Negative S− contrast with minimal response requirements in S+

Abstract

DISCUSSIONResults of this study clearly indicate that a prior history of response contingent food-CR parings is not a necessary condition for establishing CR maintained responding in the Zimmerman and Hanford one-key procedure. It further demonstrates that response rates are comparable to previously reported studies and respond similarly to parametric manipulations. The two control conditions point out that the strength of the response was directly related to the specific stimuli paired with food since responding dropped dramatically when a novel stimulus was introduced and during CR extinction. The dramatic increase in response rates for two of the subjects following CR extinction is hard to explain. It possibly could be a result of the nature of the CR extinction condition, namely, allowing CR-food pairings to continue thus strengthening the reinforcing properties of the CR while not allowing for the concommitant reduction in CR strength because the CR was not presented without the food. Forty rats received runway and placement reward training in an experiment which factorialized, between subjects, the amount of runway and placement reward received on each trial. Speeds to the small runway reward were depressed by large reward placements and by a discrepancy between placement and runway reward amounts. The results suggest that the S--contrast effect observed in differential conditioning occurs even when S+ response requirements are minimal and quite different from those in S-. Bulletin of the PsychonomicSeveral differential instrumental conditioning studies have demonstrated that locomotor speeds to one cue (SI) are a function of the relationship between the reward magnitude contingent upon SI running and the reward magnitude contingent upon running to the other *Based in part on a thesis submitted by th e senior author to the Southern Illinois University Graduate School in partial fulfillment of the requirements for the M.A. degree. Reprint requests should be sent to James H. McHose, Department of Psychology, Southern Illinois University at Carbondale, Carbondale, Illinois 62901.tNow at Laurentian University, Sudbury, Ontario, Canada.25 cue (S2) (cf. McHose, 1970). More specifically the discrepancy between an S+ reward magnitude and an Sreward magnitude typically produces al -depression of both S+ and S-running speeds. The purpose of the present study was to determine whether this discrepancy between S+ and S-reward magnitudes produces a depression of S-speeds in the absence of an S+ instrumental running response. Maxwell, Meyer, Calef, and McHewitt (1969) and Calef (1972) employed standard runway S-trials, while the S+ trials consisted of placing the subjects directly at the