Sex Ed

How Many Men Admit To Sexual Assault When Hooked Up To A Lie Detector?

March 16, 2018 by Justin Lehmiller

When comparing the number of women who say they’ve been sexually assaulted to the number of men who admit to perpetrating sexual assault, the numbers are highly discrepant. In fact, the number of self-identified female victims is about three times higher than the number of admitted male perpetrators. So why is that? Is it because a small number of men are committing a large number of sexual assaults? Or is it because men are underreporting their sexually aggressive behaviors? A recent study published in the Journal of Interpersonal Violence offers some support for the latter explanation.

In this study, researchers surveyed 93 men about their participation in a variety of sexually coercive and aggressive behaviors against women. All of the men were aged 18-30, sexually attracted to women, and unmarried at the time of the study.

Participants were randomly assigned to complete the survey under one of two conditions. About half completed it under pretty standard survey testing conditions, whereas the other half completed the survey while hooked up to a device that they were convinced was a lie detector. This involved an elaborate procedure (one that has successfully been used in several past studies) in which participants had electrodes and a heart monitor attached in order to make it seem as legitimate as possible.

Although participants reported believing that the device could indeed detect when they were telling the truth, unbeknownst to them, no physiological data was actually collected when they took the survey. It was really just an elaborate prop designed to encourage honest responding (something social psychologists refer to as the bogus pipeline technique).

It turned out that reports of verbal coercion (e.g., pressuring or manipulating someone else into having sex) were not significantly different across testing conditions. By contrast, reported use of sexual assault tactics was higher among those in the lie detector condition compared to the standard testing condition (37.9% vs. 8.6%). Those in the lie detector condition were 6.5 times more likely to admit to having engaged in a behavior that constitutes illegal sexual assault (e.g., taking advantage of someone who is intoxicated or incapacitated, making threats of physical harm, using physical force).

While these findings are striking, keep in mind that this research relied on a relatively small, non-representative sample of men, which means these findings don’t offer insight into the rate at which men perpetrate sexual assault more broadly. In addition, the researchers collapsed across multiple sexual assault behaviors in their analyses. This is important because when they looked at different types of behaviors separated, reported rates of using physical force were low in both conditions; by contrast, rates of intoxication tactics seemed to differ a lot (this was the primary behavior men seemed more likely to admit in the presence of the lie detector). As a result, it’s important for future research to replicate these results and to give further consideration to different types of sexual assault behaviors.

Limitations aside, these findings are important because they suggest that men may be intentionally underreporting their use of sexual assault tactics on self-report surveys, which could potentially help to explain why there’s such a wide discrepancy between the number of self-identified victims and perpetrators.

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To learn more about this research, see: Strang, E., & Peterson, Z. D. (2016). Use of a bogus pipeline to detect men’s underreporting of sexually aggressive behavior. Journal of Interpersonal Violence

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Written by
Dr. Justin Lehmiller
Founder & Owner of Sex and Psychology

Dr. Justin Lehmiller is a social psychologist and Research Fellow at The Kinsey Institute. He runs the Sex and Psychology blog and podcast and is author of the popular book Tell Me What You Want. Dr. Lehmiller is an award-winning educator, and a prolific researcher who has published more than 50 academic works.

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