The Kids Are Alright: Maternal Behavioral Interactions and Stress Reactivity in Infants of Differentially Reared Rhesus Monkeys

Behavioral interactions and infant stress reactivity were investigated in 120 mother-infant pairs of rhesus monkeys (Macaca mulatta). The mothers themselves were either mother-reared (MR), surrogate-peer reared (SPR), or peer-reared (PR). Focal observations and isolation stress tests were conducted throughout post-natal months 1–6 of the infants’ lives, followed by a standardized 4-week social separation regimen. PR mothers engaged in more grooming than MR mothers during months 4 and 6, and more rejections than both other groups during months 3 and 5. Although all infants were mother-reared, D 14 and 30 cortisol responses in infants of MR and SPR mothers resembled their mother’s responses at that age, a pattern that corresponded inversely with levels of mother-infant mutual ventral contact during month 1. Despite observed differences in maternal behavior and evidence of non-genomic cross-generational transmission of early cortisol reactivity, infant stress responses throughout later infancy did not vary as a function of the mother’s rearing condition. Maternal Behavioral Interactions and Stress Reactivity in Infants of Differentially Reared Rhesus Monkeys The impact of early adverse experience on biobehavioral development in humans and other animals is well documented. Extensive evidence from the human literature 103 04--Roma--103-122 8/7/06 12:50 PM Page 103