Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Psychology

Committee Chair

Michael Perone

Committee Co-Chair

Karen G Anderson

Committee Member

Michael Perone

Committee Member

Natalie J Shook

Abstract

Some problematic human behaviors can be conceptualized as choice of a large immediate reinforcer followed by a delayed aversive event, in lieu of a small immediate reinforcer and no delayed aversive event. For example, a night of binge drinking may result in ample social reinforcers and other fun in the short-term, but it is followed the next day by an intense hangover. Alternatively, opting for moderate alcohol consumption might not produce as intensely pleasing of an evening, but it avoids the aversive hangover. The aim of the present experiment was to develop an animal laboratory model for studying such choice situations. Rats could choose multiple pellets delivered immediately plus a delayed electric shock, or a single pellet delivered immediately. Using a titrating procedure, adjustments were made in the delay to shock based on the rat's choices. Exclusive choice of multiple pellets and shock decreased the delay in subsequent trials; exclusive choice of a single pellet increased the delay. Adjustments continued until the delay stabilized. The mean delay over the stable period was taken as an estimate of the indifference point -- the delay at which shock devalued multiple pellets to equal the value of 1 pellet. Indifference points were generated for different combinations of shock intensity and shock duration. Stable adjusting delay was an increasing function of shock intensity and shock duration. As shock was made more intense, it needed to be further delayed to obtain indifference. As shock was made to last longer, it also needed to be further delayed to obtain indifference. An analysis of response latency showed that when indifference points were obtained, latencies did not differ substantially between the two response types, consistent with the notion of indifference as equal value between alternatives. This procedure is a viable model of choice between a large immediate reinforcer followed by a delayed aversive event, versus a smaller immediate reinforcer. Possible refinements to the procedure are offered, and an interpretation is explored in terms of impulsivity.

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