Your guy friend’s boasting that he can instantly tell which woman at the bar has straying eyes isn’t entirely hot air, a recent study published in PLOS-One this August suggests.

Recruiting over 100 college-aged men from University of Western Australia to take part in a series of experiments, the authors found that under certain conditions, they could indeed predict the faithfulness of a random woman with better than chance accuracy, using just a brief glance at the women’s photographs.

“Overall, these results show that men’s judgments of faithfulness made from faces of unfamiliar women may contain a kernel of truth,” the authors concluded.

In the first experiment, the authors asked 43 men to rate on a scale from 1 to 7 the faithfulness of 34 female models (aged 20 to 42) after either looking at a photo of their face or their full body — an additional 44 participants were asked simply to rate the models’ trustworthiness and attractiveness. Unbeknownst to the participants, the models had previously divulged whether they had ever engaged in “extra-pair copulations,” with half the women having admitted to at least two such affairs throughout their lifetime, and the other half reporting none.

They then asked these 43 men to simply choose the more faithful of a similarly-aged pair, one having cheated and the other seemingly chaste.

The men’s cuckoldry detector only proved to be slightly effective when comparing the faithfulness of two women presented to them side to side; those who tried to predict the degree of romantic loyalty of an individual women were as successful as someone guessing blindly, validating earlier research. In a second trial of 60 men, the effect was again seen during the multiple-choice portion, to a marginally higher degree of success than in the first experiment.

In both instances, those who looked at the face-only photos appeared to be more accurate than those given a full body photo, and only the men’s assessments of trustworthiness was correlated to the degree of assumed faithfulness — for whatever reason, men didn’t rely on how pretty a woman appeared in order to decide whether she’d remain true to their heart.

Before giving your best bud the go-ahead to help you scope out faithful dates, though, it should be noted that while men were overall more accurate than chance when forced to pick between two women, their accuracy floundered among certain pairs of women. Men who indicated that they especially valued faithfulness in a partner weren’t any more likely to pick out a cheater than those who deemed it less important either.

Still, the researchers did find it “striking that men were able to show any accuracy from images alone after only a brief presentation, considering that accuracy in faithfulness judgments made from behavioral information is relatively poor.”  Though previous studies have found such an effect in women rating men’s chastity via facial images, theirs is the first to show it in men.

Source: Leivers S, Simmons L, Rhodes G. Men’s Sexual Faithfulness Judgments May Contain a Kernel of Truth. PLOS-One. 2015.