GRADUAL ACQUISITION OF VISUAL-DISCRIMINATION TASKS IN A SOCIAL GROUP OF RHESUS-MONKEYS (MACACA-MULATTA)

An established, captive colony of 74 rhesus monkeys (Macaca mulatta) w as group-tested on a simultaneous visual discrimination problem and th ree reversals of the initial discrimination. The task incorporated imp ortant aspects of rhesus foraging behavior. Although other studies of communal groups of nonhuman primates have reported rapid learning, sub jects in the present study showed no evidence of one-trial acquisition of the initial problem or of rapid learning-set formation across the reversal series. Instead, mean and individual performance, on all vari ables measured, improved gradually, both within and across series. Sub jects appeared to ''learn how to learn,'' consistent with findings of traditional studies of individual discrimination learning. Our finding of gradual learning in group-living animals argues that the source of rapid learning in previous reports is not attributable to social infl uence or ecological relevance, but may reflect specific procedural or species differences between studies.