Development of face recognition in infant chimpanzees (Pan troglodytes)

In this paper, we assessed the developmental changes in face recognition by three infant chimpanzees aged 1-18 weeks, using preferential-looking procedures that measured the infants' eye- and head-tracking of moving stimuli. In Experiment 1, we prepared photographs of the mother of each infant and an “average” chimpanzee face using computer-graphics technology. Prior to 4 weeks of age, the infants showed few tracking responses and no differential responses. Between 4 and 8 weeks of age, they paid greater attention to their mother's face. From 8 weeks onward, they again showed no differences, but exhibited frequent tracking responses. Experiment 2 investigated the infants' tracking responses between a familiar human's and an “average” human face. The infants did not show any evidence of recognizing the human faces. We discuss the development of face recognition in relation to the effects of other species' faces and postnatal visual experience.