NATURE NEEDS NURTURE - THE INTERACTION OF HORMONAL AND SOCIAL INFLUENCES ON THE DEVELOPMENT OF BEHAVIORAL SEX-DIFFERENCES IN RHESUS-MONKEYS

Thirty years of research on early social and hormonal environments and their relationship to the expression of behavioral sex differences in rhesus monkeys are reviewed. These studies demonstrate that whether a ggressive and submissive behaviors are sexually dimorphic depends prim arily on the social and not the hormonal environment. Early rearing en vironments without mothers or allowing brief periods of peer interacti on produced higher levels of male aggression and female submission. Pr esenting behavior was expressed more by females than males in environm ents with high male aggressivity and female submissiveness. No sex dif ferences in presenting occurred in low aggressivity environments, unle ss monkeys were reared isosexually, when males presented more than fem ales. Rough and tumble play and foot-clasp mounting were consistently exhibited more by males than females across all rearing environments s tudied, but rearing environment affected the degree of the sex differe nce. When reared isosexually males displayed less, and females more, f oot-clasp mounting than when heterosexually reared. No social environm ent increased the low frequency of female rough and tumble play. Suppr essing neonatal androgen in males did not effect any sexually dimorphi c behavior. Prenatal androgen administration to genetic females mascul inized many aspects of their juvenile behavior, consistently increasin g rough and tumble play and foot-clasp mounting across different socia l environments. Thus the sexually dimorphic behaviors which showed the smallest variability across social contexts were the most profoundly affected by the prenatal hormonal environment. These studies demonstra te that the expression of consistent juvenile behavioral sex differenc es results from hormonally induced predispositions to engage in specif ic patterns of juvenile behavior whose expression is shaped by the spe cific social environment experienced by the developing monkey. (C) 199 6 Academic Press.