Reality Check: Does Oxytocin Keep Committed Men Away from Other Women?

The latest oxytocin study says the hormone makes committed men stay faithful, but some skeptics cry foul


Oxytocin, also known as the “love hormone” or the “trust hormone,” frequently makes its way into the news in connection to the latest studies on topics ranging from fidelity to morality to hugs. The most recent addition to the scientific literature, published this week in the Journal of Neuroscience, finds that oxycotin may keep committed men from so much as moving into the vicinity other attractive women.

To arrive at this conclusion, the researchers administered either an oxytocin nasal spray or a placebo to healthy, straight men. Some were in committed relationships; others were not. An hour later, an attractive female assistant entered the room. She altered her distance to each of the men, who were supposed to indicate when she seemed to be at an “ideal distance” or when she stood at a “slightly uncomfortable distance.” Though all of the men, including the ones in relationships, agreed that the attendant was attractive, their comfort levels based upon her physical closeness differed.

i09 details the results:

Interestingly, going into the experiment Hurle­mann’s team predicted that the men, because they had just been administered oxytocin, would be more comfortable as the woman came closer; it is the “trust hormone” after all. But surprisingly, the exact opposite happened. The researchers observed that the men in committed relationships (but not those who were single) kept a greater physical distance between themselves and the woman.

And importantly, committed men who were given the placebo did not insist on the same distance as those administered oxytocin, an indication that the hormone discourages partnered — but not single men — from getting too close to a female stranger.

Before women with husbands and boyfriends rejoice, however, a few notes of caution. Science journalist Ed Yong takes a more pragmatic approach to oxytocin, as he wrote a few months back at Slate:

Oxytocin hype might be storming the heavens, but oxytocin science is still finding its footing. Early studies certainly bathed the hormone in a shiny glow, but later ones uncovered a darker side. The “love hormone” fosters trust and generosity in some situations but envy and bias in others, and it can produce opposite effects in different people. A more nuanced view of oxytocin is coming to light—one that’s inconsistent with the simplistic “moral molecule” moniker.

Researchers’ understanding of the complex physiological and social drivers behind oxytocin’s regulation and effects on individuals remains minimal. And though the science lags behind, Yong writes, hyped coverage of the hormone spurs parents into rushing out to buy oxytocin nasal spray for their children with autism or depression. This creates a potentially dangerous scenario since there have been no studies on the long-term consequences of taking oxytocin. Yong concludes:

In many ways, oxytocin epitomizes what happens when enthusiasm, salesmanship, and optimism runs ahead of evidence and careful experimentation. The true moral of the moral molecule may be that ideas that are too cleanly packaged are probably just fragments.

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