- 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
