Joshua Hodge Photography / Getty Images

Is the love hormone the antidote to infidelity? Researchers are doing their best to find out.

Being faithful to a significant other clearly involves a lot more than a hormone. There’s the biology and chemistry that attracts you to your partner, the genes that make it more or less likely that you might take risks in a relationship, your own values about fidelity and marriage, your family’s values about same…you get the picture. But that hasn’t stopped researchers at the University of Bonn in Germany from designing an odd but intriguing experiment to study whether the much-touted “love hormone” oxytocin — the springboard for the bonds between mom and child, lover and beloved — might be enlisted to keep husbands from straying.

Reporting in the Journal of Neuroscience, the scientists, led by Rene Hurlemann of the University of Bonn, invited 57 heterosexual men, about half of whom were in stable monogamous relationships, to randomly receive either six puffs of oxytocin sprayed in the nose, or similar mists of a placebo compound. In the first part of the experiment, each of the male participants stood with his toes on a line while an attractive female researcher whom he had never met before walked towards him. When the female scientist reached what each participant felt was an “ideal” social distance in terms of the physical space between them, he was instructed to say ‘stop.’

In the second half of the experiment, the positions were reversed and the female researcher stood on the line while each of the men approached her and stopped when he reached what he considered the appropriate social distance.

The men in the monogamous relationships who were given oxytocin recorded the greatest distances between them and the attractive female — between 28 inches and 30 inches compared to 20 inches to 24 inches recorded for the single men and those receiving the placebo spray. (The men in relationships were more likely to call for an early stop to the researcher’s advances if she looked them in the eye.) The effect was the same when the female researcher was replaced with photos of attractive women: men in relationships were slower to bring the pictures toward them on a computer.

When the experiment was repeated with a different group of heterosexual men and a male researcher instead of a pretty woman, however, oxytocin did not seem to have much effect; both the oxytocin and placebo groups asked the male scientist to stop at about the same distance.

“This is the first study to suggest that oxytocin may play a role in maintaining monogamy in humans by causing men in a monogamous relationship to keep a distance from attractive women,” Larry Young, professor of psychiatry at Emory University said in an email discussing the results. Young studies the effects of oxytocin but was not associated with the study.

MORE: A Blood Test to Predict Everlasting Love?

Previous research has shown that oxytocin levels increase and remain high in the early days of romantic love— and that levels rise further not only after sex, but also if the members of a couple simply are in close proximity to one another. The study’s authors write that oxytocin’s ability to promote monogamy in men “may normally depend on the presence of a close positive relationship in the bond with their female partners and close physical proximity between the couple.”

Indeed, the study found that attached and single men given placebo, and therefore not under the influence of oxytocin, were equally likely to stand close to the attractive researcher, suggesting that monogamy itself doesn’t always elevate oxytocin levels sufficiently to promote fidelity. It takes monogamy and continued close contact with a partner to maintain those hormone levels, especially after the first bloom of love has faded. “These findings suggest that women could increase the faithfulness of their partners by engaging in behaviors that stimulate his oxytocin release, including intimate relations,” says Young.

The research also adds to the evidence that oxytocin doesn’t simply make people feel close to whomever happens to be nearby. “Oxytocin is not just a “cuddle” hormone that always promotes social interactions as the popular press often portrays it,” Young says, “Context is critical. In this case it actually promotes social distance.” Which sometimes can be a good thing.

MORE: Q&A: Neuroscientist Larry Young on Sex, Drugs & Love Among Voles