You have good reason to be leery of someone who has cheated in the past, according to a new study in the Archives of Sexual Behavior.

Researchers surveyed people in long-term relationships about their history of infidelity.

Among people who had been unfaithful in former relationships, 30 percent cheated on their current partners. That’s compared to only 13 percent of those who had never cheated on previous partners.

This pattern holds true for both men and women, and is backed up by previous studies.

The researchers chalk it up to what they call the “threshold effect.”

Once you cheat, committing infidelity again can seem like less big of a deal, says study coauthor Frank Dattilio, Ph.D., a clinical psychologist based in Allentown, Pa.

But that doesn’t mean that cheaters can’t change their ways. Remember, a full 70 percent of those who had strayed in the past were faithful in their current relationships.

So how do you know whether a former cheater is trustworthy?

Talk to your partner about the infidelity—whether it was against you or someone else—and see how he or she reacts, says Dattilio.

If your partner brushes it off and acts like you have no right to be concerned about it, you may have reason to worry, he says. That’s a sign that your partner doesn’t really value faithfulness.

But if your partner comes clean about what happened, acknowledges that it was a terrible mistake, and seems genuinely torn up about it—then you know that he or she takes cheating as seriously as you do, Dattilio says. And you have good reason to trust again.