Title: THE EFFECTS OF DELAYED REINFORCEMENT AND A RESPONSE-PRODUCED AUDITORY STIMULUS ON THE ACQUISITION OF OPERANT BEHAVIOR IN RATS

The present experiment examined the effects of different delays of food delivery with and without a response-produced auditory stimulus on the acquisition of a spatially defined operant in rats. The operant was breaking a photoelectric beam located near the ceiling at the rear of the experimental chamber. In five groups of experimentally naive rats, the effects on photobeam-break responses of two different reinforcement delays (4 s and 10 s) with and without a response-produced auditory stimulus were compared during eight 1-hr sessions. In one control group (0-s delay), an immediate (i.e., 0.25-s) reinforcement contingency was in effect and in another control group (no food), responses were measured in the absence of any reinforcement contingencies. Results showed that rates of acquisition and responding were higher with shorter reinforcement delays and when there was a response-produced auditory stimulus. These results extend previous findings showing that neither direct shaping nor immediate reinforcement is necessary for operant conditioning. However, the present results demonstrate that the speed and extent of conditioning depends on the temporal relation between the response and the reinforcer. The findings are discussed in terms of a conditioned reinforcement analysis of the stimuli produced by operant responses.