- Human tears inhibit male aggression
- Chemical signal discovered in tears
- Emotional crying’s evolutionary purpose explored
A study has discovered that human tears contain a chemical signal that inhibits aggression in males.
A pair of men were instructed to inhale either the emotional tears of women or saline, which is a solution of sodium and water, as they participated in a two-person game.
The objective of the game was to provoke combative conduct from the other participant, whom the male players were duped into believing was deceiving.
If presented with the chance, the male individuals might exact vengeance on the opponent by inflicting financial loss upon them.
After men inhaled women’s emotional sobbing, vengeful behaviour dropped by over 40% during the game.
Imaging performed repeatedly in an MRI scanner revealed that the prefrontal cortex and anterior insula, two regions of the brain associated with aggression, became more active when the men were provoked during the game, but not when they were inhaling the tears.
The study contributes to the resolution of the enduring enigma surrounding the causes of human tears, according to the researchers.
Charles Darwin was perplexed by emotional crying, which seemed to serve no purpose other than to lubricate the eye. Partisans concluded that the evolution of crying in Homo sapiens must have occurred by coincidence.
However, subsequent research has demonstrated that the tears of specific mammalian species, predominantly rodents, comprise chemical messengers. These messengers are capable of emitting themselves as social cues.
Research has shown that the presence of female tears inhibits aggression in male rodents. Smearing subordinate blind mole rat males in tears can diminish dominant male aggression.
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The Weizmann Institute of Science in Israel team published in the journal Plos Biology, “We discovered that human tears, like those of mice, contain a chemical signal that inhibits conspecific male aggression.”
This challenges the assumption that emotional emotions are an exclusively human experience.
Shani Agron noted that the effect is greatest when vocal communication is forbidden, such as with infants.
“Since infants are unable to communicate verbally, responding to chemical signals to defend themselves against aggression can be crucial,” she explained.
Future research, according to the team, will investigate whether the findings of the study also apply to women.
The research was directed by Professor Noam Sobel, who stated, “We have demonstrated that tears alter aggression-related brain circuits and activate olfactory receptors, thereby substantially reducing aggressive behaviour.”
These results indicate that tears serve as a chemical blanket that protects against aggression. Furthermore, this effect may be shared by humans, rodents, and possibly other mammals.
In 2011, Professor Sobel’s research group demonstrated that men experienced a moderate reduction in sexual arousal as a result of sniffing women’s emotive tears, which led to a decrease in testosterone levels.
According to recent research, canines also exhibit emotional weeping.
Further investigation is required to ascertain whether these tears contain chemical signals that humans or other canines can detect.
