Sensitivity to Spatial Sequence with Geometric Regularity in Humans and Rhesus Macaques Open Access

Abstract

Sequence learning supports the prediction and organization of patterned behavior in motor, spatial, and cognitive tasks. Although many species can learn sequential patterns, prior works suggest that humans may possess specialized sensitivity to higher-order relational structure and form compressed representations for sequences embedded in geometric regularities. Whereas surprisingly, non-human primates don’t seem to have this ability and rely heavily on item-by-item conjunctive coding. This ability to compress regularities is particularly notable because it allows humans to reduce complex sequential input into simple abstract rules, and has been proposed as a key cognitive difference between humans and other animals. Understanding whether non-human primates share this capacity is important to clarify whether this ability is a distinguishing feature of human cognition. To address this question, we conducted a visuospatial serial reaction time task and a sequence completion task to compare the ability of humans and rhesus macaques to learn regular and irregular spatial sequences. We found that humans showed clear sensitivity to geometric regularity in sequences, as they responded faster and achieved higher accuracy to regular than irregular sequences, particularly later in the sequence when more structural information was available. In contrast, monkeys showed no reliable evidence of regularity learning in the serial reaction time task. In the original sequence completion task copied from the human study, the monkey’s performance remained below chance, suggesting no successful prediction of upcoming sequence elements. However, in a follow-up sequence completion task that reduced the monkey’s cognitive demands by simplifying the response options, the monkey’s performance improved, with above-chance accuracy in the regular condition. Together, these findings demonstrated that humans readily process geometric sequence structure and rhesus macaques do not, while also indicating that monkeys may still express a limited sensitivity to relational structure under simplified conditions with lower cognitive demands. 

Table of Contents

Introduction………………………………………………………………………………………..1 

Methods……………………………………………………………………………………………6 

Results……………………………………………………………………………………………11 

Discussion………………………………………………………………………………………. 14 

Figures……………………………………………………………………………………………19 

Figure 1…………………………………………………………………………………..19 

Figure 2…………………………………………………………………………………..20 

Figure 3…………………………………………………………………………………..21 

Figure 4…………………………………………………………………………………..24 

Tables…………………………………………………………………………………………….26 

Table 1……………………………………………………………………………………26 

Table 2……………………………………………………………………………………27 

References……………………………………………………………………………..................28

About this Honors Thesis

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School	Emory College
Department	Psychology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Psychology, Cognitive
Keyword	geometric regularity comparative cognition rhesus macaques sequence learning
Committee Chair / Thesis Advisor	Wilson Benjamin, Emory University
Committee Members	Lonsdorf Elizabeth, Emory University Hampton Robert, Emory University

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