We cross paths with all sorts of people in our lives – lots of them good looking enough to set our pulses racing. But if we’re in a committed relationship, most of us don’t flirt with the cute guy or girl who sits next to us in class, nor do we slip them our phone number. Instead, we make the choice to stay faithful to our partners.

So what’s the secret to staying faithful? It turns out there’s something that committed couples do to  make it easier. And they don’t even realise they’re doing it. Curious what it is? So were a group of US researchers.

Sexy strangers 

In fact, they already had a pretty good hunch. Past research had shown that when people in relationships meet a hot, witty, intelligent stranger, they say they’re not too impressed.

“Good looking? Mmm so-so,” they’ll say. “Funny guy? Well, he didn’t make me laugh.”

Are they just being tactful? Are they consciously talking themselves out of falling for a sexy stranger? Or does it actually happen without them really being aware of it?

The researchers set up a test with a couple of hundred students, some single, some in relationships. The students were told they were going to be working closely with a member of the opposite sex. They were shown pictures of this guy or girl – who just so happened to be really hot! They also read profiles that revealed whether the person was single and interested in dating, or already taken.

Later on, the students were shown 11 different photos of the guy or girl. One  was the photo they’d already seen, the rest had been cunningly photoshopped. In half of them the person had been morphed to make them less attractive, and in the rest they’d been made to look even more attractive. The students had to pick out the real deal.

Cooling down hot impulses 

Would the students in relationships choose differently from those who were single?

Sure enough, the students in relationships picked out a photo that made the person look less attractive than they really were. These faithful lovers really did remember the hot stranger as “Good looking? Mmmm so-so.” Especially if they were told the person was single and looking for a hot date – so even riskier as a tempting illicit lover.

Things were different if the students were told the person was already tied up in a relationship or not interested in romance. It was safer to admit they were sexy without being led astray. Then the students actually picked out a photo that made the guy or girl look even more attractive than they were in reality.

So when someone is in a loving long-term relationship, one of the ways they stay faithful seems to be to downplay the attractiveness of a guy or girl who’s a threat to what they’ve got going with their partner, the study showed. And this isn’t a question of choosing to think he or she is less attractive. The results suggest people in happy relationships actually see good-looking guys and girls this way. As the researchers put it, happy couples cool down their hot impulses when they see an attractive stranger.

This article was originally published on our sister site Love Matters