But "it makes sense," she said in an interview. "In the beginning, I found it a little bit far-fetched," said neuroscientist Jessica Freiherr at Friedrich-Alexander University, who was not involved with the research.
And the authors noted that they didn't know if the amount of HEX their subjects smelled was the same as what they would get from sniffing babies' heads. There are still plenty of questions to answer. This region seemed to turn connections to brain regions that control aggression up or down, depending on the subject's gender. And they saw that HEX activated a part of the brain involved in judging social interactions. So they did another experiment, this time testing subjects' reactions while in a brain scanner. "I said, 'OK, it's plausible,' " he added. "If you're an offspring, you have a vested interest in emitting a molecule that will make women more aggressive and men less aggressive." "This was totally 100% Eva's eureka moment," Sobel said. "I personally did not see any possible ecological reason for a molecule to increase aggression in women and decrease it in men."īut lead author Eva Mishor, who was studying signals of aggression for her doctorate at the Weizmann Institute, noted that in animals, female aggression is usually aimed at defending their young, while male aggression is often directed at the offspring themselves. The first time he saw the results, they "made absolutely no sense to me," co-author Noam Sobel, head of the neurobiology department at the Weizmann Institute of Science, said in an interview. On a six-point scale, the differences were, on average, roughly between half a point and less than a point in either direction.
When players sniffed HEX before playing, women's blasts were louder and men's were quieter. The louder the noise, the higher the scientists rated the player's aggression level. In one game, when the aggravated player is allowed to win, he or she gets to blast the opponent with a loud noise. The study tested people's responses to HEX using rigged games designed to aggravate the player. They also discovered that HEX is the most abundant of the many chemicals babies' heads give off. It's also found in feces, and raising babies is "the one social setting where humans have extensive exposure" to poo, the authors note. In the latest study, scientists tested how people responded to a chemical called hexadecanal, or HEX. But scientists are increasingly finding that odors affect us more than we think. We humans like to think we are above all that. Mice whose sense of smell is damaged don't attack other mice intruding on their territory. A rabbit mom will attack her pups if they smell like another female rabbit.
Odors affect behavior in the animal world in plenty of ways. It could be a chemical defense system we inherited from our animal ancestors, the authors speculate, making women more likely to defend their babies and men less likely to kill them. A chemical that babies give off from their heads calms men but makes women more aggressive, according to new research in the journal Science Advances.