Play ball or go rogue? Oxytocin affects cooperative behavior

Oxytocin, sometimes referred to as the "love hormone," helps to regulate social and sexual interactions. Best known for its role in romantic and mother-infant bonding, scientists are now showing that it could also influence whether we cooperate with others in a team setting.

Researchers Jennifer McClung, Zegni Triki, and colleagues, from the University of Neuchâtel in Switzerland, have wondered about our unique ability to cooperate with other individuals, as well as to withdraw cooperation.

But how, and why, do we sometimes choose to be team players, whereas at other times we prefer to take our chances and go solo?

Many complex factors likely interact to modify our behavior, but the researchers decided to focus on one: our natural oxytocin levels.

Oxytocin is a key hormone and neurotransmitter. In a new study — the findings of which are now published in the journal Proceedings of the Royal Society B — McClung and team looked at how oxytocin can affect our decision about whether or not to cooperate, as well as the conversations we have with people we perceive as "team mates."

"We have for the first time analyzed the natural involvement of this hormone in spontaneous cooperation and conversation between people," McClung says.

A telling game of 'egg hunt'

McClung and her colleagues set up an "egg hunt" experiment, which would allow them to observe when the participants decided to cooperate or withdraw cooperation, and what kinds of conversations they had with each other in circumstances of cooperation.

In the game, paired participants were tasked with hunting for eggs containing either red and blue colored screws. Each player in every pair was offered a reward: one Swiss franc for all the red screws collected, or one Swiss franc for all the blue screws.

Then, the participants were also randomly assigned to one of two groups — "apple" or "orange" — which meant that the members of some pairs ended up in the same group, whereas others would belong to different groups.

This strategy would potentially create a sense of allegiance between participants assigned to the same group.

During the hunt, each player was allowed to choose whether or not to cooperate with their partner and help them find the screws they needed, or whether to go alone and collect only the colored screws they themselves were after.

Oxytocin, cooperation, and affiliation

To assess how oxytocin impacts a person's cooperative behavior, the researchers measured the natural levels of the hormone in samples of each participant's saliva.

The scientists found that people with higher levels of oxytocin were more likely to collaborate spontaneously, but there is a catch: this heightened cooperation was only likelier between people who had been assigned to the same group.

"The same high levels of oxytocin have no effect on two people affiliated to different groups (one 'apple,' the other 'orange' for example)," explains McClung.

"Even if they have a high level of oxytocin, people from different groups hunted alone rather than sharing each other's goals and helping each other," she adds.

But when it came to conversation between partners, the researchers realized that players with high levels of oxytocin spoke less about individual goals with their partners if they belonged to the same group. In these cases, discussion revolved more around the other's goal — including prompts such as "you collect your red screws" — but without offering assistance or joining in with that pursuit.

As for those who belonged to different groups, even if they had higher levels of oxytocin, they still discussed individual goals more.

Taken together, the scientists explain, these results may suggest that oxytocin helps to strengthen social cues so as to support socially appropriate behavior. In other words, it may help to maintain cooperation between individuals with the same affiliation.