The evolutionary origins of executive functions : behavioural control in humans and chimpanzees
Abstract
Executive functions (EFs) are a set of cognitive operations, including working memory, inhibitory
control and attention shifting, that underpin accurate, flexible and coordinated behaviour in
many problem-solving contexts. While it seems likely that humans surpass nonhuman animals
in EFs, previous research into the evolutionary origins of EFs is limited and lacks systematic
comparisons of EFs in human and nonhuman animals.
In this thesis, I aimed to overcome these limitations by developing a test battery to study EFs in
our closest primate relative, the chimpanzee. Using an individual differences approach, I
investigated the performance of 19 chimpanzees on several EF tasks and extracted two factors
in an exploratory factor analysis accounting for 70.9 % of the variability. The two measures of
working memory loaded onto one factor, suggesting that a common cognitive process underlay
performance on both tasks. This factor could be clearly differentiated from a well-established
measure of attention shifting, loading onto a second factor. In addition, the measures of
inhibitory control did not contribute to a unique factor. Intriguingly, the emerging structure of
separable EF processes, paralleled the EF structure suggested for human adults (Miyake et al,
2012).
The subsequent comparison of a sub-sample of chimpanzees (n = 12; excluding aged
individuals), pre-schoolers (n = 36) and undergraduates (n = 16) on two selected EF tests
revealed impressive EF capacities of chimpanzees. Chimpanzees could deal with interference
in working memory at levels comparable to four and five year-olds. Additionally, the ability of
chimpanzees to shift attention was not significantly different from four year-olds; however, five-
year-olds outperformed their primate relatives. My work suggests that important aspects of EFs are shared between humans and chimpanzees; while performance differences in EFs emerge
late in human ontogeny. The implications of my results for theories on human cognitive
evolution are discussed.
Type
Thesis, PhD Doctor of Philosophy
Rights
Embargo Date: 2021-03-10
Embargo Reason: Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 10th March 2021
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