ANTICIPATORY CONTRAST IN RATS ON FREE-OPERANT MULTIPLE SCHEDULES

Rats were trained on free-operant multiple schedules in which two target components associated with identical schedules but different stimuli were followed either by periods of continuous reinforcement or by extinction. Higher response rates (anticipatory contrast) occurred in the targets preceding extinction when a single exposure to the target and its following schedule occurred each session. When several different cycles involving both target components were presented each session, anticipatory contrast did not occur. Intermediate conditions with two or four cycles/session produced small unreliable contrast effects. The results indicate that differences between previous studies using consummatory response procedures and those using free-operant procedures have been due to procedural differences and not to the type of response/reinforcers in the two preparations. © 1992.