Sniffing women’s tears makes men less aggressive, bizarre study finds

A study found that human tears contain a chemical signal that prevents aggression in men.

They had a group of men smell women's emotional tears or saltwater—a mixture of salt and water—while they played a game of twos.

The game was designed to provoke aggressive behavior against the other player, who the men believed was cheating.

When given the opportunity, men can take revenge on the other player by causing them to lose their money.

Aggressive, revenge-seeking behavior during a match decreased by more than 40 percent after men inhaled women's emotional tears.

When repeated using an MRI scanner, the imaging showed that two areas of the brain associated with aggression — the prefrontal cortex and the anterior insula — became more active when the men were provoked during the game, but did not become active in the same situations when the men were inhaling tears.

Researchers say the study helps address the long-standing mystery of why we cry.

Charles Darwin was puzzled by emotional crying, which seemed to have no useful function beyond the role that tears play in lubricating the eyes – so he concluded that crying must have evolved in humans by chance.

But since then, studies have shown that the tears of some mammals — especially rodents — contain chemicals that act as social signals that can be emitted on demand.

Aggression in male rodents has been found to be suppressed when they smell the tears of females, while male subordinate blind mole rats smear themselves with tears to reduce the aggressive behavior of the dominant male towards them.

“We found that, as in mice, human tears contain a chemical signal that inhibits certain male aggression,” the team from the Weizmann Institute of Science in Israel said in the journal Plos Biology.

“This flies in the face of the idea that emotional tears are uniquely human.”

Researcher Shani Agron said the effect is likely to be more significant when verbal communication is impossible, for example, in interactions with children.

“Infants cannot talk, so responding to chemical signals to protect themselves from aggression may be crucial for them,” she added.

The team said their future research will explore whether the study's findings also apply to women.

Professor Noam Sobel, who supervised the research, said: We have shown that tears activate olfactory receptors and that they change brain circuits associated with aggression, significantly reducing aggressive behavior.

“These findings suggest that tears are a chemical covering that provides protection against aggression – and that this effect is common in rodents and humans, and perhaps in other mammals as well.”

In 2011, Professor Sobel's team showed that inhaling women's emotional tears reduces men's testosterone levels, resulting in somewhat lower levels of sexual arousal.

Recent studies have found that dogs shed emotional tears, too.

However, more research is needed to determine whether these tears contain chemical signals that can be picked up by other dogs or humans.

Experts from Duke University School of Medicine also participated in the study.