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According to a study published on Monday in the Proceedings of the National Academy of Sciences (PNAS), those who are sleep-deprived are 4.5 times as likely as their well-rested counterparts to falsely confess to a crime.

To test the link between sleep deprivation and confession veracity, researchers from Michigan State University asked 88 study participants to complete a number of assignments, including a cognitive test, on computers at the MSU Sleep and Learning Lab over a week. They were repeatedly told not to press the "escape" key in order to avoid losing data. On the night before the experiment ended, the participants slept in the lab. 44 got the recommended eight hours of sleep, and 44 were kept up all night.

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The following morning, each participant was asked to sign a statement summarizing their activities over the course of the test—and falsely accusing them of hitting the escape key.

Half of those who had been up all night signed the document, compared to only 18% of those who had gotten a full night's sleep.

Lead researcher Kimberly Fenn said in a statement that “this is the first direct evidence that sleep deprivation increases the likelihood that a person will falsely confess to wrongdoing that never occurred." She added, “It’s a crucial first step toward understanding the role of sleep deprivation in false confessions and, in turn, raises complex questions about the use of sleep deprivation in the interrogation of innocent and guilty suspects.”

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The study should, indeed, be seen just as a first step. As Ars Technica points out, the stakes of the experiment may simply be too low for it to predict how sleepy innocents would behave when asked to sign a criminal confession. The participants don't face any tangible consequences for lying, and so it's hard to tell why exactly they behaved as they did. From Ars Technica:

People who rated their sleepiness as higher were more likely to sign the statement. That could mean that the more sleep-deprived someone feels, the more impaired their judgment is (as the researchers suggest). Or, it could mean that when someone is super-exhausted, their judgment about the long-term consequences of signing is fine; they just care a lot less about the personal embarrassment of some researcher thinking they deleted some experiment data.

But there's no doubt that false confessions are a real problem for our criminal justice system—according to The Innocence Project, roughly a quarter of people exonerated submitted false confessions. And there's also a lot of evidence that sleep deprivation can seriously impair your judgment, much in the way that alcohol does. Something we should all keep in mind.

Danielle Wiener-Bronner is a news reporter.