Women's tears contain scent-borne chemicals that block aggression in men, according to research published in the journal PLOS Biology.
Smelling those tears leads to reduced brain activity related to aggression, which results in less aggressive behavior, researchers said.
Prior research has shown that male aggression in lab rats can be blocked by the scent of female tears. This sort of scent-based communication is called "social chemosignaling."
To see if the same is true in humans, researchers designed an experiment in which two men would play a game designed to elicit aggressive behavior.
One player was led to believe that the other was cheating, and were given the opportunity to get revenge by causing them to lose money, researchers said.
During these scenarios, the men were randomly exposed to either a woman's emotional tears or a placebo dose of saline solution. The men didn't know what they were sniffing, since both tears and saline are odorless.
Revenge-seeking aggressive behavior dropped more than 40% when the men sniffed female tears, compared to saline.
"We found that just like in mice, human tears contain a chemical signal that blocks conspecific male aggression," wrote the researchers led by Shani Agron, a member of the Weizmann Institute of Science's Department of Brain Sciences in Rehovot, Israel. "This goes against the notion that emotional tears are uniquely human."
Researchers repeated the experiment in an MRI brain scanner, and found that two aggression-related brain regions became more active when the men were provoked during the game.
But those same regions -- the prefrontal cortex and anterior insula -- did not become as active if the men were sniffing women's tears.
The greater the difference in this brain activity, the less often the player took revenge during the game, researchers found.
Source: Dennis Thompson, HealthDay News
