Semester

Fall

Date of Graduation

2023

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Psychology

Committee Chair

Michael Perone

Committee Member

Karen G. Anderson

Committee Member

Mariya Cherkasova

Committee Member

Eric Horstick

Committee Member

Andy Lattal

Abstract

In the context of choice, one is said to show self-control under numerous conditions in which consideration is given to the delayed outcomes of each option. This can be difficult: both reinforcing and aversive outcomes become less effective as they are increasingly delayed. Several socially significant issues arise from a failure of delayed, aversive outcomes to impact choice, especially when immediate, reinforcing outcomes are available. Identifying the conditions under which choice is sensitive to delayed outcomes is critical to shifting choices toward alternatives in which contact with delayed, aversive outcomes is minimized. Two experiments were conducted with the aim of charactering how preference for an outcome that includes immediate reinforcement and a delayed, aversive outcome changes as a function of the delay to the aversive outcome. In Experiment 1 a discrete-trial choice procedure was used. Rats chose, by pressing one of two levers, between two outcomes: a small reinforcer alone and a large reinforcer plus a delayed shock. The delay to shock was lowered each session and changes in choice were measured. Rats preferred the lever that produced the large reinforcer plus shock when the delay to shock was long; however, preference switched to the small reinforcer alone as the delay to shock was lowered each session. Acute effects of oxycodone and methylphenidate were assessed on this behavioral baseline. Oxycodone’s effects on choice depended on the dose: low doses produced a slight, and inconsistent, increase in choice of the large reinforcer plus shock and high doses produced a slight increase in choice the small reinforcer. Methylphenidate typically increased choice of the small reinforcer. In Experiment 2 a concurrent-chains procedure was used. Rats chose between two outcomes, both of which included a reinforcer and a delayed shock. Each outcome differed, however, in the relative delay to shock: one delay was short and the other was long. The relative delays to shock arranged as an outcome for pressing each lever was changed either within or across sessions. Choice was not sensitive to changes in the relative delays to shock: rats chose the levers that produced the short and long delays to shock equally. Neither oxycodone nor methylphenidate produced dose-related changes in sensitivity to delayed shock at a dose, or doses, that did produce general disruption of behavior. Difficulties of studying drug effects on self-control with aversive events are discussed.

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