Early stress and adult emotional reactivity in rhesus monkeys.

This chapter examines the relationship between early social experiences and behavioural and emotional reactivity in adolescence and adulthood that has been established through extensive research with rhesus monkeys. Classic studies carried out in the 1960s first demonstrated that rearing under conditions of social isolation resulted in severe behavioural abnormalities that carried over into adulthood. In the 1970s techniques for reversing such isolation-induced deficits were developed. More recent studies have examined the long-term consequences of more subtle variation in early rearing environments. Monkeys reared from birth without mothers but with extensive peer contact develop relatively normal social behavioural repertoires and function well in familiar and stable social settings. However, peer-reared monkeys display extreme behavioural and physiological reactions to environmental challenges, such as brief social separation, later in life. In contrast, monkeys reared by unusually nurturant foster mothers appear to develop effective strategies for coping with subsequent environmental challenges. Some general principles that have emerged from these studies with rhesus monkeys will be outlined and their implications regarding possible relationships between early social experiences and responses to challenge later in life in humans will be discussed.