Humans emit a compound called hexadecanal (HEX for short) from their skin, saliva, and feces. Newborns release copious amounts of the compound from their heads. Even though HEX has no discernible scent, it can affect the behavior of those who smell it, according to research conducted by Noam Sobel, a neuroscientist at the Weizmann Institute of Science.
Several experiments have shown that women exposed to the chemicals become more aggressive, whereas men become more passive.
In one task, participants negotiated with an unseen partner to divvy up a sum of virtual money. The participants thought they were playing with another person, but they were actually playing against computers. If a player offered their "partner" anything less than 90% of the whole amount, the computer rejected their proposals with a bright red "NO!" preventing them from earning any money.
Next, participants played a game in which they earned opportunities to blast that same "partner" with noise. Players could choose how loud the blasts were by selecting buttons that bore emojis expressing varying levels of pain—and in doing so, displayed their varying levels of aggression.
Sniffing HEX did not calm all the participants down, but had different impacts on men and women, the team reports today in Science Advances. Women exposed to the chemical behaved 19% more aggressively in the noise-blast task, whereas men were 18.5% less aggressive.