Mapping the contribution of single muscles to facial movements in the rhesus macaque

DOI

10.1016/j.physbeh.2008.05.002

Document Type

Journal Article

Publication Date

9-3-2008

Publication Title

Physiology and Behavior

Volume

95

Issue

2022-01-02

First Page

93

Last Page

100

ISSN

319384

Keywords

Emotion, Facial expression, FACS, Intramuscular electrical stimulation, Monkey, Primate

Abstract

The rhesus macaque (Macaca mulatta) is the most utilized primate model in the biomedical and psychological sciences. Expressive behavior is of interest to scientists studying these animals, both as a direct variable (modeling neuropsychiatric disease, where expressivity is a primary deficit), as an indirect measure of health and welfare, and also in order to understand the evolution of communication. Here, intramuscular electrical stimulation of facial muscles was conducted in the rhesus macaque in order to document the relative contribution of each muscle to the range of facial movements and to compare the expressive function of homologous muscles in humans, chimpanzees and macaques. Despite published accounts that monkeys possess less differentiated and less complex facial musculature, the majority of muscles previously identified in humans and chimpanzees were stimulated successfully in the rhesus macaque and caused similar appearance changes. These observations suggest that the facial muscular apparatus of the monkey has extensive homology to the human face. The muscles of the human face, therefore, do not represent a significant evolutionary departure from those of a monkey species. Thus, facial expressions can be compared between humans and rhesus macaques at the level of the facial musculature, facilitating the systematic investigation of comparative facial communication. © 2008 Elsevier Inc. All rights reserved.

Open Access

Green Accepted

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