Researchers at Israel’s Weizmann Institute of Science have found a link between male aggression and women’s tears, according to a study. The report was published last week in the journal PLOS Biology and reviewed by Smithsonian.
Scientists assessed the level of aggressive behavior in 25 men as they played a video game intended to prompt antagonism. Though participants were led to believe they were playing against another human being who was cheating, they were in fact paired against a computer algorithm. Their aggression was monitored by the number of times they chose to “take revenge” against the other player, which in the context of the game meant stealing their winnings.
In the experiment’s second wave, 26 men played the same video game while inside an MRI machine that kept track of their brain activity.
During both trials, the men were given a substance to sniff that were either “emotional” female tears or a saline solution. The researchers obtained tear fluid samples from a small group of 100 women aged 22–25. It was important the tears were “emotional,” such as the ones you might shed watching a sad movie, rather than the type you would cry from chopping onions. “Unemotional” tears are composed differently, and therefore not useful for this study.
“We knew that sniffing tears lowers testosterone and that lowering testosterone has a greater effect on aggression in men than in women, so we began by studying the impact of tears on men, because this gave us higher chances of seeing an effect,” lead author Shani Agron said in the report.
Scientists found that smelling a woman’s tears reduced male aggression by up to 43.7 percent compared to the saline solution. Additionally, the prefrontal cortex and left anterior insula—two parts of the brain related to aggression—were far less active after the men had sniffed the tears. Meanwhile, activity in the amygdala, which processes emotions and smells, greatly increased.
“These findings suggest that tears are a chemical blanket offering protection against aggression—and that this effect is common to rodents and humans, and perhaps to other mammals as well,” co-author Noam Sobel wrote.
It’s an interesting result, considering that previous studies have shown similar traits in the animal kingdom. For example, the tears of female mice contain a chemical which has been shown to reduce aggression in male mice. It also goes a long way to explaining the function of tears, something that biologist Charles Darwin once called “purposeless.”
However, some say more research is needed before definitive conclusions can be drawn. Minna Lyons, a psychologist in England, called the study’s findings “remarkable” but warned tears likely have more uses than simply reducing aggression.
“In real life, things may play out differently. The tears of the target of domestic violence may do little in reducing aggression of the perpetrator. Why does the chemosignaling not work in these circumstances?” Lyons told The Guardian. “The social context of crying is massively complicated, and I suspect the reduction of aggression is just one of the many potential functions of tears.”
The researchers are hoping to widen their study to determine these other functions. They hope to examine whether women experience similar reductions in aggression from sniffing tears, and whether the tears of infants trigger the same response in adults.
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