No abstract

Previous research demonstrates that prenatal testosterone exposure increases aggression, possibly through its effects on the structure and function of neural circuits supporting threat detection and emotion regulation. Here we examined associations between regional gray matter volume, trait aggression, and the ratio of the second and fourth digit of the hand (2D:4D ratio) as a putative index of prenatal testosterone exposure in 464 healthy young adult volunteers. Our analyses revealed a significant positive correlation between 2D:4D ratio and gray matter volume of the dorsal anterior cingulate cortex (dACC), a brain region supporting, emotion regulation, conflict monitoring, and behavioral inhibition. Subsequent analyses demonstrated that reduced (i.e., masculinized) gray matter volume in the dACC mediated the relationship between 2D:4D ratio and aggression in women, but not men. Expanding on this gender-specific mediation, additional analyses demonstrated that the shared variance between 2D:4D ratio, dACC gray matter volume, and aggression in women reflected the tendency to engage in cognitive reappraisal of emotionally provocative stimuli. Our results provide novel evidence that 2D:4D ratio is associated with masculinization of dACC gray matter volume, and that this neural phenotype mediates, in part, the expression of trait aggression in women.

Testosterone (T) concentrations change rapidly in the context of human competition, and these changes in neuroendocrine function may serve to modulate future aggressive behavior. However, an increase in T during competition does not translate into aggressive behavior among all individuals. Here, we examined the extent to which individual differences in trait anxiety moderate the relationship between T responses to competition and aggressive behavior. Across two studies, we found that T responses to competition were positively correlated with subsequent aggression, but only among men scoring relatively low in trait anxiety. Trait anxiety did not moderate the relationship between T reactivity and aggression in women. These findings highlight the importance of considering individual difference in trait anxiety when examining the neuroendocrine correlates of human aggression.