Sensitivity to cognitive effort in rhesus macaques Open Access

Abstract

Humans are sensitive to cognitive effort and can use it to guide behavior. If I ask you to remember a phone number with the area code, then the phone number without the area code, you will likely report that it took more effort to remember the phone number with the area code. This feeling is known as cognitive effort. Although cognitive effort sensitivity in humans is well demonstrated, few studies have investigated whether animals are also sensitive to the cost of exerting cognition. We investigated cognitive effort sensitivity in monkeys using a perceptual metacognition paradigm that allowed monkeys to accept or decline tests that varied in the fineness of the discrimination required. In Experiment 1, we found that monkeys declined finer discriminations even when accuracy was at ceiling. These findings were unlikely to be explained by differences in response latency, though monkeys may have generalized the low reward rate of the finest discrimination level to decline less fine discriminations. In Experiment 2, we evaluated whether reward rate generalization could account for subjects’ decline behavior by testing monkeys with stimuli that varied in brightness in addition to the size variation used in Experiment 1. Monkeys were more likely to decline dimmer tests even when accuracy was not affected, consistent with sensitivity to cognitive effort but not generalization along the reinforcement gradient established in Experiment 1. However, the stimulus titration process occasionally exposed monkeys to stimuli that were too dim, possibly causing them to decline dimmed trials due to neophobia. In Experiment we found a contrast effect by presenting runs of very fine or less fine discriminations, followed by a probe trial of a given fineness. Our findings suggest that monkeys may be sensitive to cognitive effort, but other explanations for our findings remain.

Table of Contents

Introduction………………………………………………………………………………………1

Methods………………………………………………………………………………………..….7

Subjects………………………………………………........……………….…………………....7

Apparatus………………………………………………........…………………..……………...7

Data Analysis…………………………….……………........…………………………………..8

Task Training…………………………….……………........…………………………………..8

Experiment 1………………………………………….........…………………………………..10

Experiment 2………………………………………………….........…………………………..16

Experiment 3……………………………………………………….........…………………..…23

General Discussion…………………………………………………………………..……...….29

References………………………………………………………………………………..…….…33

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Psychology, Behavioral Psychology, Cognitive
Keyword	Cognitive Effort Metacognition Cognitive Control Perceptual Discrimination Macaques
Committee Chair / Thesis Advisor	Dr. Robert Hampton, Emory University
Committee Members	Dr. Benjamin Wilson, Emory University Dr. Keith Easterling, Emory University

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