The monkey in the mirror: Hardly a stranger

• Type of Material: Article
• Authors: Frans B M De Waal, Emory University; Marietta Dindo, Emory University; Cassiopeia A. Freeman, Emory University; Marisa Hall, Emory University
• Language: English
• Date: 2005-08-09
• Publisher: National Academy of Sciences
• Publication Version: Final Published Version
• Copyright Statement: © 2005 by The National Academy of Sciences of the USA.
• Final Published Version (URL): http://dx.doi.org/10.1073/pnas.0503935102
• Title of Journal or Parent Work: Proceedings of the National Academy of Sciences
• ISSN: 0027-8424
• Volume: 102
• Issue: 32
• Start Page: 11140
• End Page: 11147
• Grant/Funding Information: Research was supported by the National Science Foundation (Grant IBN-0314878); and the National Institutes of Health basegrant (RR-00165) to the Yerkes National Primate Research Center.
• Keywords: Analysis of Variance; Cebus; Empathy; Observation; Recognition (Psychology); Animals; Female; Discrimination (Psychology); Male; Self Concept; Sex Factors
• Research Categories: Psychology, Cognitive; Biology, Zoology

Abstract

It is widely assumed that monkeys see a stranger in the mirror, whereas apes and humans recognize themselves. In this study, we question the former assumption by using a detailed comparison of how monkeys respond to mirrors versus live individuals. Eight adult female and six adult male brown capuchin monkeys (Cebus apella) were exposed twice to three conditions: (i) a familiar same-sex partner, (ii) an unfamiliar same-sex partner, and (iii) a mirror. Females showed more eye contact and friendly behavior and fewer signs of anxiety in front of a mirror than they did when exposed to an unfamiliar partner. Males showed greater ambiguity, but they too reacted differently to mirrors and strangers. Discrimination between conditions was immediate, and blind coders were able to tell the difference between monkeys under the three conditions. Capuchins thus seem to recognize their reflection in the mirror as special, and they may not confuse it with an actual conspecific. Possibly, they reach a level of self-other distinction intermediate between seeing their mirror image as other and recognizing it as self.