Long-term effects of early mothering behavior on responsiveness to the environment in vervet monkeys.

The long-term effect of early mothering style on juvenile responsiveness to the external environment was studied in vervet monkeys living in two naturally composed, undisturbed social groups. Mothering behavior for 35 mother-infant dyads was analyzed by principal components analysis which revealed two independent dimensions: protectiveness and rejection. Protectiveness was characterized by high levels of approach, making contact, restraint, and inspection from mother to infant, and rejection was associated with high levels of rejection, breaking contact, and leaving. When observed as yearlings and 2-year-olds, juveniles who had had more protective early mothering showed less interest in the external environment, as measured by the percentage of time they spent looking outside the home enclosure. They also took longer to enter a completely novel environment compared to juveniles who had had less protective mothers. Maternal rejection was not significantly associated with looking out or with latency to enter the novel environment. These results were independent of the effects of age, sex, and dominance rank on behavior.