Administering the hormone oxytocin to infant rhesus macaques appears to increase social behaviors in these newborn primates. These results may suggest that oxytocin could be used as an early therapeutic tool to improve social behaviors in individuals at risk of developing certain neurodevelopmental disorders.  The study has been published in the journal PNAS.

Oxytocin, sometimes nicknamed the “love hormone” or “cuddle hormone”, has been found to have a wide range of effects on social behaviour. Studies have shown that the administration of oxytocin can enhance social behaviors and social attention in both humans and non-human primates. It is because of this that some scientists believe that oxytocin could potentially be used as a form of treatment to promote social affiliation in individuals with disorders that affect social behaviors.

Previous studies, however, have focused on its effects in adults and have neglected to investigate whether exogenous (administered) oxytocin can affect social behavior in infants, which is where this study fills in gaps.

In this particular study researchers wanted to investigate whether oxytocin, in comparison with a saline control, promoted behaviors in newborn macaques that are associated with social interactions. They focussed on the ability of these animals to imitate two facial gestures; lip smacking and tongue protrusion. Lip smacking is often used by these monkeys in certain social situations and mothers will demonstrate this gesture to infants frequently within their first month of life. Tongue protrusion on the other hand is not commonly seen in macaques, but they imitate humans that demonstrate it.

During the week following their birth, human caregivers demonstrated the gestures to the infants regularly and recorded their imitative ability. The researchers found that some infants imitated the gestures to a greater extent than others, which were designated strong imitators.

In week two, the researchers administered aerosolized oxytocin or saline to the infants on two consecutive days, where one treatment was given per day. Two hours after administration the researchers carried out imitation recognition tasks on the macaques. They found that the monkeys produced more facial gestures after receiving oxytocin than when they received saline.

They also found that the previously designated strong imitators increased the frequency of gestures after oxytocin exposure to a greater extent than the others that were not in this category. Furthermore, these strong imitators were more likely to display behaviors that are indicative of social interaction, such as staying close to the humans, when they were given oxytocin rather than saline.

The researchers also collected and analyzed saliva samples from the infants. Not only did the administered oxytocin increase salivary oxytocin levels only two hours after exposure, it also decreased levels of cortisol in the saliva, which is known as the “stress hormone”, although it did not decrease stress-related behaviors. This could suggest that administration of oxytocin may reduce anxiety. They also found that those with higher levels of salivary oxytocin displayed greater social interest.

Taken together, these results suggest that the administration of oxytocin to infants can positively affect the social behavior of these primates, and may hint that oxytocin could be used as an early intervention for those at risk of developing disorders that affect social function.