NONHUMAN PRIMATES IN SOCIAL RESEARCH 
Nonhuman primates are uniquely valuable as models of complex human phenomena because 
they are closer to humans in evolutionary history, brain structure/function, and social 
structure and organization. Early studies in monkeys and apes demonstrated dramatically the 
profound effects of altered early social experience on later individual and social behavior, and 
on adult behavioral and reproductive competence (Harlow et ah, 1965). Later work, using 
maternal separation in young monkeys, demonstrated not only immediate behavioral 
responses to separation, but significant endocrinological and immunological consequences as 
well (Suomi, 1997). Studies emphasizing alterations in behavioral and physiological 
development can now be expanded to include studies of altered development of basic brain 
mechanisms and potential remediation. Social rearing parameters described below refer 
primarily to nonhuman primate data, and within the nonhuman primates, primarily to Old 
World monkeys, which have been the most extensively studied, and for which most data are 
available. Atypical early experience in primates usually results in the appearance of species 
atypical behaviors. Such behaviors may reflect adaptive changes, rather than pathological, in 
psychological development. Primates raised with absent or deviant social experience will 
develop very differently from those raised with species-appropriate experience (Bayne and 
Novak, 1998), but such altered developmental trajectories, while differing behaviorally from 
species-typical behaviors, need not be equated with stress. 
CONSPECIFIC 
Social primates have the highest probability of developing in a species-typical manner if 
reared in a social environment modeled after those found in the wild. This may be especially 
important when a research program requires subjects typical of those found in the wild, 
because lab-reared individuals may vary in behavioral characteristics. 
PEER REARING 
Monkeys raised only with peers may develop sufficient social skills to permit their 
introduction to more species-typical social groups later in life, but their social repertoires 
remain somewhat atypical. Typically, peer-rearing paradigms include removing infants from 
their mothers within 24 to 48 hours of birth, placing them in a temperature- and light- 
controlled environment, hand feeding them until they are able to nurse from a bottle 
unsupported, and placing them with a similar-age peer within the first week or two of life. 
Peer-reared animals will develop strong attachments to each other, and protest vigorously 
when separated from each other, but the physiological response to separation from a peer is 
not as profound as is separation from the mother (Boccia et al., 1989). 
SURROGATE AND ISO^TION REARING 
Surrogate-reared animals are also separated from their mothers shortly after birth, and like 
peer-reared animals, they are fed by hand until they are able to feed themselves. Instead of 
86 
