Sniffing the Human Body-Volatile Hexadecanal Blocks Aggression in Men but Triggers Aggression in Women

Abstract

Body-volatiles can effectively trigger or block conspecific aggression in terrestrial mammals. Here we tested whether hexadecanal (HEX), a human body-volatile implicated as a mammalian-wide social cue, impacts human aggression. Using validated behavioural paradigms, we observed a remarkable dissociation: sniffing HEX blocked aggression in men, but triggered aggression in women. Next, using functional brain imaging, we uncovered a pattern of brain activity mirroring behaviour: In both men and women, HEX increased activity in the left angular gyrus, an area implicated in perception of social cues. Hex then modulated functional connectivity between the angular gyrus and a brain network implicated in social appraisal (temporal pole) and aggressive execution (amygdala and orbitofrontal cortex) in a sex-dependent manner consistent with behaviour: increasing connectivity in men, but decreasing connectivity in women. These findings implicate sex-specific social chemosignaling at the mechanistic heart of human aggressive behaviour.