People’s empathy for one another is frequently sparked by tears. However, a recent study indicates that they might have many effects: Men’s hostility may decrease when they smell women’s tears, which suggests that the emotional reaction serves a protective function. Researchers measured men’s levels of violent behavior and brain activity, and found that men’s hostility decreased by almost 40% after smelling women’s tears.

According to the scientists, this conclusion—which was published in PLOS Biology last week—may apply to all human tears.
Co-author Noam Sobel, a neurobiologist at the Weizmann Institute of Science in Israel, states in the study that “tears are a chemical blanket offering protection against aggression—an effect common to rodents and humans, and perhaps to other mammals as well,” says the statement.

While the field of human chemosignaling has received little attention, Sobel’s lab has previously shown that men’s testosterone levels, physiological markers of arousal, and self-reported sexual excitement were all decreased by women’s tears.

Lead author of the study Shani Agron of the Weizmann Institute states in a statement, “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.”

People are able to detect a wide range of scents and chemicals that other people release that serve as social indicators, frequently without realizing it. There is evidence to support the notion that perspiration can also transmit emotional information, and previous study has suggested that people may smell dread and worry in others. There is also chemical communication between species: dogs seem to be able to detect chemosignals from humans that represent a range of emotions, including fear and happiness.

The authors obtained “emotional” tears from six female donors, ages 22 to 25, in order to investigate the role that tears play in this. Of the more than 100 volunteers, only the members of this small sample group were able to produce enough tears for the study. Sobel told Rachel Nuwer of Scientific American that the team’s struggle with tear collection stemmed from the requirement to gather “a lot of tears,” or at least one milliliter, for every male participant. Moreover, the watery droplets could not have been produced by the majority of participants’ manner of chopping onions, which produces a different kind of tear than does watching depressing movies.

The subjects were not informed of what they were smelling when they smelled either saline solution or female tears, both of which have no smell. Compared to the saline control, the men behaved 43.7 percent less aggressively after smelling the women’s tears. Furthermore, according to Scientific American, when men scented the tears, there was a significant decrease in activity in two brain regions linked to anger and decision-making: the prefrontal cortex and left anterior insula. Additionally, there was an increase in connections to the amygdala, the area of the brain in charge of emotions and smell.

In future research, the team hopes to examine whether human women display similar reductions in aggression after tear-sniffing and whether babies’ tears could produce a similar response in adults.