"NATURE VS. NURTURE IN MONKEYS"
Recent research has disclosed marked individual differences in patterns of biobehavioral development exhibited by rhesus monkeys across the life span. For example, approximately 5-10% of rhesus monkeys growing up in the wild consistently exhibit impulsive and/or inappropriately aggressive responses to mildly stressful situations throughout development; those same individuals also show chronic deficits in their central serotonin metabolism. These characteristic patterns of biobehavioral response emerge early in life and remain remarkably stable from infancy to adulthood. Laboratory studies have demonstrated that although these characteristics are highly heritable, they are also subject to major modification by specific early experiences, particularly those involving early social attachment relationships. For example, a specific polymorphism in the serotonin transporter gene is associated with deficits in serotonin metabolism, extreme aggression, and excessive alcohol consumption among monkeys who have experienced insecure early attachment relationships but not in monkeys who have developed secure attachment relationships with their mothers during infancy.