Long-term follow-up of previously separated pigtail macaques: group and individual differences in response to novel situations.

A follow-up study of monkeys who experienced maternal separations as infants 2.5-4.9 years earlier was performed. Matched pairs of previously separated and nonseparated control monkeys were observed individually in four unfamiliar situations, and their behavioral responses and plasma cortisol levels were measured. Results indicated that previously separated animals displayed more disturbance than did their matched controls, and levels of disturbance were significantly correlated with the degree of behavioral and physiological disturbance displayed during the original maternal separations. The results support the idea that the perception of the maternal separation may be a significant factor in whether long-term behavioral deficits exist in social and emotional functioning.