Social status moderates the relationship between facial structure and aggression.

A growing body of evidence has linked individual differences in facial structure-in particular, the facial width-to-height ratio (FWHR)-to social behaviors, including aggression, cheating, and nonreciprocation of trust. In the research reported here, we extended this work by demonstrating that the association between FWHR and aggression is moderated by subjective and objective measures of social status. In Study 1 (N = 237 college students), FWHR was positively correlated with aggressive behavior, but only among men reporting relatively low social status. In Study 2 (N = 891 professional hockey players), FWHR was positively correlated with penalty minutes, but only among players who earned relatively low salaries. Collectively, these studies provide compelling evidence for the role of social status in moderating the relationship between facial structure and aggression, indicating that FWHR is a robust predictor of aggressive behavior, but only in the context of relatively low social status.

Testosterone, cortisol, and psychopathic traits in men and women.

Cortisol and testosterone are theorized to independently and jointly influence antisocial behaviors. The current research examined the independent and interactive effects of baseline testosterone and cortisol on individual differences in psychopathic traits in a relatively large non-clinical sample (N=237). Participants completed the Self-Report Psychopathy - Short Form (SRP; Paulhus, Neumann, & Hare, in press) and provided saliva samples. Analyses indicated that testosterone and cortisol were positively correlated with psychopathic traits in men, but beyond these effects, cortisol moderated the relationship between testosterone and psychopathy in men. The relationship between testosterone and psychopathy within men was positive when cortisol levels were high, but negative when cortisol levels were low. These results have implications for work surrounding the dual hormone hypothesis and suggest that nonclinical variability in psychopathy can be predicted by baseline testosterone and cortisol.

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.