We've all heard of the reasons people in relationships cheat. But new research from Rutgers and New York University explains how and why couples stay faithful.

Starting out with the observation that a lot of relationships are successful, the goal of the study was to find out strategies or factors that might influence whether people are likely to stay true, according to Shana Cole, assistant professor of psychology in Rutgers' School of Arts and Sciences, the lead author of the study.

"The main reason we found is that people have a nonconscious, implicit, protective perceptual bias," Cole said.

"One thing that might help people who are in committed relationships stay with their current partners, is this bias they might have to see other attractive people — particularly those who might represent a threat to their own relationships — as less attractive."

In other words — the guy or gal at the end of the bar might be awfully attractive, but if you're in a committed relationship, you may be less likely to think so.

The research is based on a couple of studies designed to look at that concept using mostly undergraduate students in universities, according to Cole. Students were given certain scenarios in which they think attractive people are interested in them or flirting with them, or romantically available.

"Then we ask them questions about how attractive they think the other person is," Cole said.

The researchers used a technique known as a "visual matching measure" — meant to get at "their real perceptions of attractiveness, and not just what they think about this person, but how they actually see them."

The result? People deemed attractive by single participants were often deemed less so by those paired up.

Cole noted the specific sample of younger students represent people who may not have been in relationships for very long and also have lots of options available to them at this stage in their lives.

There's plenty out there on why people cheat, but "we kind of want to speak up for the other side to say they're are protective relationship strategies, or biases, that people have that help them to stay faithful," Cole said.

She also said researchers are interested in next finding out whether longtime, married couples have the same strategies or different ones to stay faithful, as well as, "what other strategies do people have that might help them to meet any goals that they might have in relationships, or in dieting or in exercise, so that's an exciting area of research for us."

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