Researchers have discovered that human tears contain a substance capable of reducing aggression, suggesting that tears may have evolved to protect vulnerable infants. The study conducted by the Weizmann Institute of Science in Israel found that sniffing emotional tears from women reduced male aggression by more than 40% in computerized tests.

“Noam Sobel, a professor of neurobiology at the Weizmann Institute of Science in Israel, stated, ‘The reduction in aggression was impressive to us, it seems real. Whatever is in tears actually lowers aggression,’” the study reports.

Previous research at Sobel’s lab revealed that sniffing women’s tears reduced male testosterone. However, it was unclear if this hormonal change affected behavior. The current study involved collecting tears from women watching sad movies, and the experiments with 31 men showed a 43.7% reduction in aggressive behavior when exposed to women’s tears compared to saline.

The scientists also conducted brain scans, revealing that those who sniffed tears exhibited increased functional connectivity between scent-handling regions and lower activity in aggression-related brain networks. Sobel noted that this substance seems to orchestrate the brain’s response to aggression.

Despite the chemical’s potential impact on reducing aggression, Sobel acknowledges that it might not significantly influence adult social interactions. However, he speculates that tears may have evolved to protect vulnerable infants who cannot communicate their needs effectively.

Dr. Ad Vingerhoets, an emeritus professor, mentioned that it makes sense for tears to inhibit aggression, especially in the context of infants who cry a lot and are at risk of physical abuse. Dr. Minna Lyons from Liverpool John Moores University emphasized the need for replication of studies on human behavior and highlighted the complexity of the social context of crying.

Sobel’s lab aims to identify the active ingredient in tears, potentially paving the way for manufacturing the substance and using it to reduce aggressive tendencies. The findings suggest a fascinating evolutionary aspect to human tears, hinting at a protective role for the vulnerable, especially infants.