Human Tears Reduce Aggression in Men, Study Finds

A recent study published in PLOS Biology has revealed that human tears contain a chemical signal that can reduce aggression in men. The research, conducted by the Weizmann Institute of Science in Israel, found that exposure to female tears led to a decrease in aggressive behavior in male volunteers.

The study involved 25 male volunteers who were exposed to either “emotional” tears or saline. The tears were collected from six female volunteers who watched sad films and captured their tears using a mirror. The volunteers were unable to distinguish between the substances, as both are clear and odorless.

The researchers then had the male volunteers play a computer game that involved accumulating money while a fictitious opponent could steal their earnings. The opportunity to take revenge on the opponent by causing them to lose money was significantly reduced after the men sniffed the tears.

This effect was similar to what has been observed in rodents, but unlike rodents, humans do not have a vomeronasal organ, which detects odorless chemical signals. To investigate further, the researchers applied the tears to 62 olfactory receptors in a lab dish and found that four receptors were activated by tears, but not saline.

The researchers then repeated the experiments with the men’s brains connected to MRI scanners. The imaging revealed that the prefrontal cortex and anterior insula, which are related to aggression, became more active when men were provoked during the game. However, the effect was not as strong if they had sniffed tears.

The study’s authors noted that crying often occurs in close-range interactions, and “kissing teary cheeks” is a recurring theme across cultures. They suggested that emitting chemical signals to prevent aggression may have been even more important among infants, where verbal communication is not possible.

The discovery of this chemical signal in human tears could have significant implications for understanding human behavior and social interactions. Further research is needed to explore the potential applications of this finding in various fields, such as psychology, medicine, and social policy.