Changes in testosterone mediate the effect of winning on subsequent aggressive behaviour.

Testosterone concentrations rise rapidly in the context of competitive interactions and remain elevated in winners relative to losers. Theoretical models suggest that this divergent neuroendocrine response serves to mediate future dominance behaviours. Although research in animal models provides compelling support for this model, evidence for its applicability to human social behaviour is limited. In the current study, men and women were randomly assigned to experience a series of victories or defeats, after which aggressive behaviour was assessed using a well-validated behavioural measure. Winning produced elevated testosterone concentrations relative to losing in men, but not women. More importantly, testosterone reactivity to competition mediated the effect of winning on subsequent aggressive behaviour in men, but not women. We discuss limitations of the current study (e.g., the status manipulation may have affected other variables not measured in the study including competitiveness and physical activity expended), as well as discuss a potential neural mechanism underlying the effect of testosterone reactivity on aggressive behaviour.