Oxytocin: the Good and the Bad

Oxytocin is made in a part of the brain called the hypothalamus, but it influences the entire body. It spikes when we’re sexually aroused, makes wombs contract before birth, and triggers the release of breast milk. For decades, animal studies have shown that oxytocin is important for social interactions. If you block the hormone, monogamous voles become more promiscuous and ewes neglect their newborn lambs.

Then, in 2005, Michael Kosfeld and Markus Heinrichs asked volunteers to play a game of trust after sniffing either oxytocin or a placebo. (Zak, often solely credited for this work, was the third author on the paper.) The volunteers had to decide how much money to invest in an anonymous partner, who could reimburse them later or keep all the money. Despite the potential for betrayal, the oxytocin-sniffers entrusted more money to their partners than those who sniffed a placebo.

[...] Various research groups showed that oxytocin sniffs can make people more trusting, generous, cooperative, sensitive to the emotions of others, constructive in their communications, and charitable in their judgments of others. Zak continued to link oxytocin with trust and generosity, although John Conlisk, an economist from the University of California at San Diego, later analyzed those papers and suggested that “some conclusions are too enthusiastic.”

[...] Some scientists have found that oxytocin boosts envy and schadenfreude, as well as favoritism toward one’s own clique. In one experiment, volunteers who played a game with people they knew were more cooperative after a noseful of oxytocin, while those who played with anonymous strangers became less cooperative.

Jennifer Bartz, from the Mount Sinai School of Medicine, has found several responses that depend on a person’s mindset. She showed that socially secure people remember their mothers in a more positive light after inhaling oxytocin, while anxious ones remember mum as less caring and more distant. Along similar lines, she showed that oxytocin hinders trust and cooperation among people with borderline personality disorder.

These nuances didn’t come out of the blue. When Bartz looked at the early oxytocin studies more closely, she found that around half of them showed that the hormone enhanced positive behavior only in certain situations or individuals.

Sue Carter, who did much of the early oxytocin research with animals, views oxytocin as part of an adaptive system that allows us to coordinate our behavior with our social situation. It's a system that acts against the background of our histories and emotions.


[Bartz] already have some good ideas [on what oxytocin does]. Maybe oxytocin is a motivator that drives us to seek out social interactions. That would explain why it improves trust in some situations but drives bias and favoritism in others. More likely still, oxytocin could be a spotlight that draws our attention to social cues, making them more noteworthy. If we are naturally sociable, that’s a boon. If we are anxious, oxytocin only exacerbates the things that make us nervous.

[...] The truth [about oxytocin], as they say, is a bit more complicated than that.

-- Ed Yong

from "One Molecule for Love, Morality, and Prosperity?: Why the hype about oxytocin is dumb and dangerous."

Quoted on Thu Jul 19th, 2012