Androgens and behaviour

Abstract

This paper reviews findings from a number of studies designed to assess the joint contribution of hormonal and social factors to sexual and aggressive behaviours. Studies with male rhesus monkeys have shown that exposure to receptive females results in increased plasma testosterone and copulatory behaviour, while defeat experiences with or without wounding result in decreased testosterone and a decrease in all forms of social behaviour. Studies of human males under conditions of combat threat or arduous training show parallel androgen suppression and a decrease in covert use of sexual imagery. However, the data are generally strongest in studies involving environmental manipulation with nonhuman primates and highlight considerable individual dissociation between androgen levels and sexual or aggressive behaviours. This lack of concurrence for individual animals can be understood in terms of differences in social factors such as status within the group and the seasonal nature of social relationships. Male rhesus monkeys show a significant increase in testosterone during the breeding season, but the frequency of their sexual behaviour appears largely determined by dominance rank in the group. Similarly, males show testosterone increases when introduced to a group of females, but frequency of sexual behaviours depends largely upon the females’ acceptance of the males as a more dominant member of the group. Little behavioural change after HCG induced testosterone increase in males with a constant social structure lends further credence to the importance of social factors in determining sexual and aggressive behaviours. Studies with rhesus male adolescents suggest that sexual and aggressive behaviours increasing during the third and fourth years may not parallel the increase in testosterone, although these behaviours appear to be influenced by changing androgen secretion. In humans, however, data relating androgens with sexuality and aggression are largely inconclusive. Thus while androgens may permit the expression of sexual or aggressive behaviours, the actual occurrence of such behaviours seems to depend on other factors, particularly on the relationship of an individual animal with other members of the group. A focus of interest on such psychosocial variables in addition to biological parameters is suggested for future research.