Early social experience and responses to visual social stimuli in young monkeys

Juvenile stumptailed macaques (Macaca arctoides) were given preference tests in which they could approach an empty chamber, a mirror, a familiar conspecific, or an unfamiliar conspecific. Control subjects tended to withdraw from the mirror, and threatened the stranger more than did monkeys whose early social experience had occurred exclusively in darkness. Both groups explored the familiar stimulus animal most of all, but the group socialized in the dark showed most positive behavior when in the empty chamber. In a second study peer-reared infants responded more appropriately to slides of conspecifics than did infants reared with a mirror as the main source of social input. Infants reared only with a peer were also strongly attracted to a mirror, whereas infants reared only with mirrors preferred a film of an unfamiliar agemate. The results suggest that early visual social stimulation is important in the development of aggression and other social behaviors, and that novelty and complexity are important aspects of social stimuli that interact with effects of early experience. Study 2 was conducted while the first author was in receipt of a Postgraduate Research Studentship from the U.K. Science Research Council. The DTU tapes were analyzed using a computer program developed with the help of SRC grant B/RG 98910 to A. Chamove. This latter grant also supported the study from which the preference test data were taken.