Hormone Helps Keep Married Men Away From Unknown Attractive Woman
November 14, 2012

Hormone Helps Keep Married Men Away From Unknown Attractive Woman

Lawrence LeBlond for redOrbit.com - Your Universe Online

It´s only natural that married men continue to check out other attractive women that happen to come into their field of view. Occasionally, some of these men also have a tendency to seek out these women and make contact. And some may even pursue these women further.

But now, a new study published in Tuesday´s issue of the Journal of Neuroscience has uncovered a surprising new property of a hormone they say will keep married men from straying too far from their wives. In fact, when monogamous men involved in the study took a little sniff of the hormone, called oxytocin, they were less inclined to interact with an attractive woman they had just met.

The findings of the study suggest oxytocin may help promote fidelity within monogamous relationships.

Researchers had already known that oxytocin plays an important role in triggering childbirth and facilitating nursing, and previous studies have even shown a link between the hormone and increasing trust among individuals. However, scientists had yet to determine what role oxytocin played in maintaining monogamous human relationships.

Oxytocin is produced in a region of the brain called the hypothalamus, and is known for forming social bonds. In humans and other animals, this brain hormone is known to promote strong social bonds between parents and their children, and also between couples. So it only makes sense that researchers have found the hormone may help keep couples monogamous.

In the study, led by Rene Hurlemann, MD, PhD, University of Bonn, researchers found that men in committed relationships who were given oxytocin kept a greater distance when approaching or being approached by an unknown woman they found attractive compared with those given a placebo. The researchers noted that the hormone, however, had no effect on single men.

The researchers found that single heterosexual men had no trouble being within 24 inches of attractive female strangers. But for monogamous men who were given a healthy dose of the hormone, they stood, on average, about 6.5 inches farther away from the comely females.

Even more impressive was that when monogamous men were only shown a photograph of an attractive female, those who were on the oxytocin also kept a bit more distance between them and the picture. However, when the new acquaintance was another man, the oxytocin had no different effect on attached men than as with single men, noted the researchers.

Previous research on female prairie voles has suggested the chemical might play a role in pair-bonding, and in humans playing games of risk and power, the hormone increased empathy and trust in males and females alike. When researchers further examined the effects of oxytocin on people, they, along with those involved in the new study, assumed that men would be drawn closer to women, not farther away.

"This was quite surprising," Hurlemann noted, adding that it does, however, make evolutionary sense.

“As human societies evolved to give men an increasing role in safeguarding and supporting their mates and offspring, it appears that oxytocin may have taken on a more discriminating role in human interaction by favoring staying over straying behavior among men who've already found a mate,” wrote Los Angeles Times´ Melissa Healey, citing Hurlemann.

For the study, Hurlemann and his colleagues administered oxytocin or a placebo via a nasal spray to a group of healthy, heterosexual males. Forty-five minutes later, the men were introduced to a female experimenter that they later described as “attractive.” As the experimenter moved toward or away from the study group, the men were asked to indicate when the experimenter was at an ℠ideal distance´ and also when the experimenter was a distance that made the men feel “slightly uncomfortable.”

“Because oxytocin is known to increase trust in people, we expected men under the influence of the hormone to allow the female experimenter to come even closer, but the direct opposite happened,” Hurle­mann said.

The effect of oxytocin on the monogamous men was the same regardless of whether the female experimenter maintained eye contact or not, or if the men were the ones approaching or withdrawing from the experimenter.

“In monogamous prairie voles, we know that oxytocin plays an important role in the formation of the pair bond,” said Larry Young, PhD, an expert on oxytocin at Emory University who was not involved in the study. “This study suggests that the general role of oxytocin in promoting monogamous behavior is conserved from rodents to man.”

Paul Zak, founding director of Claremont Graduate University's Center for Neuroeconomics Studies, said the findings suggest oxytocin isn´t merely making people friendlier–it´s making them more empathetic, more attuned to social cues, and more inclined to adjust their behavior accordingly.

However, the study also suggests something important about the ways in which the human brain differs from those of other animals, noted Zak, who was not involved in the new study.

“The finding that one's relationship status affects how oxytocin affects the brain provides some evidence that our brains evolved to form long-term romantic relationships,” he told the LA Times.

Hurlemann´s study was funded by the Ministry of Innovation, Science, Research & Technology of the German State of North Rhine-Westphalia (MIWFT) and the University of Bonn.