Stimulus control of within-session variability and stereotypy of operant behavior in rats

Operant behavior customarily becomes very efficient or stereotyped after several sessions of exposure to a given response-reinforcement contingency. Operant behavior becomes very variable when a contingency is changed or behavior placed under extinction. These processes are usually studied separately. In our experiment we examined stimulus control of both processes within daily sessions. Each of six different responses produced 10 food reinforcers simultaneously with the “beep” from the feeder (CRF). The response reinforced in a given block of CRF was randomly determined. Therefore, each block of CRF was followed by a period of non-reinforcement until the rat emitted the response reinforced in the next block. Rats continued stereotyped responding when responses were followed by a beep, but immediately began to vary among the responses when there was no beep following a response, after 10 reinforcers. The results have implications for applied work that involves use of continuous reinforcement for different behaviors.