Could Oxytocin Change How Our Brains Learn to Help Others?

This post was written by Dr. Daniel Martins, M.D, Ph.D, with edits from Dr. Patricia Lockwood and Dr. Jo Cutler.

As humans, we often make decisions that do not directly benefit us but result in positive outcomes for other people. This voluntary behaviour intended to benefit another person or group of individuals is called prosocial behaviour and holds an important role in social cohesion and well-being. For scientists, understanding why and how we behave prosocially is a mystery that many have been passionately trying to solve.

While the exact reasons behind why we help others, with no clear benefit for ourselves, remain hotly disputed, most agree that to behave prosocially we need to be able to understand and learn the impact our decisions have on others.

Studies have shown that such prosocial learning relies on basic learning processes that are similar to those we use to learn when the outcomes of decisions affect ourselves (self-oriented learning). In general, humans are better at learning about outcomes that benefit themselves as opposed to those that benefit others, although this might change with age. Intriguingly, while prosocial and self-oriented learning share some common underlying brain circuits, prosocial learning engages brain areas that are unique and linked to social behaviour in humans and other primates, such as the subgenual anterior cingulate cortex.

While we have been successful in mapping the algorithms and brain circuits humans use when learning how to behave prosocially, important questions remain. In particular, what molecules in the brain change prosocial learning? Could we potentially intervene chemically to alter how someone learns what actions benefit other people? New research suggests that the hormone oxytocin, commonly referred to as the "cuddle molecule," might be crucial for understanding the parts of our brain involved in learning to help others.

Oxytocin: The Missing Link in the Prosocial Learning Puzzle?

Our research team, led by Dr. Yannis Paloyelis at King’s College London, has studied the human oxytocin system for several years. Oxytocin is a hormone produced in the brain that is well known for its role during labour, breastfeeding, and mother–child bonding. Two decades of research have gathered compelling evidence that oxytocin can regulate social behaviour in many animals, including humans. Moreover, oxytocin is released in the regions of the brain engaged during prosocial learning, such as the subgenual anterior cingulate cortex. Bringing this work together, we wanted to ask: Could oxytocin change prosocial learning? And, if it does, are specific brain areas involved?

To answer this, we designed a new study where we gave three different doses of oxytocin or placebo through the nose (“intranasal” administration) to 24 healthy men on four different days and asked them to perform a learning task while we acquired images of their brains. Participants learned by trial and error which of two symbols was more likely to win them rewards that translated into payments either for the participants themselves (self-oriented) or another person (prosocial) who they met the first time they visited our lab. In each session, people performed this task four times for themselves and another four times for the same other person. Using a combination of advanced statistical methods and brain imaging, we investigated how different doses of oxytocin had an impact on prosocial and self-oriented learning and the underlying brain mechanisms.

A Low Dose of Intranasal Oxytocin Prevented Decreases in Prosocial Behaviour Over Time

We found that as people had to repeatedly perform the task, performance decayed over time when they were playing for the other person. However, a low dose of intranasal oxytocin prevented this decrease in performance; in other words, small amounts of oxytocin led people to maintain high levels of prosocial learning over time. Interestingly, this decreasing performance over time was not observed when participants were playing for themselves. Participants kept high levels of performance over time, which were not affected by oxytocin administration. Our results suggest that a low dose of oxytocin can help people to consistently behave prosocially when needing to learn to help others repeatedly.

Intranasal Oxytocin Affects the Brain Circuits Associated With Prosocial Learning

From previous research, we know learning to benefit others engages specific regions of the brain, such as the subgenual anterior cingulate cortex. Therefore, our next question was this: Does intranasal oxytocin change activity in these specific circuits of the brain during prosocial learning? We found that a low dose of intranasal oxytocin increased the response of the subgenual anterior cingulate cortex during prosocial learning and, importantly, did not affect self-benefitting learning. This was exciting as it shows the effects were specific, and oxytocin was not just changing learning generally.

Previous work using the trust game, an economic game sometimes seen as a measure of prosocial behaviour where people exchange money, has shown inconsistent results of oxytocin. This might be because oxytocin could change our own sensitivity to reward or sensitivity to reward for other people. In our study, we could separate these effects and show a specific effect on learning about other people’s rewards in the subgenual anterior cingulate cortex. Of course, we will need to follow up on these results to show they are replicable in future work.

Implications for Pathological Social Behaviour and New Therapeutic Opportunities

We found that oxytocin is a potential chemical modulator of learning for others, providing the first hints on the neurochemical basis of prosocial learning in humans. Most likely, oxytocin does not operate alone. Other neurochemicals, such as dopamine, that have been extensively implicated in learning might interact with oxytocin to modulate prosocial learning.

Oxytocin Essential Reads

How Oxytocin Affects Our Relationships

The Evolution of the Love Hormone

Another important question is whether disruptions in the oxytocin system contribute to pathological social behaviour by impeding how we learn the positive outcome our actions have for others. If that is the case, then intranasal oxytocin could represent an interesting new therapeutic target for people afflicted by marked antisocial behaviour, such as psychopathy and conduct disorder, some of the least studied and most treatment-resistant psychiatric disorders.