Human Study Unveils Striking Reduction In Aggression Through Social Chemosignaling

A recent study, released on December 21st in the open-access journal PLOS Biology, discloses that chemicals found in women’s tears possess the remarkable ability to curb aggression in men.

Spearheaded by Shani Agron at the Weizmann Institute of Science, Israel, the research establishes a connection between sniffing tears and reduced brain activity associated with aggression, subsequently resulting in diminished aggressive behavior.

Drawing inspiration from the documented effects in rodents, where male aggression diminishes upon exposure to female tears, the study explores the concept of social chemosignaling in humans.

While prevalent in the animal kingdom, this phenomenon is less explored in the context of human behavior.

Dramatic Reduction in Aggression Through Social Chemosignaling

To investigate whether tears exert a similar impact on people, the researchers conducted a controlled experiment involving men exposed to either women’s emotional tears or odorless saline during a two-person game designed to elicit aggressive responses.

In the game, participants were led to believe that the other player was cheating, providing them with an opportunity for revenge by causing monetary losses. Unaware of what they were sniffing, the men could not distinguish between tears and saline.

Astonishingly, revenge-seeking aggressive behavior in the game plummeted by more than 40% after exposure to women’s emotional tears.

Functional imaging using an MRI scanner revealed that two brain regions associated with aggression—the prefrontal cortex and anterior insula—became less active when men sniffed tears in situations provoking aggression.

The greater the difference in this brain activity, the less frequently the players sought revenge during the game.

This groundbreaking link between tears, altered brain activity, and reduced aggressive behavior suggests that social chemosignaling is a contributing factor to human aggression, challenging the perception that emotional tears are exclusively human.

The authors conclude, “We found that, similar to mice, human tears contain a chemical signal that inhibits male aggression toward conspecifics. This contradicts the notion that emotional tears are a uniquely human trait.”