Testing the Glucose Hypothesis among Capuchin Monkeys: Does Glucose Boost Self-Control?

Audrey Parrish,Mattea Rossettie,Michael Beran,Ishara Emerson

doi:10.3390/bs6030016

Audrey Parrish, Mattea Rossettie + Show 2 more

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https://doi.org/10.3390/bs6030016

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Abstract

The ego-depletion hypothesis states that self-control diminishes over time and with exertion. Accordingly, the glucose hypothesis attributes this depletion of self-control resources to decreases in blood glucose levels. Research has led to mixed findings among humans and nonhuman animals, with limited evidence for such a link between glucose and self-control among closely-related nonhuman primate species, but some evidence from more distantly related species (e.g., honeybees and dogs). We tested this hypothesis in capuchin monkeys by manipulating the sugar content of a calorie-matched breakfast meal following a nocturnal fast, and then presenting each monkey with the accumulation self-control task. Monkeys were presented with food items one-by-one until the subject retrieved and ate the accumulating items, which required continual inhibition of food retrieval in the face of an increasingly desirable reward. Results indicated no relationship between self-control performance on the accumulation task and glucose ingestion levels following a fast. These results do not provide support for the glucose hypothesis of self-control among capuchin monkeys within the presented paradigm. Further research assessing self-control and its physiological correlates among closely- and distantly-related species is warranted to shed light on the mechanisms underlying self-control behavior.

Highlights

Marathon runners condition their bodies across weeks of training, toning their muscles and strengthening their mind-set, all the while exhibiting impressive feats of physical and mental self-control and dedication in the effort to cross the finish line
The strength model of self-control, known as the limited resource or ego-depletion hypothesis, states that self-control diminishes with each exertion or expression of such control, such that there are subsequently fewer resources available for future circumstances requiring self-control (e.g., [2,3])
The present results argue against a link between glucose and self-control from a comparative perspective, at least when methods to deplete such self-control are not employed

Summary

Introduction

Marathon runners condition their bodies across weeks of training, toning their muscles and strengthening their mind-set, all the while exhibiting impressive feats of physical and mental self-control and dedication in the effort to cross the finish line. Research documented compromised self-control performance among individuals participating in a series of un-related self-control tasks, such that fewer resources were available for tasks occurring later in the sequence. In the earliest ego-depletion study using the dual-task paradigm, participants were either instructed to regulate their emotions (or not) while watching an emotional film. Those participants who exercised self-control to regulate their emotions during the film performed poorer on a subsequent self-control measure of physical strength (stamina during a handgrip task) than participants who did not suppress their emotions [4].

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