A Test of Inhibitory Resource Depletion in Rhesus Macaques (Maccaca mulatta) Open Access

Greenlaw, Celia (2016)

Permanent URL: https://etd.library.emory.edu/concern/etds/hq37vn66k?locale=en


Inhibitory control is a critical component of human cognition and behavior. According to the Strength Model, all inhibitory control behaviors rely on the same limited resource, and exerting inhibitory control depletes this resource. Support for this model comes from experiments showing that when humans experience consecutive tasks requiring inhibitory control, performance is impaired on the second task. In humans, this phenomenon is called ego depletion, but for nonhuman animals we will refer to it as inhibitory resource depletion. The Strength Model has been studied and debated extensively in humans, but little work has been done in nonhuman primates. The current study was designed to test whether rhesus macaques (Macaca mulatta) experience inhibitory resource depletion. Five monkeys were tested using touchscreen computer adaptations of the Flanker Task and the Wisconsin Card Sorting Test (WCST). The monkeys first completed 150 Flanker trials that were entirely incongruent, congruent, or absent. Incongruent flankers were designed to tax inhibitory control, whereas congruent and absent flankers do not. After the Flanker Task, the monkeys performed the WCST until they completed a WCST rule-switch. The WCST involves two rules, color or shape, and the monkeys respond based on the currently reinforced rule. Following a rule-switch, inhibitory control gets taxed because the subject must inhibit their learned response to the previously reinforced rule. We hypothesized that if inhibitory control behaviors in rhesus macaques rely on a limited resource, then monkeys will exhibit significantly impaired performance on the WCST rule-switch following incongruent flanker trials, compared to congruent or absent flanker trials. There was no apparent effect of inhibitory resource depletion in this experiment, as performance did not vary significantly following different Flanker types. Experimental design manipulations that may better assess inhibitory resource depletion are discussed.

Table of Contents

Introduction Pages 1-7

Methods Pages 7-10

Results Pages 10-11

Discussion Pages 11-15

Figures Pages 16-23

References Pages 24-28

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