Can smelling tears reduce aggression? – 12/24/2023 – Balance

Crying can have a calming effect, everyone knows that. But a study published last Thursday (21) in the American scientific journal PLOS Biology suggests that human tears, through a chemical signal, also reduce brain activity linked to aggression.

The research, which included tests in which tears were inhaled, was carried out by the Weizmann Institute of Science, in Israel. The samples were collected from women — this was simply because they volunteered as participants. However, according to the study authors, it is very likely that the effect is not just related to females.

According to researchers, tears are a mammalian mechanism that provides a kind of “protective chemical blanket” against aggression.

The study was preceded by others, carried out with animals. “Rodent tears contain social chemical signals with diverse effects, including blocking male aggression. Human tears also contain a chemical signal that reduces male testosterone, but its behavioral significance is unclear,” the authors explain.

In the animal world, female mice use tears to reduce fights between males. And males of the naked mole rat species use their own tears to reduce attacks from other males.

Blocking aggression in men

In the Israel study, a team led by Shani Agron exposed 25 male volunteers to “emotional” tears or a saline solution. The volunteers did not know what they were inhaling, as both substances were transparent and odorless. Real tears were obtained from six female volunteers, who individually watched films with sensitive or sad content.

“When we looked for volunteers who could donate tears, we found mainly women, as it is more socially accepted for them to cry”, explains Agron.

The research team wanted to demonstrate the effect of tears on men. “Reduced testosterone is associated with reduced aggression, so we tested the hypothesis that human tears act like rodent tears to block male aggression,” they report.

“Reducing testosterone has a greater effect on aggression in men than in women,” adds Agron.

Revenge and aggressive behavior

The study analyzed volunteers’ behavior through a computer game, which involved accumulating money while a fictional opponent stole their winnings. The research concluded that revenge seeking and aggressive gaming behavior decreased by 43.7% after men smelled tears.

Scientists also analyzed the impact on behavior using brain and MRI scanners.

The images revealed that the prefrontal cortex and anterior insula, which are related to aggression, were more activated when the men were provoked during the game, but the effect was not as strong when they inhaled tears.

“In short, our results show that, as in rodents, a chemical signal linked to human tears reduces male aggression, a mechanism that depends on the structural and functional overlap of the brain substrates of smell and aggression,” the researchers conclude.