Discussion
aggression, withdrawal behaviors
In the present study, we investigated the effects of androstadienone on reactive and proactive aggression in both men and women. At the baseline level, men exhibited stronger reactive aggression compared with women, corroborating past findings that men are more responsive to provocation (As a fundamental social behavior, aggression is vital for survival and reproduction in both sexes. However, research across species shows that it is often displayed differentially between both sexes as a result of natural selection, usually at a higher level in men than women, accompanied by differential neural circuits (On top of the sexual dimorphism in aggression, the sex-specific effect of androstadienone adds to the growing literature the sexual dimorphic nature of this chemosignal. For example, in a gender identification task where participants were asked to judge the gender of visually presented point-light walkers, smelling androstadienone biased heterosexual women, but not men, toward perceiving the walkers as more masculine (In men, androstadienone acts as a chemosignal of dominance that induces behavioral avoidance and social withdrawal behaviors. For instance, androstadienone reduces interference in the processing of angry target faces by non-relevant emotional words, suggesting androstadienone could prepare individuals for an upcoming conflict by highlighting the threatening facial expressions (Note that Preferential processing of male aggression signals has been shown in women at the neural level. Specifically, women demonstrate enhanced neural processing of human aggression sweat from men rather than that from women. The increased sensitivity to male aggression signals has adaptive value since male aggression typically targets physical harm, in particular toward women (Interestingly, for women, only reactive aggression was affected under exposure to androstadienone. First, a previous study has shown that for women, reactive aggression is related to a heightened sympathetic nervous system, while proactive aggression is associated with an augmented parasympathetic nervous system (Some issues warrant further discussion. First, previous research has shown that androstadienone has divergent effects on homosexual and heterosexual individuals (In conclusion, our findings demonstrate that while androstadienone decreases both proactive and reactive aggression in men, it increases reactive aggression in women. These data provide direct evidence that androstadienone modulates human aggression in a sex-dependent manner.