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Sleep deprivation may lead to false confessions

It may be hard to imagine why an innocent person would confess to a crime they didn't commit, but a number of notorious court cases have shown that it can and does happen.

Now new research suggests that people who are sleep deprived are more likely to sign false confessions than those who are well rested.

The study, published in the Proceedings of the National Academy of Sciences, found that the odds of signing a false confession in a lab experiment were 4.5 times higher for people who had been awake for 24 hours than for those who had slept eight hours the night before.

Researchers from Michigan State University conducted an experiment where they asked 88 participants to complete various computer tasks and a cognitive test during several sessions throughout the course of a week. The subjects were warned several times not to hit the "escape" key on the computer, because "this could cause the computer to lose valuable data."

The study authors note that although whether or not the participants actually pressed the escape key was not monitored, its location on the standard PC keyboard makes it highly unlikely that they would have hit it by accident.

On the last day, half of the participants slept for eight hours in laboratory bedrooms, while the other half stayed awake all night, monitored by research staff.

The next morning, the researchers presented them with a personalized statement describing his or her activities and falsely alleging the participant had pressed the escape key. The subjects were asked to check a box confirming the accuracy of the statement and sign their name.

The results showed that 50 percent of the sleep-deprived group signed the statement with the false confession, while just 18 percent of the rested participants signed it.

Furthermore, the results showed that individuals who had scored higher on an impulsivity test were more likely to falsely confess if they were sleep deprived.

The findings, the study authors say, have important implications for police interrogation practices.

"This is the first direct evidence that sleep deprivation increases the likelihood that a person will falsely confess to wrongdoing that never occurred," Kimberly M. Fenn, associate professor of psychology at Michigan State University, said in a statement. "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."

The researchers note that in the U.S., false confessions are thought to account for 15 to 20 percent of wrongful convictions and previous research has shown that interrogation of unrested, possibly sleep-deprived suspects is commonplace.

Dr. Alan Manevitz, clinical psychiatrist at Lenox Hill Hospital in New York City, said the study was "well-designed" and builds off what we already know about the effects of sleep deprivation.

"We've known for a long time that sleep deprivation has a biological impact on our working memory and cognitive function and reasoning," he told CBS News. "The brain has to work harder in sleep deprived people to compensate for the adverse effects of sleep deprivation. So it makes a lot of sense if memory performance is less efficient with sleep deprivation and the brain has to work extra to make up for it, it could lead to these unfortunate results like false confessions."

The authors acknowledge that the laboratory setting is very different than an actual police interrogation, but Fenn said there is reason to believe the findings could translate to real-world scenarios.

"Our accusation in the study was not coercive at all," she told CBS News, "and in cases like this where you're anonymous and filling out a survey, it's pretty easy to say 'no.' There's a substantial amount of evidence that a lot of times police will often use coercive tactics when they're trying to get someone to confess to a crime. So one can imagine that if sleep deprivation puts you at higher risk of falsely confessing and then you're in a coercive environment, then you're going to be even more likely to falsely confess."

The researchers gave all participants a comprehension test in the morning to make sure they read and understood the statement containing the false allegation.

Another important limitation of the study is that the study authors did not test whether sleep deprivation leads to true confessions, which would potentially make it an effective tactic.

"Of course there are lots of cases where people really do commit crimes and we don't know if sleep deprivation also increases the likelihood that they will confess to crimes that they did commit," Fenn said. "So I don't want to say investigators should not use sleep deprivation because it might help put a guilty person behind bars, but it's a really important question for the scientific community to answer."

However, she did say that a person's physiological state should be taken into account during criminal investigations and police interrogations, and recommended that interrogations be videotaped, giving judges, attorneys and jurors added insight into a suspect's psychological state.

"A false admission of wrongdoing can have disastrous consequences in a legal system already fraught with miscarriages of justice," the authors concluded in the study. "We are hopeful that our study is the first of many to uncover the sleep-related factors that influence processes related to false confession."

Manevitz also noted that while sleep deprivation is an important issue for members of the criminal justice system to consider, the study could offer some insight into how we communicate with one another in day-to-day life.

"There are always a lot of miscommunications and misperceptions in our personal and work lives," he said. "We can't always remember the things we want to remember in the ways we want to remember them. In my practice, it's very common to see couples arguing and each of them swears they remember things a certain way, but with all the sleep deprivation that happens in our society, how can we be so certain in these types of situations?"

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