Discrimination of Facial Expressions in Tufted Capuchin Monkeys (Sapajus apella) Público

Abstract

Abstract
Discrimination of Facial Expressions in Tufted Capuchin Monkeys ( Sapajus apella)
Facial expressions are important signals that facilitate primate social interactions.
Tufted capuchins ( Sapajus apella) readily discriminate conspecific faces and categorize
them according to group membership. In three experiments, we examined whether this
discrimination extends to facial expressions and how the discrimination is made. We
tested whether tufted capuchins discriminate between neutral expressions and either
affiliative eyebrow flash expressions or agonistic open-mouth threat expressions, whether
the presence of salient facial features was sufficient for tufted capuchins to make such
discriminations, and whether they demonstrated an inversion effect. Data were collected
from nine adult and sub-adult monkeys using an oddity paradigm on touchscreen
computers. Subjects discriminated between emotional and neutral expressions
significantly above chance. Furthermore, they discriminated between open-mouth threats
and neutral expressions with varying degrees of visible teeth and mouth opening
significantly better than chance in all conditions and showed evidence of an inversion
effect. These results suggest that discriminating emotional facial expressions is an
important aspect of tufted capuchin communication and that like humans and
chimpanzees, holistic, rather than feature-based processing is the dominant mechanism.
By investigating the similarities in face processing between species, we gain a deeper
understanding of the evolution of facial expressions as parts of communication systems.

Discrimination of Facial Expressions in Tufted Capuchin Monkeys ( Sapajus apella)
B.A., College of William & Mary, 2008
Advisor: Frans B.M. de Waal, Ph.D.
A thesis submitted to the Faculty of the James T. Laney School of Graduate Studies of
Emory University in partial fulfillment of the requirements for the degree of Master of
Arts in Psychology 2012.

Table of Contents

Table of Contents

Introduction








1
Hypotheses & Predictions







8

Experiment 1







8

Experiment 2







9

Experiment 3







10
Method









10

Subjects








10

Apparatus








12

Design & Procedure






13

Stimuli








14


Experiment 1






15


Experiment 2






16


Experiment 3






16
Results









17

Experiment 1







17

Experiment 2







19

Experiment 3







23

Age, Rank, and Sex Analyses





25
Discussion









26
Conclusion









29
References









30
Appendix A








34

About this Master's Thesis

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• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Laney Graduate School
Department	Psychology
Degree	MA
Submission	Master's Thesis
Language	English
Research Field	Psychology, Behavioral Psychology, Experimental Psychology, Cognitive
Palabra Clave	facial expressions social cognition
Committee Chair / Thesis Advisor	De Waal, Frans B M, Emory University
Committee Members	Rodman, Hillary R, Emory University Nygaard, Lynne, Emory University

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