Yes, there’s a way to predict infidelity. No, it’s not by how much sex you’re not having.

Yes, yes, Valentine’s Day is a day of love. But let’s be real: Our options for love have never been so many — nor our opportunities for cheating.

“With the advent of social media, and thus the increased availability of and access to alternative partners, understanding how people avoid the temptation posed by alternative partners may be more relevant than ever to understanding relationships,” said psychologist Jim McNulty. McNulty is the lead author of a new study, published in the Journal of Personality and Social Psychology, looking into the factors that help a couple avoid infidelity (one of the surest ways to cause a breakup) and stay in a long-term relationship.

For three and a half years after marriage, McNulty’s team followed 233 couples, documenting intimate details about their relationships, including marital satisfaction, long-term commitment, whether they had engaged in infidelity and if they were still together.

The team identified two psychological abilities linked to faithfulness: attentional disengagement, or the ability to direct your attention away from an attractive person who could be considered a romantic option (internal monologue: “Super hot — oh, look, something more interesting”), and devaluation of potential romantic partners, or, the tendency to mentally downgrade the attractiveness of another person, even if they’re extremely good looking (internal monologue: “Very, very attractive … if you like birds.”).

Read more: Online Cheating Is the New Elephant in the Room

The team tested newlyweds on those processes by showing them photographs of highly attractive men and women, as well as average-looking men and women. Participants who quickly disengaged their attention from an attractive person were less likely to cheat. The split seconds told the story: Individuals who looked away in as little as a few hundred milliseconds faster than average were nearly 50% less likely to have sex outside marriage.

The tendency to devalue, or downgrade, the attractiveness of potential romantic partners also lowered the risk of infidelity and raised the likelihood of maintaining the relationship. Faithful people evaluated romantic alternatives much more negatively.

On the flip side, individuals who looked at romantic alternatives longer had a higher risk of an affair after marriage, and their marriages were more likely to fail.

Unfortunately, “people are not necessarily aware of what they’re doing or why they’re doing it,” McNulty said. “These processes are largely spontaneous and effortless, and they may be somewhat shaped by biology and/or early childhood experiences.”

However, that doesn’t mean some people are doomed to cheat. McNulty said while these mental reactions may be ingrained to some degree, a growing body of research suggests scope for individual improvement in disengaging or devaluing when tempted.

Yet, how we react internally to attraction is not the only predictor of whether people cheat. Perhaps surprisingly, the research team found people satisfied with sex in their relationship were more likely to be cheat, perhaps, the team suggested, because they felt more positive about sex in general and would seek it out regardless of how they felt about their main relationship. Youth and less overall relationship satisfaction also predicted cheating on a partner.

Read more: Marital Infidelity: Why It Happens

And in a final bombshell, a person’s history of sex was a predictor of infidelity, too — but not in the way society would have us believe. Men who reported having more short-term sexual partners prior to marriage were more likely to have an affair — but women who had more short-term sexual partners before marrying tended to be more faithful. (Can this finally lay to rest the wild oat sowing and virgin bride double standard?)

These findings are, perhaps, more useful for monitoring ourselves than policing partners. Machines can parse split-second glances, but human eyes cannot. And as much as we’d like to think we know our partners’ inmost thoughts on attraction — or at least their outward expression of it — we probably don’t, not in every instance. (And really, who would want to?) McNulty and co.’s findings, while interesting, hint that perhaps at the end of the day, the biggest predictor of fidelity is an X factor science can’t measure: trust — both earned and given.