The objective of this research was to determine whether access to mother-peer (MP) reared rhesus monkeys (Macaca mulatta) affected the behavior and physiology of juvenile and adolescent surrogate-peer (SP) and peer-only reared (PR) monkeys. Monkeys were housed in a mixed-rearing group (MP, SP, and PR together) or two same-rearing groups (one MP group and one SP and PR group). The studies of this dissertation used behavior and physiology to test three prediction models: SP and PR monkeys would be more similar to MP monkeys in the mixed-rearing group compared to the same-rearing group (acculturation model), more different (dissimilation model), or there would be no effect of MP monkeys in the mixed-rearing group (stability model). In experiment one, basic behavioral responses of 14-month old nursery reared monkeys were consistent with the stability model; however, SP monkeys showed a greater magnitude of difference in initiated social behavior than PR monkeys. In experiment two, SP monkeys preferred both SP and MP partners almost equally for all behaviors in the mixed-rearing group (acculturation model), whereas PR monkeys showed little fluctuation in partner preferences, preferring primarily other PR monkeys as partners (stability model). Also, there were more aggressive responses to aggressive interactions in SP monkeys in the mixed-rearing group (dissimilation model), whereas PR monkeys were similar to MP monkeys (stability model). In experiment three, plasma cortisol (CORT) of 14- and 26-month old SP monkeys and of 37- and 49-month old SP monkeys was similar to MP monkeys of the same ages. However, CORT of PR monkeys became more similar to MP monkeys over time in the mixed-rearing group. Variation in CORT among differently reared monkeys was also reduced over time. Mixed-rearing housing resulted in behavioral acculturation of SP monkeys and the physiological acculturation of PR monkeys; however, it is possible that SP monkeys showed physiological acculturation prior to our blood sampling and PR monkeys showed behavioral acculturation after our behavioral sampling. Thus, future studies evaluating monkeys in same- and mixed-rearing groups are necessary in order to examine this timing effect of behavioral and physiological acculturation.