Previous studies have reported that the maternal behavior of rhesus monkey females who themselves were reared without mothers ("motherless mothers") is generally inadequate and often abusive. The present study examined the maternal competency of SO such subjects with respect to the variables of rearing environment, age at first social contact, sex of offspring, age at first delivery, parity, and duration of exposure to previous offspring. The results suggested that physical contact with conspecifics, either with peers prior to adulthood or with their own infants immediately after birth, greatly reduced the probability that motherless mothers would be inadequate maternally.Researchers who have studied the consequences of social deprivation in rhesus monkeys are in virtual agreement that social isolation or restriction imposed early in life has devastating, and often permanent, effects on the social development of monkeys. As adults, monkeys reared for at least the first 6 months in physical isolation from conspecifics have been reported to exhibit anomalies in home-cage behavior (Cross & Harlow, 196S;Suomi, Harlow, & Kimball, 1971), in adaptation to novel environments (Harlow, Schiltz, & Harlow, 1969), in approach to complex stimuli (Sackett, 1972), and in suppression of ongoing response chains (Sackett, 1970). With respect to social activities, adult isolate-reared monkeys typically display excessive and inappropriately directed aggres-

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Nursery-reared primates do not experience psychological "maternal bonding" or immunological benefits of breast milk, so they are expected to be inferior to mother-raised monkeys in growth, health, survival, reproduction, and maternal abilities. Studies of nursery-reared monkeys support aspects of this prediction for infants deprived of social contact or raised in pairs. We present colony record data on 1,187 mother and 506 nursery-raised monkeys, 2-10 yr of age, living in mixed groups. We found no group differences in survival, growth, clinical treatments for disease or bite wounds, or pregnancy outcome and neonatal deaths. Nursery males given breeding opportunities produced an average of 24 offspring. In addition to 24-hr personnel present on every day of the year, we believe that three of our procedures account for differences between our results and other reports. Our infants received 1) intensive human handling, 2) daily social interaction in a playroom, and 3) success and failure experience during learning and cognitive testing. We do not advocate rearing primates without mothers, but we conclude that these procedures are sufficient for producing physical health and adaptive juvenile and adult social skills in nursery-raised monkeys.

8 isolate monkeys were compared in a follow-up study to 8 sophisticated controls in brief cross-sectional pairings with 12 stimulus strangers: 4 adults, 4 age-mates, and 4 juveniles. The isolates were characterized by infantile disturbance, less environmental orality, more fear, more aggression, less sex, less play, and bizarre ritualistic movements. 12-mo. isolates were fearful and nonaggressive but threatened many attacks. 6-mo. isolates were fearful and physically aggressive. The 12-mo. isolates demonstrated practically no positive social behavior. Conclusions are: (a) 6 mo. of social isolation during the first year has negative effects on social behavior up to puberty, (b) abnormal aggression appears in 3-yr.-old 6-mo. isolates, and (c) 12 mo. of isolation suppress or delay this aggression.

Many scientists and colony managers assume that social housing is a beneficial living condition for all captive primates. Several older studies of primate development question the generality of this assumption. We recently tested this assumption by comparing the social development of pigtailed macaque infants raised in pairs and those that were raised in individual cages. All animals received 30 min of daily socialization in a playroom. Infants paired from postnatal week 3 through month 4 developed a playroom behavioral repertoire consisting largely of mutual clinging, fear, and social withdrawal. This was especially true of females. Unlike the singly caged infants, pair-reared monkeys did not successfully adapt to living in a large social group at 8-10 months of age. In this situation, pair-reared infants were subordinate and spent almost all of their time huddling on the pen floor. It was concluded that rearing macaque infants in pairs produces a behavioral repertoire that is maladaptive with respect to social development.