Morphological variants of silent bared-teeth displays have different social interaction outcomes in crested macaques (Macaca nigra)

Clark, P.R., Waller, B.M. ORCID: 0000-0001-6303-7458, Burrows, A.M., Julle‐Danière, E., Agil, M., Engelhardt, A. and Micheletta, J., 2020. Morphological variants of silent bared-teeth displays have different social interaction outcomes in crested macaques (Macaca nigra). American Journal of Physical Anthropology, 173 (3), pp. 411-422. ISSN 1096-8644

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Abstract

Objectives: While it has been demonstrated that even subtle variation in human facial expressions can lead to significant changes in the meaning and function of expressions, relatively few studies have examined primate facial expressions using similarly objective and rigorous analysis. Construction of primate facial expression repertoires may, therefore, be oversimplified, with expressions often arbitrarily pooled and/or split into subjective pigeonholes. Our objective is to assess whether subtle variation in primate facial expressions is linked to variation in function, and hence to inform future attempts to quantify complexity of facial communication.

Materials and Methods: We used Macaque Facial Action Coding System, an anatomically based and hence more objective tool, to quantify “silent bared‐teeth” (SBT) expressions produced by wild crested macaques engaging in spontaneous behavior, and utilized discriminant analysis and bootstrapping analysis to look for morphological differences between SBT produced in four different contexts, defined by the outcome of interactions: Affiliation, Copulation, Play, and Submission.

Results: We found that SBT produced in these contexts could be distinguished at significantly above‐chance rates, indicating that the expressions produced in these four contexts differ morphologically. We identified the specific facial movements that were typically used in each context, and found that the variability and intensity of facial movements also varied between contexts.

Discussion: These results indicate that nonhuman primate facial expressions share the human characteristic of exhibiting meaningful subtle differences. Complexity of facial communication may not be accurately represented simply by building repertoires of distinct expressions, so further work should attempt to take this subtle variability into account.

Item Type: Journal article
Publication Title: American Journal of Physical Anthropology
Creators: Clark, P.R., Waller, B.M., Burrows, A.M., Julle‐Danière, E., Agil, M., Engelhardt, A. and Micheletta, J.
Publisher: Wiley on behalf of the American Association of Physical Anthropologists
Date: November 2020
Volume: 173
Number: 3
ISSN: 1096-8644
Identifiers:
NumberType
10.1002/ajpa.24129DOI
1372153Other
Rights: © 2020 The Authors. American Journal of Physical Anthropology published by Wiley Periodicals LLC. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Divisions: Schools > School of Social Sciences
Record created by: Jill Tomkinson
Date Added: 13 Oct 2020 14:08
Last Modified: 24 Nov 2020 11:44
URI: http://irep.ntu.ac.uk/id/eprint/41283

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