From the theory of the violence inhibition mechanism, we know that a healthy individual, when observing the suffering (distress signals) of another person, begins to experience a feeling of aversion and becomes predisposed to ceasing aggressive actions toward them. This effect is psychological; the neural pathways responsible for it are activated as a result of observing suffering as a social signal. At least, this is what we used to believe. However, some new discoveries indicate that the impact of certain distress signals on the violence inhibitor—specifically, crying—may be chemical in nature.
Several years ago, a study on rats revealed that rubbing female tears onto the face and other body parts of males, who played the role of “intruders” in the experiments, reduced the aggressiveness of the “residents”—the males whose cages they entered. Given that all necessary conditions of the resident-intruder paradigm are met, an aggressive attack by the resident on the intruder is expected. However, it was found that if the intruder smells of female tears, no aggression is shown toward them. At the same time, male tears do not possess this effect.
Recently, a similar result was reproduced in humans. To measure the aggressiveness of men, a money game was used involving provocations and the possibility to “get revenge” for them, without receiving any personal benefit from the revenge. Players were told they were playing against another person, although they were actually playing against a computer. Before the game, men were given 1 ml samples to smell 13 times at intervals of 35 seconds. The first three times it was a saline solution; the remaining ten were also saline solution for the control group and female tears for the experimental group.
As a result, aggressive gaming behavior (the desire to avenge provocations) in men who smelled female tears was 43.7% lower than in the control group. Additionally, MRI scans revealed that their prefrontal cortex and the anterior part of the insular cortex in the brain were not as strongly activated as a result of provocations during the game.
Of course, as psychologists note, certain questions may arise in real-life situations—for example, why tears, despite the remarkable results of the experiments, do not always play a significant role in stopping domestic violence. There is a suggestion that tears may not be significant in relationships between adults, and that the evolutionary role of their anti-aggressive effect is to protect children, who are unable to state that aggression must stop but will cry a lot if it occurs. Experiments with children’s tears are still planned. Research is also planned to find the specific component of tears that causes the anti-aggressive effect. This could help in the creation and production of a highly effective, humane means of self-defense that causes no harm to the attacker.
