Scent of Tears May Make Men Less Aggressive

We all know tears have a tendency to produce empathy, but scientists now believe an evolutionary element is at play: their scent calms us down. Smithsonian Magazine writes that a study in Plos Biology specifically observing male aggression found that an odorless scent in teardrops collected from women prompted the brain to take it down a notch. Scientific American calls it a "chemical peacemaker" between men and women, though the researchers believe this chemosignaling goes beyond gender, and even species. "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," says study co-author Noam Sobel.

Sobel's previous research found that women's tears brought down testosterone levels in men. To further puzzle out what's happening when women cry, the researchers collected tears from female donors (which was one of the trickier parts of the experiment) and placed them, along with a set of control scents, into various "sniff jars." Male volunteers played a game often used to measured aggression while inside a magnetic resonance imaging scanner to track their brain activity, and then another round after taking a whiff from one of the jars. Aggressive play went down by 44% for those who sniffed the tears, while activity in regions of the brain regions associated with aggression and decision-making was reduced.

Next up, they hope to see how women respond to each other's tears, and what baby teardrops do to us. "Babies cannot communicate with you in language," Sobel said. "But evolution may have provided babies with this tool to lower aggression." His lab also hopes to identify the ingredient in teardrops that calms us, which could be manufactured into a substance people use to reduce aggressive tendencies. Others believe more research needs to be conducted to understand why some forms of violence aren't tamped down by this chemosignaling. "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," psychologist Dr Minna Lyons tells the Guardian. (The real Count Dracula may have cried bloody tears.)