Men are less aggressive after smelling women's tears, according to a study published in PLOS Biology .
The research, conducted by the Weizmann Institute of Science in Israel, found that human tears contain a chemical signal that reduces activity in two brain regions associated with aggression.
Previous studies with rodents found that the tears of female mice reduce fights between male mice. The scientists said other studies also show that smelling tears reduces testosterone.
After collecting tears from six female volunteers who watched sad movies, the researchers exposed dozens of men to tears or a saline solution. They could not tell the difference between the liquids as they are both clear and odorless.
The men then played a computer game, used in other studies on aggression (in the game they collect money, while the opponent in the game tries to steal it from them). After smelling women's tears, men's desire to retaliate in the game dropped by 43.7%.
These results are similar to those of the rodent study, but unlike rodents, humans do not have a structure in the nose that detects non-odor chemical signals. The researchers dug deeper by studying 62 olfactory receptors, which play a key role in the sense of smell, finding that four were activated by tears.
Dr. Minna Lyons, a psychologist at Liverpool John Moores University, told the Guardian that the data is "remarkable", but people should not draw significant conclusions.
"In real life, things can develop differently. Tears as a result of domestic violence can do little to reduce the aggressiveness of the abuser," she said. "The social context of crying is extremely complex, and I suspect that reducing aggression is only one of many possible functions of tears."
