Date of Award:

8-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Psychology

Committee Chair(s)

Timothy A. Shahan

Committee

Timothy A. Shahan

Committee

Kerry E. Jordan

Committee

Gregory J. Madden

Abstract

Foraging animals in natural environments must track the value of different behavioral options in order to make decisions that maximize their food intake. The process by which they track this value is poorly understood, but holds relevance for our understanding of how animals make choices in general. In a series of experiments conducted in operant chambers, we put rat subjects in a choice scenario where they could press two levers, one of which would intermittently produce the delivery of food pellets on a rich (more frequent) schedule, while the other would do the same on a lean (less frequent) schedule. We switched which lever was richly baited and which lever was leanly baited during a second phase of reinforcement, then imposed test delays where subjects were maintained at weight in their home cages before conducting test sessions in which neither lever was baited. Using this approach, we examined how the relative value of options (as measured by preference between those options) changes over time. Our procedure was explicitly designed to produce a phenomenon called spontaneous recovery of choice, in which a test delay results in a change in preference between options. This phenomenon has been previously linked to relapse in addiction or problem behavior treatment, and is not accounted for by dominant models of how animals track value. Test session data from the three experiments show compelling evidence of this phenomenon, but are inconsistent with previous work on the topic. Several models are applied to the data and compared quantitatively, and various interpretations are discussed.

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