Desiring someone else while in a relationship: what science really says 

You’ve probably already been told that desiring someone else while in a relationship is simply “in men’s nature” at dinner, on a podcast, under a TikTok video. “Men are programmed to look elsewhere, it’s just their nature.” It’s often said with the knowing air of someone who has just explained how the world works.

And it works as an argument. It’s simple, it sounds scientific, and it seems to settle the matter. Except that when you look at what research actually says, the picture is far less clear.

Much more interesting, too.

Let’s take it all apart together.

Where does the idea that men are “programmed” come from?

The argument is based on a real theory, the sexual strategies theory, formulated by psychologists David Buss and David Schmitt in the early 1990s. The reasoning can be summed up in one sentence: throughout evolution, pregnancy cost a woman much more than a man nine months, a risky birth, and years of breastfeeding. Hence the hypothesis that natural selection may have favored greater caution among women when choosing a partner, and greater openness to opportunities among men.

So far, it’s not unreasonable. It’s actually a serious hypothesis that has been debated in scientific journals for thirty years.

The problem isn’t the theory. The problem is what we have turned it into in everyday conversation: we went from a hypothesis about average statistical tendencies to a decree about what “man’s deep nature” supposedly is. Between the two lies a huge gap.

What the data show when you look closely

This is where it gets interesting.

In 2010, two American researchers, Jennifer Petersen and Janet Hyde, compiled data from 834 samples and seven major national surveys to measure gender differences in sexuality. Their conclusion came in two parts.

First: yes, men report slightly more sexual experience and somewhat more permissive attitudes than women across most of the variables measured. The evolutionary hypothesis is not simply dismissed.

Second, and this is the part that rarely gets mentioned: the vast majority of these differences are small. Across thirty behaviors and attitudes studied, none reached the “large” category. Only four were of moderate size: masturbation, pornography consumption, number of partners, and attitudes toward casual sex. And when it comes to attitudes toward extramarital relationships precisely the subject we’re discussing the difference is almost nonexistent.

You read that right. On the question “is it acceptable to look elsewhere?”, men and women give roughly the same answers.

Here’s another, more amusing example. Do you know the “every seven seconds” myth? In 2011, Terri Fisher’s team at Ohio State University gave 283 students a mechanical counter and asked them to click every time they had a sexual thought for one week. The result: around 19 times a day for men and 10 for women. That’s a long way from the 8,000 daily thoughts that the myth would imply.

And here’s the detail that really matters: those same men thought about food 18 times a day and slept 11 times.

In other words, they weren’t thinking specifically about sex. They simply reported more thoughts related to the body across all categories.

Fisher also found something more revealing than gender: the strongest predictor of the number of sexual thoughts was how comfortable people felt with their own sexuality, not their biological sex.

One final methodological point, and it’s worth its weight in gold.

The infidelity figures you see circulating in the French press 46% of men, 38% of women, that kind of thing almost all come from Ifop surveys commissioned by Gleeden, a dating site for extramarital relationships. The research institutes do their work seriously, but a sponsor that sells infidelity has no interest in seeing low numbers. Keep that in mind the next time a statistic lands in front of you.

What we can say, however, is that the gap between the sexes has been narrowing steadily since the 1970s. A biological “programming” that changes over fifty years would be quite an elastic program.

The mini-reflex to develop

The next time you come across a statistic about relationships, ask yourself three questions : who paid for the study, how many people responded, and did people report the information themselves? Thirty seconds of checking, and half the “truths” about relationships collapse on their own.

The experiment that should never have been cited without the follow-up

There’s one study everyone knows without really knowing it. In 1989, Clark and Hatfield sent actors to approach strangers on a campus with a direct proposition. Around 70% of the men accepted. No women. Zero. The figure went around the world and is still used as a knockout argument.

Except that in 2011, psychologist Terri Conley repeated the experiment while changing one variable that nobody had thought to touch : who makes the proposition. She found that women and men spontaneously rated female proposers as more intelligent, more likeable, and better in bed than male proposers when the proposition was exactly the same.

And when she asked female participants to imagine the proposition coming from someone they considered safe, attractive, and probably a good lover, the gender gap disappeared.

In other words: what the 1989 study may have measured wasn’t women’s desire. It was their very reasonable assessment of the risk represented by a stranger approaching them.

Desiring someone isn’t cheating

Now for the part that really matters.

Let’s accept everything above. Let’s even accept that your boyfriend looks, notices, and has thoughts. That’s probably true. It’s also true of you, by the way, even if you’ve been less encouraged to admit it to yourself.

A desire that crosses your mind isn’t an action. It’s not even the beginning of an action. It’s an automatic reaction, like feeling hungry when you walk past a bakery, and nobody has ever claimed that it was biologically impossible to keep walking.

Between desire and action lies exactly what makes us adults: choice. A lie to prepare, a phone to hide, an evening to invent. These aren’t archaic reflexes. They are decisions made one after another, consciously.

And that’s precisely where the “programming” narrative becomes toxic. Not because its premises are entirely false. Because it turns a statistical tendency into a fate, and fate into permission.

An explanation isn’t an excuse

Above all, remember this.

“It’s nature” is one of the most convenient arguments ever invented. It allows someone to tell their partner that what just happened isn’t really their responsibility, but the result of an ancestral force they couldn’t resist.

You can perfectly well accept that desire exists, that it doesn’t disappear simply because you’re in a relationship, and completely reject the idea that it justifies anything. Both can easily coexist.

The real issue in a relationship isn’t whether your partner feels desire for someone else. It’s what the two of you do with those feelings. And that can be discussed. It cannot be dictated in the name of prehistory.

The conversation you really need to have

Not tonight, not in the middle of a tense moment. One quiet day, ask the real question: for both of you, concretely, what counts as cheating? The kiss? The messages? The Instagram account checked three times a day? Research shows that couples often have completely different definitions and that most have never said theirs out loud.

The goal isn’t to create a rulebook. It’s to discover where the other person’s boundaries are before you discover them by crossing them.

What to remember

Desire has no morality, but you do. Biology explains tendencies; it doesn’t sign any authorization. And a man who tells you he can’t help it is mostly telling you that he would rather not have much control over it.

If this subject is stirring something up for you right now, without a doubt, a conversation you can’t seem to have damaged trust it may be worth talking to someone whose profession is helping people through these situations. A couples therapist won’t decide for you; they will simply make the conversation possible.

And sometimes, that’s exactly what’s missing.