Scientists, and women everywhere, have always asked: what keeps a man get married and stick around to raise their kids?

Researchers think they may have found a clue in oxytocin, a hormone released during sex and other intimate gestures like hugging or holding hands that's been proven to strengthen social bonds in other mammals, Newsmax Health reports. The hormone appears to boost men's attraction to their mate -- even when presented with pictures of other women.

In the study, 20 men who were in committed relationships for 28 months, on average, took whiffs of either oxytocin nasal spray or an inactive placebo spray.

For the first test, the men looked at pictures of their partner, a woman they'd never met, or a house. The photos of the women were carefully matched so one wasn't more attractive than the other.

In the second experiment, they looked at pictures of their partners or of women they knew but weren't related to, perhaps someone they saw at work every day.

Then the men rated the attraction they felt to the various faces. Men consistently rated their partners as being more attractive and arousing than the other women and, in most cases, a whiff of oxytocin boosted that effect compared to the placebo.

 But what really fascinated the researchers was what happened inside the men's brains.

Under the influence of oxytocin, two areas of the brain responsible for feelings of reward and pleasure lit up when men saw their partner's faces. But the sight of other women had the opposite effect, suppressing feelings of pleasure.

Larry Young, a professor of psychiatry at Emory University in Atlanta said the results suggest that couples who keep a high level of intimacy in their relationships can maintain stronger bonds.

As time goes on, and couples become less intimate, linkage can decay. But activities that release oxytocin, such as really looking into another person's eyes, holding hands, kissing and having sex may help restore the connection.