Men given a dose of oxytocin, a hormone known to promote feelings of love and trust, have revealed the chemical’s dark side: It made them more ethnocentric.

When asked to resolve a moral dilemma, such as choosing to save five lives from a runaway train by sacrificing one life, oxytocin-sniffing Dutch men more often saved fellow countrymen over Arabs and Germans than those who didn’t get a hormonal whiff.

“Earlier research of oxytocin paints a very rosy view of it. We thought it was odd a neurological system that survived evolution would make people indiscriminately loving toward others,” said social psychologist Carsten De Dreu of the University of Amsterdam, co-author of a Jan. 10 study in the Proceedings of the National Academy of Sciences. “Under oxytocin we saw an increase of in-group favoritism, which has the downside of discrimination against people who are not part of your group.”

Oxytocin is a hormone made in the brain and some reproductive organs. The body releases the biggest doses of it into the bloodstream during intimate situations (such as caressing), and from there it can dampen fight-or-flight instincts and calm down organs such as the heart.

As a neurotransmitter, it’s also intricately involved in social behaviors such as mother-child bonding, feelings of trust and love, and group recognition.

De Dreu’s "research flies in the face of how we’ve thought about oxytocin for decades. It’s not all about free love and warm fuzzies,” said neuropsychologist Sarina Rodrigues of Oregon State University, who was not involved in the study. “It complements recent data showing oxytocin can promote envy when someone you don’t like wins something, or gloating when you win over someone you don’t like. It’s key to defining where and who we are in society.”

To see how oxytocin influenced behavior, De Dreu and his team rounded up several groups of 60 to 70 Dutch men and sat them in front of computers that led them through one of five experiments. All of the experiments were designed to reveal biases toward or against in-groups, such as fellow Dutch, and out-groups, such as Arabs and Germans (people seen as rivals by many Dutch).

In all of the experiments, men who snorted a dose of oxytocin showed stronger and more frequent favoritism towards their countrymen over rival groups. Men who whiffed a placebo still showed signs of favoritism, but less frequently and at weaker levels.

“In a runaway-train scenario, they were more likely to save men with Dutch names than Ahmeds or Helmuts,” De Dreu said. The men who sniffed oxytocin were also more likely to sacrifice other nationalities, but not at scientifically significant levels.

De Dreu said the work is a starting point, and that he and his colleague would like to do experiments in more true-to-life settings to see how other conditions affect the oxytocin-induced favoritism and subsequent discrimination.

“We’ve shown an increase in ethnocentrism under oxytocin, and we tested this in controlled yet artificial conditions,” he said. “Oxytocin’s effect might be weaker when you’re with your friends walking down the street, but it may be stronger. That’s something we don’t know yet.”

Image: Model of oxytocin./NIH

See Also: