Oxytocin promotes social behavior in infant rhesus monkeys

The hormone oxytocin appears to increase social behaviors in newborn rhesus monkeys, according to a study by researchers at the National Institutes of Health, the University of Parma in Italy, and the University of Massachusetts, Amherst. The findings indicate that oxytocin is a promising candidate for new treatments for developmental disorders affecting social skills and bonding.

Oxytocin, a hormone produced by the pituitary gland, is involved in labor and birth and in the production of breast milk. Studies have shown that oxytocin also plays a role in parental bonding, mating, and in social dynamics. Because of its possible involvement in social encounters, many researchers have suggested that oxytocin might be useful as a treatment for conditions affecting social behaviors, such as autism spectrum disorders. Although oxytocin has been shown to increase certain social behaviors in adults, before the current study it had not been shown to do so in primate infants of any species.

Working with infant rhesus monkeys, the NIH researchers found that oxytocin increased two facial gestures associated with social interactions— one used by the monkeys themselves in certain social situations, the other in imitation of their human caregivers.

“It was important to test whether oxytocin would promote social behaviors in infants in the same respects as it appears to promote social interaction among adults,” said the study’s first author, Elizabeth A. Simpson, Ph.D., postdoctoral fellow of the University of Parma, conducting research in the Comparative Behavioral Genetics Section of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. “Our results indicate that oxytocin is a candidate for further studies on treating developmental disorders of social functioning.”

The study was published online in Proceedings of the National Academy of Sciences.

The researchers began by gauging the ability of rhesus macaques to imitate two facial gestures: lip smacking and tongue protrusion. In lip smacking, the lips are protruded and open, then smacked together repeatedly. The study authors wrote that rhesus mothers will engage in this facial gesture with their infants in the first month after giving birth. Tongue protrusion involves a brief protrusion and retraction of the tongue. Although this gesture is seen in other primates and typically not seen in macaques, macaques will imitate it when their human caregivers display it, the study authors added.

By observing the monkeys’ ability to imitate the two gestures, the researchers sought to determine if oxytocin could promote social interaction through a gesture that was natural to them as well as through a gesture not part of their normal communication sequence.

The researchers tested the infants in the first week after birth. Three times a day, every other day, the caregivers would demonstrate the facial gestures in sequence to the infant monkeys, while the animals’ responses were recorded on video. At this phase of the study, the researchers found that some of the monkeys mimicked their caregivers’ gestures more frequently than did other monkeys. The researchers referred to the monkeys who gestured more frequently as strong imitators.

Beginning in the second week of life, the researchers tested the monkeys on two separate days. The infant monkeys inhaled an aerosolized dose of oxytocin in one session, and a dose of saline in the other. In each session, the dose was delivered through an inhalation mask held gently over the animal’s face.

Overall, the monkeys were more communicative after receiving oxytocin, more frequently making facial gestures, than they were after receiving the saline. The monkeys were more likely to engage in lip smacking than tongue protrusion, but were more likely still to engage in either of these gestures after oxytocin than after the saline. There also were differences in the frequency of gesturing among the individual monkeys, with the strong imitators becoming even stronger imitators after receiving oxytocin.

After oxytocin exposure, the strong imitators were more likely to look at caregivers and stand close to them than they were after the saline. Looking into a caregiver’s face and remaining in close proximity to a caregiver are indicators of social interaction and social interest, Dr. Simpson said.

In another test, the researchers found that after exposure to oxytocin, monkeys had lower levels of cortisol in their saliva. Cortisol is produced by the adrenal glands in response to stress. Lower cortisol levels after oxytocin exposure indicate that oxytocin may also function to diminish anxiety, the researchers wrote.

The material in this press release comes from the originating research organization. Content may be edited for style and length. Have a question? Let us know.


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12 thoughts on “Oxytocin promotes social behavior in infant rhesus monkeys”

  1. Who would have thought that oxytocin can be linked to autism spectrum disorders? I like the fact that scientists are putting so much effort into the study of social behaviors. Monkeys are closely related to the humans, I have faith that the treatment will be successful on humans.

  2. The research done on the effects of exposure to oxytocin in infant rhesus monkeys is surely intriguing. It is amazing to think that a single hormone could have such an effect as to allow stronger social interaction and trust between two different species.

    I strongly agree with the above comment by Ryan Walton, from the given information, that the experiment was carried out in an ethical manner with no permanent effect or harm given to the animals in the experiment. I believe that that is a very important detail which lends credibility to the results of the experiment.

    It is interesting to consider the possibilities that greater exposure to oxytocin in humans can bring about a solution to conditions such as autism spectrum disorder, which may affect an individual’s social behaviour or ability. Especially in our modern society, where being social is such an important aspect, it is good to know that progress is being made in helping people with such disorders be integrated into society more easily.

    Considering that currently, children and infants are breastfed less than they would have been in the past, I think there might be a connection with the growing lack of social skills and social interaction amongst the youth. Natural oxytocin is a hormone that is rather underestimated and undervalued. However, thanks to the above experiment, it may be acquiring a newfound significance.

  3. This blog immediately caught my attention as I had to do an essay based on genetic determinism on ‘morality’ earlier in the year. When I did research for this essay I came across a “TED Talk” presented by Paul Zak in which he mentions one virtue of morality known as trustworthiness and he tests this by recording the amounts of oxytocin in one’s blood after they have fully trusted another being (he achieved this by making people trust others with their money). Results showed that people are more likely to trust another person and interact socially with that person when more oxytocin was present in their blood.

    Evolutionists believe that we use this molecule to increase our social life in order to live in communities and therefore increase our chances of survival. For me, this blog was fascinating and it adds more understanding and proof to the fact that oxytocin is not just a breast feeding hormone.

    I’m not a fan of using animals in experiments but i feel this one was carried out correctly; with exposure to a hormone that won’t have a permanent effect on the monkeys. I still feel, if humans are to use this hormone to correct certain social situations, will it not leave people more vulnerable to crime due to constant trustworthiness? As mentioned in an earlier comment; will an overdose in humans make them more dependent on others? I know that may seem far-fetched but it does cross my mind. In conclusion, I am extremely pleased to see a way forward to help treat or minimize autism spectrum disorders as I know people who suffer from this disorder and to see them interact socially like the rest of us could only bring happiness to that of thousands of parents and families.

  4. The biology of trustworthiness. Oxytocin has often been nicknamed the trustworthy hormone in humans therefore should have the same behavioral effects to other primates. This is information i gathered while doing research on genetic determinism, this article provides a coherent view on this hormone. Studies have proven that the level of oxtocin can change depending on the variety of activities we partake in, for example donating increases levels by 50% and generousity increases by 80%. Neuroeconomists have recently been able to extract another and inject in to another human being. It is a clear indication that oxytocin can help with social disorders.

  5. This experiment with rhesus monkeys is very exciting and insightful. I have also seen similar conclusions deduced in a TED talk by Paul Zak in 2011, where he linked oxytocin levels in the human body with a person’s morality. He concluded that the levels of oxytocin in the body releases different moral feelings, and high levels results in happier people who form better social interactions with other people. This might also explain why oxytocin exposure also causes reduced stress and anxiety levels.

    The success of this experiment with rhesus monkeys now furthers our understanding that oxytocin is definitely linked to social behaviour. The ‘treatment of developmental diseases affecting social skills’ using oxytocin has great potential. Many suffer from autism and other disorders which deny them a normal life, and some even have low levels of oxytocin simply because of their genes. These patients require a safe treatment to ‘boost’ their oxytocin levels and maybe even cure their developmental disorders. However, caution must be taken in administering oxytocin in humans, for abuse of the hormone may create a dependence in humans for it to become socially interactive, or it may even cause new disorders altogether.

