Oxytocin influences moral emotions and decisions, study shows

A recent study in Molecular Psychiatry found that using an oxytocin nasal spray can make people feel more guilt and shame and less willing to harm others, even if it could lead to benefits. The findings contrast oxytocin’s effects with vasopressin, another neuropeptide involved in social behavior, which did not show similar results. These outcomes underscore oxytocin’s potential in addressing social and moral behavior irregularities, including those observed in certain psychiatric conditions.

Oxytocin and vasopressin are hormones that play key roles in regulating social behavior and emotional responses in humans and animals. Often referred to as the “love hormone,” oxytocin is associated with bonding, trust, empathy, and prosocial behaviors like cooperation and generosity. It is released naturally during activities such as hugging, childbirth, and breastfeeding, helping to strengthen social connections.

Vasopressin, on the other hand, is often linked to aggression, territorial behavior, and responses to stress. While it also has prosocial effects in certain contexts, its role is more complex and can vary depending on gender and social environment.

Both hormones are produced in the hypothalamus, a part of the brain that regulates essential functions, and they interact with brain systems that influence emotions, decision-making, and behavior. Researchers have long been interested in how these hormones affect not only social behaviors but also moral decision-making—choices about right and wrong that often involve empathy, guilt, and consideration for others.

Since oxytocin tends to enhance empathy and reduce aggression, and vasopressin can increase aggression in some scenarios, understanding their distinct effects on moral emotions could reveal important insights about the biological underpinnings of human morality.

“Moral behavior (such as moral emotions, reasoning and judgment) is arguably the most important contributor to stability within and across cultures, although to what extent it is distinct from social behavior per se is unclear,” said study author Keith Kendrick, a professor in the Clinical Hospital of the Chengdu Brain Science Institute at the University of Electronic Science and Technology of China.

“Both moral and social behavior are controlled by overlapping brain regions and individuals with disorders involving social behavior problems, such as autism, borderline personality disorder, psychopathy and obsessive compulsive disorder may also exhibit differences in moral behavior. On the other hand, prosocial and moral behaviors may be dissociable to some extent, involve different neurochemical systems and potentially different therapeutic targets. Our study aimed to address this question.”

To investigate, the researchers recruited 162 healthy adults, aged 18–26, who were randomly assigned to receive either oxytocin, vasopressin, or a placebo via nasal spray. Participants then completed two tasks. The first task assessed moral emotions using scenarios depicting harm to others, asking participants to rate their feelings of guilt, shame, and other emotions when imagining themselves as either the agent or victim of harm. The second task involved moral dilemmas requiring participants to decide whether they would endorse actions that directly harmed one person to save others.

The administration of oxytocin led to increases in feelings of guilt and shame when participants imagined themselves as agents causing deliberate harm. These effects were not observed with vasopressin or the placebo. Additionally, oxytocin reduced participants’ willingness to endorse actions involving direct harm, suggesting a stronger aversion to causing harm compared to the other groups. Importantly, these effects were specific to scenarios involving deliberate harm; oxytocin did not influence reactions to accidental harm.

“The fact that oxytocin only increased feelings of guilt and shame and unwillingness to endorse moral dilemmas in situations involving deliberate, but not accidental, harm to others was unexpectedly specific,” Kendrick told PsyPost.

The study also found that individuals with lower personal distress—an empathy-related trait—showed more pronounced effects from oxytocin. This suggests that oxytocin may primarily enhance moral emotions in people with lower baseline empathy, potentially broadening its therapeutic relevance. Interestingly, neither oxytocin nor vasopressin affected general arousal levels during the moral decision-making tasks, indicating that the observed changes were specific to moral emotions and judgments.

“Overall, the findings in our study support the view that prosocial and moral behaviors are dissociable in terms of the neurochemical systems involved,” Kendrick said. “While the neuropeptides oxytocin and vasopressin can both facilitate prosocial behaviors, only oxytocin could also facilitate moral emotions (feelings of guilt and shame) and making moral judgements, but only in the specific context where other individuals were harmed deliberately. Thus, treatments which can improve prosocial behavior may only influence specific aspects of moral behavior or have no effects at all.”

While the findings are groundbreaking, the study has limitations. The researchers administered only single doses of the neuropeptides, leaving the long-term effects unexplored. Additionally, moral decisions were made in hypothetical scenarios rather than real-life situations, which could limit the applicability of the findings.

“The major limitation in this type of research is that it is only possible to assess moral emotions and decisions in individuals where they are asked to imagine specific scenarios, since clearly it would not be appropriate to observe their behavior under circumstances where they were facing real moral issues,” Kendrick noted.

Despite these limitations, the study highlights oxytocin’s potential in enhancing moral sensitivity and reducing harm-based decision-making, particularly in individuals with empathy deficits. The results open avenues for further research into oxytocin-based treatments for conditions characterized by atypical social and moral behaviors. Future studies could explore its real-world applications.

“The long-term aim of this line of research is to identify molecular targets for therapeutic interventions in individuals with low moral sensitivities and responsibilities leading to immoral actions,” Kendrick said.

The study, “Oxytocin, but not vasopressin, decreases willingness to harm others by promoting moral emotions of guilt and shame,” was authored by Xiaoxiao Zheng, Jiayuan Wang, Xi Yang, Lei Xu, Benjamin Becker, Barbara J. Sahakian, Trevor W. Robbins, and Keith M. Kendrick.