The Evolutionary Origins of Executive Function in Primates: An Individual Differences Approach
Creators: name: Cantwell, Averill
Publisher: name: My University
Year: 2024
Subjects: subject: Executive function
subject: Primate cognition
subject: Science (General)
subject: Science

description: Executive function is a suite of cognitive abilities that enables flexible, goal-oriented behavior. These abilities – including inhibitory control, working memory, and cognitive flexibility – are central to ‘intelligent’ behavior, allowing an individual to plan, monitor, and adjust behavior to achieve a goal. Neurobiologists have highlighted significant changes to the human prefrontal cortex, the ‘seat’ of executive function, that suggest these abilities were enhanced in human evolution, leading to more complex, flexible behavior. However, direct comparative evidence characterizing executive function in other primates is limited. In this dissertation, I investigate the structure, development, and role of executive function in non-human primates using an individual differences approach. While animal cognition has often focused on species’ averages, investigating the causes and consequences of individual variation within species is key to understanding how cognition evolves. This approach opens up a different set of questions, including how individual performance is linked across cognitive measures, how age and sex influence performance, and how cognition contributes to behavior. In Chapter 2, I first test whether cognitive flexibility, one core component of executive function, is linked to temperament. Specifically, I test a proposed link between ‘shy’ temperament and increased cognitive flexibility within seven lemur species that vary in social and ecological features. I find an overall relationship in the predicted direction, but some evidence that this link may be influenced by species’ feeding ecology. In Chapters 3 and 4, I assess the development of chimpanzee executive function as well as patterns of individual differences in these skills. In Chapter 3, I find slow developmental improvement in a measure of cognitive flexibility, a pattern shared with humans. In Chapter 4, I develop a novel test battery to examine individual variation in executive function as well as other complex social and non-social skills. I detect both developmental improvement in most executive function measures as well as early declines in older age, another feature shared with humans. I also find targeted sex differences in both studies indicating a female advantage in cognitive flexibility. In Chapter 4, I also use this test battery to assess patterns of performance across cognitive skills in chimpanzees. Specifically, I investigate whether executive function forms a distinct cluster of abilities in chimpanzees when contrasted with other individual reasoning, social reasoning, and temperament skills. I find relationships among most executive function skills, suggesting that executive function represents a coherent suite of abilities in chimpanzees. Finally, in Chapter 5 I investigate whether individual differences in cognition can be linked to real-world behavior in chimpanzees. First, I calculate social rank from two years of observational behavioral data for a subset of chimpanzees tested in the cognitive battery from Chapter 4. I then test the effects of rank on performance in executive function measures. I find that both low- and high-ranking males exhibit better performance in specific skills. I then test whether executive function is linked to observational metrics of social and ecological behavior in chimpanzees. I find evidence that specific executive function skills can have both positive and negative effects on flexible behaviors across domains. Overall, this dissertation examines the nature and role of executive function within primate species, highlighting the value of an individual differences approach to investigate the structure and function of complex cognition.