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Friday 25 November 2016

Robust representations of individual faces in chimpanzees (Pan troglodytes) but not monkeys (Macaca mulatta).

2016 Nov 19. [Epub ahead of print]


Author information

  • 1Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30329, USA. jesstaubert@gmail.com.
  • 2The National Institute of Mental Health, Bethesda, MD, 20814, USA. jesstaubert@gmail.com.
  • 3Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30329, USA.
  • 4Division of Psychiatry and Behavioral Sciences, Emory University, Atlanta, GA, 30322, USA.

Abstract

Being able to recognize the faces of our friends and family members no matter where we see them represents a substantial challenge for the visual system because the retinal image of a face can be degraded by both changes in the person (age, expression, pose, hairstyle, etc.) and changes in the viewing conditions (direction and degree of illumination). Yet most of us are able to recognize familiar people effortlessly. A popular theory for how face recognition is achieved has argued that the brain stabilizes facial appearance by building average representations that enhance diagnostic features that reliably vary between people while diluting features that vary between instances of the same person. This explains why people find it easier to recognize average images of people, created by averaging multiple images of the same person together, than single instances (i.e. photographs). Although this theory is gathering momentum in the psychological and computer sciences, there is no evidence of whether this mechanism represents a unique specialization for individual recognition in humans. Here we tested two species, chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta), to determine whether average images of different familiar individuals were easier to discriminate than photographs of familiar individuals. Using a two-alternative forced-choice, match-to-sample procedure, we report a behaviour response profile that suggests chimpanzees encode the faces of conspecifics differently than rhesus monkeys and in a manner similar to humans.

KEYWORDS:

Chimpanzees; Face perception; Face recognition; Familiarity; Image averaging; Rhesus monkeys