This project investigates how rhesus monkeys and other nonhuman primate species born and raised under different laboratory conditions adapt to placement into environments that contain specific physical and social features of the monkeys' natural habitat. Adaptation is assessed by examining behavioral repertoires and by monitoring a variety of physiological systems in these subjects, yielding broad-based indices of relative physical and psychological well-being. The responses of subjects to experimental manipulations of selected features of their respective environments are also assessed in similar fashion. Whenever, possible field data are collected for appropriate comparisons. An additional focus is on investigating the cognitive, behavioral, and social processes involved in adaptation to new settings or circumstances. Capuchin monkeys are employed in many of these studies because they are unique among monkey species in their propensity to manufacture and use tools to modify their physical environment. Research carried out during FY96 (a) documented species-normative age, gender, dominance, and seasonal influences on behavioral repertoires and adrenocortical responsiveness among the rhesus monkeys maintained in the LCE's 5-acre outdoor enclosure following completion of a new shelter facility; (b) identified developmentally stable individual differences in behavioral, psychophysiological, and adrenocortical reactions to environmental challenges in wild-living rhesus monkey infants and juveniles; (c) demonstrated significant relationships between heartrate and adrenocortical responsiveness and specific aspects of maternal behavior in wild-living rhesus monkey females; (d) developed computer-based procedures for testing memory capabilities of captive rhesus monkeys; (e) characterized developmental, postural, and task-specific correlates of handedness in capuchin monkeys; and (f) expanded the known range of complex tool-using behaviors in captive capuchin monkeys and documented the sharing of both food and tools between small social groups housed in adjacent pens.