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Spotting Cheaters: How Long Do You Have to Know a Person Before You Can Do It Accurately?

Most people who are cheating on their romantic partners don’t want to be caught. They don’t want their partners to recognize their infidelity, and they don’t want other people to be able to tell, either.

So is it possible for people to just watch a couple and know whether one of the partners is cheating on the other? If so, how long would you have to know the possible cheater? Would you need to be a close friend or maybe a relative who has known the person their whole life? Would you need to be the person who is getting cheated on?

The romantic partner who is getting betrayed by their partner may well be the last to know. Often, they just really do not want to know – they are motivated to believe that their partner would never do that to them. Careful research shows that romantic partners are sometimes worse than complete strangers at knowing when their partner is lying.

In a recent set of studies, psychologists made the brazen prediction that total strangers could recognize, at a level that is better than chance, whether someone is cheating on their romantic partner, and that they could figure that out by watching the couple interact for only about four minutes!

In each of the two studies, college student couples interacted with each other for about 3-5 minutes. Their interactions were videotaped. One person in each couple completed a measure assessing any physical or emotional infidelity to their partner. (Of course, their answers were for the researchers’ eyes only.) The videotapes of the interactions were shown to complete strangers, who were asked to focus on the key person (the one who reported on his or her own infidelity). Those strangers reported their impressions of whether that person was cheating on their partner, by answering questions such as “How likely do you think this person has had sexual intercourse with someone other than his/her partner?” In the second study, the strangers also indicated their impressions of how committed to their romantic partner the person seems to be, and how trustworthy the person seems.

Based on only about 4 minutes of observing the couples, the strangers could tell, to a moderately successful degree, who was cheating and who was not. Their impressions correlated significantly with the key persons’ own reports of their cheating. The strangers seemed to use their sense of the person’s trustworthiness and commitment to their partner as clues to whether they were cheating.

The couples in the study and the strangers who observed them were all college students, and the strangers were almost all women, so as social scientists like to say, “More research is needed.” It is interesting, though, that people can get a pretty good sense of who is a committed romantic partner and who is a cheater from such a “thin slice” of their behavior.

Reference: Lambert, N. M., Mulder, S., & Fincham, F. (2014). Thin slices of infidelity: Determining whether observers can pick out cheaters from a video clip of their interaction and what tips them off. Personal Relationships, 21, 612-619.

Spotting Cheaters: How Long Do You Have to Know a Person Before You Can Do It Accurately?

Bella DePaulo, Ph.D

Bella DePaulo (Ph.D., Harvard; Academic Affiliate, Psychological and Brain Sciences, UC Santa Barbara), an expert on single life, is the author of several books, including "Singled Out: How Singles Are Stereotyped, Stigmatized, and Ignored, and Still Live Happily Ever After" and "How We Live Now: Redefining Home and Family in the 21st Century." Her TEDx talk is "What no one ever told you about people who are single," Dr. DePaulo has discussed singles and single life on radio and television, including NPR and CNN, and her work has been described in newspapers such as the New York Times, the Washington Post, the Wall Street Journal, and USA Today, and magazines such as Time, Atlantic, the Week, More, the Nation, Business Week, AARP Magazine, and Newsweek. Dr. DePaulo is in her sixties. She has always been single and always will be. She is "single at heart" -- single is how she lives her best and most meaningful life. Visit her website at

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APA Reference
DePaulo, B. (2014). Spotting Cheaters: How Long Do You Have to Know a Person Before You Can Do It Accurately?. Psych Central. Retrieved on February 20, 2020, from


Last updated: 28 Dec 2014
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