Dater Beware

How likely is it that someone who cheated in a past relationship will stray again? Seeking a more precise answer than "likely," psychologists at the University of Denver analyzed the survey responses of young adults over the course of two consecutive relationships. Participants were more than twice as likely to report having sex with someone other than their partner if they had done the same in the previous relationship, the team found. ("Extra-dyadic" sex was used as the best available gauge of infidelity, though for some this category may have included consensual non-monogamy.)

So is discovering a partner's past infidelity a cause for concern? "I don't think it should be a deal breaker," says lead study author Kayla Knopp, but instead "a yellow flag—something to talk through."

Percentage Reporting Sex With Someone Other Than Their Partner

45%...among those who were non-monogamous in their previous relationship

18%...among those who were monogamous in their previous relationship