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Student Prize Award Abstract
1996 Oral Paper Honorable Mention


L.A. Parr1,3, W.D. Hopkins2,3, and F.B.M. de Waal3
1Department of Psycology, Emory University, Atlanta, GA 30322, 2Berry College, Rome, GA 30149, and 3Yerkes Regional Primate Research Center, 954 N. Gatewood Rd., Atlanta, GA 30329, U.S.A.

Five chimpanzees were tested on their ability to discriminate faces in three separate tasks. Discriminanda were digitized black & white photographs of unfamiliar chimpanzee faces with neutral expressions, presented in a zero-delay matching-to-sample format. Subjects moved a joystick controlled cursor on a computer monitor to select one of two laterally presented stimuli that matched a sample above. First, during initial training four subjects reached a criterion of >75% correct on 25 identity matching stimulus sets after <80 trials. Second, an individual recognition test combined 14 unique stimulus sets, where the correct pairs were two different photographs of the same individual, with 10 novel identity matching sets. Subjects performed significantly above chance on their first exposure to these 24 novel trials indicating their ability to recognize individuals by face and generalize matching to novel stimuli. Finally, subjects performed an inversion test involving 10 each of upright and inverted shapes and faces. Four of five subjects showed a significant impairment in their discrimination of inverted faces but not of shapes. This provides the first clear evidence of an inversion effect in chimpanzees, indicating that face discrimination in this species may involve a mechanism distinct from that involved with pattern discrimination.

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