  6. What fascinates me the most is that a hormone that is naturally excreted during the birthing process of a mother and the production of breast milk, had an impact on how these monkeys interact with their caregivers. it is suggested that exposure to oxytocin can potentially be the next treatment for autistic human because this hormone increases the social interactions and possibly the physical interest, also increasing the level of communication in monkeys. This interests me because then scientists can seek out natural methods of treating such as autism spectrum disorders caused by high anxiety levels instead of subjecting patients to synthetic treatment measures

  7. Oxytocin, a hormone that is more beneficial then previously known, has many advantages if taken either at an early age, or even as an adult. This article provides us with yet another benefit of the hormone, highlighting its significance in a person’s life.

    The fact that oxytocin improves social interactions and helps people overcome their social inhibitions and fears is an indication of how popular this hormone is going to become, especially in this day and age, where, for example, in a work scenario, shyness and apprehension are considered to be negative attributes.

    These benefits need to be voiced to expecting mothers, as to try and convince them to breast feed rather than use bottled milk. Infants will benefit greatly from the oxytocin they will receive from their mother’s milk, and according to this article, it will decrease the chances of the child being reserved and having social barriers.

    As mentioned at the end of the article, oxytocin is being looked at as a treatment to stress. This is a very important and significant finding, as there are so many harmful drugs that are being used today to try and treat the effects of stress and depression. If this hormone is found to be successful in the treatment of stress, it will undoubtedly become a very popular alternative to detrimental drugs that are on the market today.

  8. This article shows how magnificent science involved in making conclusions as above. I also came across similar results as working in a rehabilitation center we came across these results as when we feed babies with artificial milk without these oxytocin we saw them being less social then the babies we gave artificial oxytocin. This results also backs the data were we can see orphanage babies that grew up on artificial milk is less social and troop orientated than babies that grew up in nature and have been raised on breast feed that contain milk with oxytocin.

  9. These studies are truly magnificent and showing how science has involved to study these facts. I also have come on the same facts as being part of rehabilitation we saw that animals that are given artificial milk without these oxytocin or also know as “trust molecules” are less likely to interact that animals that were given artificial oxytocin with their milk. This article also backs whey most orphanage animals that are not breast feed but given artificial milk are less socials than animals in the nature that gets this oxytocin threw their mothers milk and living more social in the troop or other communities.

  10. This is a very interesting study, seeing as it focuses on a very important aspect of the social interaction between Rhesus monkeys. Oxytocin has a remarkable influence on the behavior of these monkeys, but is also important when it comes to parental bonding and social interactions.
    What is most interesting is the fact that the increase of oxytocin in the monkey’s systems lowered their cortisol levels, making them open to interactions with humans, as well as making them more susceptible to mimicking the facial gestures of their human caregivers.
    As the monkeys were tested during infancy, this helps us determine that oxytocin does have a major effect on the way these animals behave and how they interpret gestures made both by their parents and their human caregivers. I think that this is a very helpful study as it can help us understand and possibly treat social disorders amongst humans. The treatment of social disorders in humans can be a great accomplishment, especially during a child’s developmental years.
    I look forward to reading more about the study and what can be done with this knowledge.

  11. It has also been tested and proven that the bodies of many people are unable to secrete the oxytocin hormone, especially those who had experienced improper nurturing or some form of abuse during their lives. Knowing that rudeness and bluntness can be explained scientifically brings me to realise once again that we ought to be more patient with and understanding of one another.

  12. Oxytocin seems to be a remarkable hormone. Amongst its functions in labour, intimacy and social bonding as the article mentions, it has also previously been referred to as the “trust molecule” and has been said to be involved in one’s sense of morality. The fact that increased levels of oxytocin results in lower levels of cortisol, the stress hormone, leads me to understand that oxytocin has an overall relaxing effect. Once a person is relaxed and calm, that person could be more likely to engage in social interaction, feel more comfortable and allow positive emotions to be evoked. It would be interesting to see what effect oxytocin would have in the treatment of social impairment disorders, such as autism, Asperger syndrome and anxiety disorders.


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