It is a well-known fact that the hormone oxytocin plays an important role in pro-social behavior. It promotes the formation of attachment between mother and child, pair bonding, disposes a person to trust and benevolence toward those they consider “their own,” helps establish relationships between people, and so on. The hormone vasopressin also plays an important role in pro-social behavior, including the formation of paternal love for children.
These hormones are often called regulators of aggression. It is believed that in intra-group relations, oxytocin promotes the establishment of altruism and non-violence, which unite and coordinate the actions of individual group members. Conversely, in the case of inter-group relations, this only increases aggressiveness, as a cohesive group is ready to fight more fiercely against other “alien” groups, toward whose members oxytocin does not dispose one to trust. This is often used to explain the occurrence of wars between different groups of people [1].
At the same time, based on the theory of the violence inhibition mechanism, in species where it is strongly expressed, including humans, the restraint of aggression extends to all intra-species relations. Nevertheless, the violence that does occur is explained by the presence of a small number of individuals in whom this mechanism is impaired. This conclusion is supported by many studies, including military ones. They show that most people experience strong resistance to harming others and committing murder. Even on the battlefield, this applies to the majority of soldiers, and only a minority of them constitute the driving force of war [2].
Having two such explanations for the nature of social and aggressive behavior, the question arises as to which one is correct, or if both are correct, how they relate to one another. Answering such a question is not so difficult if one looks at how the corresponding neurophysiological systems work and interact with each other.
Recall that the use of certain agonists of serotonin 1A and 1B receptors (drugs that activate them) led to the suppression of attacking aggression in animals, while not affecting defensive aggression or other forms of behavior and social communication. This result is completely consistent with the expected result of the work of a violence inhibitor, which speaks to its function as part of the serotonergic (5-HT) system.
It is interesting that the 5-HT system, including 1A and 1B receptors, is involved in the regulation of oxytocin and vasopressin secretion [3]. In one experiment, the use of a 1A receptor agonist in mice promoted not only the suppression of attacking aggression but also the emergence of pro-social behavior (close contact and grooming of a conspecific) due to oxytocin secretion. At the same time, the simultaneous administration of an oxytocin receptor antagonist (a drug that blocks it) did not reduce the anti-aggressive effect at all, but only suppressed the pro-social behavior. And administration together with a vasopressin receptor antagonist changed nothing at all [4].
It can be concluded that the regulation of aggression and the stimulation of pro-social behavior are functions performed by different neurophysiological systems. Moreover, the 5-HT system, responsible for the former, is capable of influencing the operation of oxytocin and vasopressin receptors, responsible for the latter, but not vice versa. This means that it is precisely the theory of the violence inhibition mechanism that explains the nature of aggression regulation, while oxytocin relates only to pro-social behavior. And the absence of such behavior in an individual—for example, when encountering a “stranger” (but a representative of their own species) or simply due to the impairment of the oxytocin receptor, while the violence inhibitor is still functioning—absolutely does not mean that they will be predisposed to a violent attack.
1. De Dreu C. K. W. et al. (2010). The Neuropeptide Oxytocin Regulates Parochial Altruism in Intergroup Conflict Among Humans;
2. Theory of Violence: https://antiviolence.io/ru;
3. Jørgensen, H., Riis, M., Knigge, U., Kjaer, A., & Warberg, J. (2003). Serotonin Receptors Involved in Vasopressin and Oxytocin Secretion;
4. Tan, O., Martin, L. J., & Bowen, M. T. (2020). Divergent pathways mediate 5-HT1A receptor agonist effects on close social interaction, grooming and aggressive behaviour in mice: Exploring the involvement of the oxytocin and vasopressin systems.
