Each of eight infant rhesus monkeys was paired with a preadolescent conspecific for two months and then separated. Four of the infants were mother-reared and four were isolate-reared. Separation responses were compared with data from preseparation and reunion phases of the study for all pairs. The results indicate that (1) although males interact with infants in a parental fashion, preadolescent females show a greater capacity for parental behavior, (2) both preadolescents and normal (mother-reared) infants contribute to the development of a social bond, (3) isolate infants contributed little to the development of a social bond and were relatively less-valued as social partners by their preadolescent cagemates.