The organization of conspecific face space in nonhuman primates

• Type of Material: Article
• Authors: Lisa A. Parr, Emory University; Jessica Taubert, Universite Catholique de Louvain; Anthony C. Little, University of Stirling; Peter J. B. Hancock, University of Stirling
• Language: English
• Date: 2012-12
• Publisher: Taylor & Francis (Psychology Press)
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2012 The Experimental Psychology Society
• Final Published Version (URL): http://dx.doi.org/10.1080%2F17470218.2012.693110
• Title of Journal or Parent Work: Quarterly Journal of Experimental Psychology
• ISSN: 1747-0218
• Volume: 65
• Issue: 12
• Start Page: 2411
• End Page: 2434
• Grant/Funding Information: This investigation was supported by the National Center for Research Resources P51RR165 and is currently supported by the Office of Research Infrastructure Programs/OD P51OD11132, and R01-MH068791 to L. A. Parr.
• Keywords: Chimpanzee; Multidimensional scaling; Face identity; Rhesus monkey; Species differences; Face space
• Research Categories: Psychology, Experimental

Abstract

Humans and chimpanzees demonstrate numerous cognitive specializations for processing faces, but comparative studies with monkeys suggest that these may be the result of recent evolutionary adaptations. The present study utilized the novel approach of face space, a powerful theoretical framework used to understand the representation of face identity in humans, to further explore species differences in face processing. According to the theory, faces are represented by vectors in a multidimensional space, the centre of which is defined by an average face. Each dimension codes features important for describing a face’s identity, and vector length codes the feature’s distinctiveness. Chimpanzees and rhesus monkeys discriminated male and female conspecifics’ faces, rated by humans for their distinctiveness, using a computerized task. Multidimensional scaling analyses showed that the organization of face space was similar between humans and chimpanzees. Distinctive faces had the longest vectors and were the easiest for chimpanzees to discriminate. In contrast, distinctiveness did not correlate with the performance of rhesus monkeys. The feature dimensions for each species’ face space were visualized and described using morphing techniques. These results confirm species differences in the perceptual representation of conspecific faces, which are discussed within an evolutionary framework.