforcement and Resistance to Extinction in Rats

Scott Robertson

Boston University

May 1, 2009

Abstract

The effect of different levels of variable ratio (VR) schedules of reinforcement on bar pressing behavior in rats was examined. Thirty-two male Sprague-Dawley rats were trained to lever press on four different schedules of reinforcement using food pellet delivery as the reinforcement. The first group was placed on a continuous reinforcement (CRF) schedule. The second was placed on a variable ratio 5 schedule (reinforcement on average every 5 responses). The third group was placed on a variable ratio 25 schedule (reinforcement on average after 25 responses). The fourth group was placed on a variable ratio 50 schedule (reinforcement on average after 50 responses). Each group was then put through an extinction phase. The results revealed that the subjects on the partial reinforcement schedules took significantly longer to reach extinction and responded significantly more during extinction than the subjects on the CRF schedule. Extinction performance increased significantly as the value of the VR schedule was increased.

Variable Ratio Schedules of Reinforcement and Extinction Performance in Rats

Different schedules of reinforcement can significantly impact operant behavior in organisms. The choice of one schedule over another can determine the ultimate level of conditioning that occurs in training as well as how the organism will perform during extinction when reinforcement is withheld. Extinction performance is often the final goal of conditioning sessions and it is for that reason it is a subject of much interest in behavioral studies.

There are essentially two different major schedules of reinforcement used in operant conditioning. Continuous and partial reinforcement schedules. Continuous reinforcement (CRF) schedules provide reinforcement for every occurrence of a...