Nocturnal sleep in isolation-reared monkeys: evidence for enviromental independence

Thirteen all-night recordings were obtained from 3 infant pigtailed (Macaca nemestrina) monkeys raised on a cloth surrogate mother and under conditions of social isolation. Totally implantable biotelemetry systems were used to record the sleep physiology from the unrestrained animals. Sleep stages and night-to-night variability were virtually identical to values previously found in 8 mother-reared group-living infants. Sustained alterations in the early rearing enviroment, even though considerably modifying the organism's development, did not appear to result in differences in sleep organization.