Could the tears of an attacked woman calm the behavior of her attacker? After studies on rodents, the results on humans seem to point in this direction, without however proving the biological cause.
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In nature, mammals use bodily fluids (sweat, urine, etc.) to transmit social chemical signals. Tears could play this same role, although Charles Darwin seemed to find no useful function in them other than lubricating the eye. The father of the theory of evolution believed that “emotional” tears must have evolved in humans randomly.
Tears, protection against aggression?
However, many previous studies have highlighted social signals in rodent tears with the objective of reducing the animals’ aggressiveness. Thus, in fights between two male mice, tears would reduce the aggressive behavior of the dominant male towards the dominated one. In humans, research on the subject is only just beginning. Professor Noam Sobel and his team at the Weizmann Institute of Science in Israel hypothesized that human tears also contain chemicals that serve as social signals. The results of the study are published in PLOS Biology.
“ We showed that tears activate olfactory receptors and modify brain circuits linked to aggression, significantly reducing aggressive behaviorsaid Noam Sobel. These results suggest that tears are a chemical blanket, providing protection against aggression, and that this effect is common to rodents and humans. “.
Two experiments carried out on few participants
The researchers carried out two types of experiment on men exposed either to women’s tears or to control saline solutions, without being able to distinguish one from the other because they are all odorless. On one hand, six women aged 22 to 25 provided “emotional tears” after watching sad movie clips. On the other hand, 25 men were asked to sniff either solution and then participate in a money game designed to elicit aggressive behavior from one player toward another player (in thinking he was cheating). Result: players exposed to tears were 43.7% less aggressive than the others.
In the second experiment, the researchers wanted to know the effect of inhaling tears on the brain. Approximately the same number of participants underwent a functional magnetic resonance imaging (fMRI) scan with the same type of gaming experience. Functional imaging showed that two brain regions linked to aggression — the prefrontal cortex and the anterior insula — were less active when men breathed tears. Furthermore, there would be a significant correlation between the experimental condition (tears versus saline) and activity in these regions.
According to the authors, women’s tears contain an odorless chemical signal that reduces testosterone levels and associated aggression. It is important to note that these researchers start from the prerequisite that accuses a high level of testosterone of causing increased aggression in men, which could be a preconceived idea. Furthermore, the number of participants was relatively low.
