Behaviour of rats in multiple schedules of response-contingent and response-independent food presentation

Abstract

During Phase I, three rats were exposed to two-component multiple schedules of response-independent food presentation. Low rates of lever-pressing were observed, and response rates in one component did not increase when food presentation was withheld in the other component. During Phase II, the same rats were exposed to two-component multiple schedules of response-contingent reinforcement. Much higher rates of lever-pressing were observed. Moreover, when reinforcement was withheld in one component, response rates in the other component increased (positive contrast), and when reinforcement was reinstated in the changed component, response rates in the other component declined (negative contrast). During Phase III, when food was again delivered independently of responding, the response rates declined again to low levels. These results indicate that the occurrence of non-instrumental lever-pressing is not a prerequisite for the occurrence of behavioural contrast in the rat, and thus cast doubt on the general applicability of the autoshaping theory of behavioural contrast