The acquisition of lever-pressing by rats under degraded conditions of conditioned reinforcement

There are few studies on the acquisition of new responses under degraded conditions of conditioned reinforcement. In this investigation the establishment and subsequent maintenance of a new response was studied with 21 rats directly exposed to a constant random-interval 7.5 s schedule for a 1-s light stimulus for leverpressing. Concurrently, the same stimulus and one food pellet were delivered independently of responding across the entire 32-minute sessions on a fixed-time 64 s schedule. For three rats each the stimulus and the delivery of food were separated by intervals of either 0, 1, 2, 4, 8, 16, or 32 s over consecutive blocks of 40 sessions. Although at low rates all rats lever-pressed even with intervals between the stimulus and food as long as 32 s. Response rates were progressively lower as the stimulus-food interval was lengthened, resembling a gradient of efficacy of conditioned reinforcement. Such finding is new to the literature on theacquisition of new responses with conditioned reinforcement.