An assessment of cognitive control in monkeys and orangutans Open Access

Brady, Ryan (Summer 2020)

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Cognitive control is a suite of cognitive mechanisms central to human intelligence, including

working memory and metacognition. While the study of cognitive control is central to human

psychology and neuroscience, our understanding of the evolutionary origins of cognitive control

is only beginning to develop. In this dissertation, I present three projects that assess

characteristics of cognitive control in nonhuman primates. In Chapter 2, I report a double

dissociation of cognitively controlled working memory and automatic familiarity in rhesus

monkeys. These results suggest that contributions of working memory are greatest for familiar

images, and when familiarity is not a reliable signal to support recognition memory. In Chapter

3, I report that orangutans rely more heavily on working memory in recognition memory

paradigms compared to rhesus monkeys, supporting the view that the relatively large prefrontal

cortex of great apes results in increased proficiency of working memory and cognitive control. I

found no evidence of familiarity in recognition memory tests in orangutans. In contrast, rhesus

monkeys rely greatly on familiarity in these tests. These results reveal a surprising lack of

familiarity in memory in orangutans that suggests that the relations between memory and frontal

lobe expansion may be complicated. Finally, in Chapter 4 I report that rhesus monkeys

continually monitor their decision making process in a categorization task, and engage cognitive

control to collect sufficient information to ensure accurate performance. These results suggest

that monkeys sometimes monitor evolving cognitive states in real time, resembling the dynamic

relationship between cognitive monitoring and cognitive control found in humans. Taken

together, the projects that form this dissertation advance our understanding of the characteristics

of cognitive control in nonhuman primates, and provide insights toward understanding the

evolutionary origins of cognitive control.

Table of Contents

Chapter 1: General Introduction                                                                                       8

Chapter 2: Paper 1: Nonverbal working memory for novel images in rhesus monkeys

Title & Abstract                                                                                                         16

Introduction                                                                                                               17

Experiment 1a                                                                                                            20

Experiment 1b                                                                                                           22       

Experiment 2                                                                                                             24

Experiment 3                                                                                                             27

Experiment 4                                                                                                             29

Discussion                                                                                                                  32

Methods                                                                                                                     36

Chapter 3: Paper 2: Greater recruitment of working memory and extremely restricted familiarity in orangutans compared to rhesus monkeys

Title & Abstract                                                                                                         40

Introduction                                                                                                               41

Experiment 1                                                                                                             44

Experiment 2                                                                                                             49

Experiment 3                                                                                                             56

Experiment 4                                                                                                             61

Discussion                                                                                                                 65

Chapter 4: Paper 3: Rhesus monkeys (Macaca mulatta) monitor evolving decisions to control adaptive information seeking

Title & Abstract                                                                                                         71

Introduction                                                                                                               72

Experiment 1                                                                                                             76

Experiment 2                                                                                                             80

Experiment 3                                                                                                            84

Discussion                                                                                                                  88

Chapter 5: General Conclusion                                                                                          93

References                                                                                                                           102

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