Terrestrial mammals use pheromones to effectively trigger or block conspecific aggression. Here we tested whether hexadecanal (HEX), a human body-volatile implicated as a mammalian-wide social odor, impacts human aggression. Using validated behavioral 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 HEX as a human pheromone, whose sex-specific brain processing is at the mechanistic heart of human aggressive behavior.
bioRxiv Subject Collection: Neuroscience