Researchers Explore How Tears Influence Aggression and Brain Activity
Scientists have reported that a component found in human tears can dampen aggressive responses in others. The findings were published in Plos Biology, and they form part of a broader discussion about how crying may serve an evolutionary purpose in protecting vulnerable young children from potential harm.
The proposed theory is that tear molecules evolved, in part, to shield crying infants from aggression by others. This idea builds on previous work suggesting tear-derived compounds can influence social behavior in adults as well as infants.
In a series of experiments, researchers examined whether molecules extracted from women’s tears could modulate aggressive tendencies. The team found that tears collected from women produced measurable changes in the brains of participants and correlated with reduced aggression in specific tasks. In the language of neuroscience, these tear components appeared to alter neural pathways related to emotional regulation and impulse control. The researchers noted that the effect seemed consistent across several functional measures, though they emphasized the need for replication and deeper study .
Earlier findings from the same laboratory indicated that tear-derived substances could lower testosterone levels in men. However, it remained unclear whether hormonal changes would translate into observable shifts in behavior. The newer work sought to bridge that gap by directly testing how exposure to tear compounds would affect performance in controlled behavioral scenarios.
In the described studies, Shani Agron and colleagues recruited female participants to provide tear samples while they watched emotionally evocative films. In a controlled setting, 31 male volunteers were randomly assigned to inhale either a saline solution or tears from women. After the inhalation, the participants engaged in a computer-based task designed by psychologists to provoke competition and potential retaliation when scores were unfairly tallied against them.
The results showed a substantial reduction in aggressive responses when tears were inhaled: retaliatory behavior dropped by about 43 percent compared with the saline condition. The researchers interpreted this as evidence that tear-borne molecules can influence social behavior in real time, likely by altering brain activity in regions tied to threat processing and emotional control. The study emphasized that the effect was specific to exposure to female tears and did not occur with saline, underscoring a potential chemical signaling mechanism in human social interactions .
These findings contribute to a growing body of work exploring how biochemical signals in everyday human secretions may shape behavior, from aggression to empathy and social bonding. While the results are provocative, scientists cautioned that they represent a piece of a larger puzzle. Additional research involving larger, more diverse samples and varied emotional contexts will be needed to determine how universal and robust the tear-related effects are across populations and situations .
The researchers also highlighted the importance of ethical considerations in this line of work. If tear-derived compounds can influence behavior, researchers and clinicians must consider how such signals might be used or misused in social settings, public policy, or clinical contexts. The study’s authors suggested that future work could explore practical implications for understanding stress, aggression, and social cohesion, while continuing to investigate the underlying neural mechanisms that enable these effects .
In summary, the experiments reinforce the idea that tears do more than convey emotion. They may carry biologically active substances capable of modulating how people respond to social challenges. While this line of inquiry is still developing, the findings represent a compelling step toward decoding the biochemical language of human social behavior. Researchers stated that replication and cross-cultural studies would help clarify how tear signals operate across different groups and life stages .