Researchers asked 152 college students to listen to recordings of both male and female voices counting from one to 10, and rate the likelihood the speaker had cheated in a past or current relationship. All of the people who recorded messages were currently in an exclusive relationship, which ensured they’d had a chance to cheat.
First, participants were asked whether they considered kissing, intimate touching, oral sex, or sexual intercourse to be cheating. Then, they listened to 20 recordings. Half of the recordings featured people who'd never cheated, and half featured people who had cheated at some point. Incredibly, the students were able to identify those who had been unfaithful by rating them more likely to cheat on a scale of one to 10.
"Evidence suggests that many physical, behavioral, and trait qualities can be detected solely from the sound of a person’s voice, irrespective of the semantic information conveyed through speech," says the study's abstract, including, apparently, whether or not they have a wandering eye. Researchers aren't sure why exactly we can tell these qualities from someone's voice, but it sure makes for an interesting thought experiment.