The Disturbing Link Between Sleep Deprivation And False Memories

Sleep deprivation is a serious safety issue and has been implicated in everything from oil spills to plane crashes to nuclear power plant explosions.

It turns out that getting a healthy amount of sleep could also be a justice issue.

A novel study out of University of California, Irvine suggests that sleep deprivation could partly be to blame for false memories -- a phenomenon in which people absorb incorrect information after an event and end up misremembering the incident.

"We already know that sleep deprivation wreaks havoc on your health and cognitive functioning," said lead researcher Steven Frenda, who specializes in human memory at the department of Psychology and Social Behavior at UC Irvine. "It seems another consequence may be that it makes our memories more easily manipulated and more pliable."

"Sometimes memory distortions are trivial and don't matter, but there are contexts (e.g., eyewitnesses in court, clinicians making medical decisions) where errors have serious consequences, so we need to be concerned about factors that make memory less reliable, and more vulnerable to distortion," Frenda continued in an email to The Huffington Post.

Frenda's study, published recently in the journal Psychological Science, is made up of several experiments designed to test participants on their susceptibility to false memories, and compare their results according to how much sleep they had gotten the night before.

In one experiment, researchers asked 193 participants if they had seen video footage of Flight 93 crashing in Pennsylvania on 9/11 -- footage that researchers claimed had been circulated widely, even though no such footage actually exists.

Participants who had gotten five hours or less of sleep the night before ("restricted" sleepers) were more likely than the normal sleepers to claim that they had seen the footage. Fifty-four percent of those with restricted sleep claimed to have seen it, whereas only 33 percent of normal sleepers claimed to remember the non-existent footage.

"One parallel [to this experiment] might be witnesses who are present at the scene of a crime but don't actually see everything," explained Frenda. "They might hear other witnesses talking, or learn more about the event in the aftermath. After learning about things they didn't actually see, they might come to believe they have a more complete memory than they really do."

In another experiment, the same participants were told to keep a sleep diary for a week, reporting on things like length of sleep or the number of times they woke up during the night. After a week was up, the participants reported to the lab, where researchers showed them two sets of photographs depicting a crime in action: one of a man breaking into a parked car and another of a thief stealing a woman's wallet.

After viewing the photographs, participants read narratives that recounted the photo slideshow with several misleading details. Researchers then tested participants to see how many false details from the written narrative they had incorporated into their memory of the photos.

Those who reported sleeping an average of five hours or less every night that week were more likely to incorporate the misinformation into their re-telling of the photo slideshow. The sleep-deprived group did so about 18 percent of the time, while the rested group relayed misinformation 13 percent of the time.

"The misinformation task is meant to parallel a very common situation in the real world: We see an event, later we may encounter suggestive or misleading information, and finally, we are asked to recount the memory," Frenda explained. "The three stages of the misinformation procedure (encoding, misinformation, test) were designed to model this real-world process."

In the last and most compelling experiment, researchers performed the misinformation task on a new group of 104 participants. Participants reported to the sleep lab and were randomly divided two ways: They would either have a full night's rest or stay awake all night. But researchers also randomly split the participants again between those who saw the crime photo slideshow the night they reported to the lab, when they were completely rested, and those who saw the photos the next day, after they either had a full night's sleep or were completely sleep-deprived.

After feeding everyone breakfast the next morning, researchers conducted the misinformation procedure on all the participants. For those who had already seen the photos when they were well-rested, they read the misleading written narrative and then retold the photo stories to researchers. For those who hadn't done any of the procedure, they completed all three parts.

Which group had the highest false memory rate? Those who had stayed awake all night and did all three parts of the photo experiment in the morning. Interestingly, those participants who had "encoded" the slideshow while they were rested had comparable false memory rates, whether or not they eventually went on to sleep or stay awake all night.

"In other words, sleep deprivation seemed most harmful when it was present during all of the processing related to memory -- the 'encoding' of the initial experience, the processing of post-event information, and the recollection of the memory," explained Frenda.

Assistant professor Henry Otgaar, an eyewitness and false memory expert at Maastricht University in the Netherlands, praised Frenda's study for how its experiments approximated real-world situations.

"This study shows that another risk factor for false memory formation is sleep deprivation," wrote Otgaar in an email to HuffPost. "Although this was an expected result, it is troubling -- not only for witnesses, but also for suspects."

Based on research like Frenda's, Otgaar thinks that the legal system should be very interested in how many times suspects or witnesses were interrogated, as well as how much sleep they had gotten before and after the incident. Simple exhaustion, not criminal culpability, could be to blame for someone cracking under the pressure of an intense interrogation, explained Otgaar.

"Consider the following: a suspect is sleep-deprived and interrogated by a police officer," Otgaar hypothesized. "Two days later, he is asked about what they discussed during the first interrogation. It is highly possible that the suspect gives inconsistent answers (because of false memories) and then is seen as unreliable."

But researchers still need to do a lot of work before making any recommendations about changing the process of eyewitness collection and testimony, said Frenda.

"For example, it might be tempting to think that maybe we should send witnesses home to rest before collecting their testimony," said Frenda. "But as more time passes, memories fade and become more vulnerable to distortion. So while you're addressing one risk factor, you might be introducing others."

There's no way to estimate how many people have been wrongfully convicted because of false eyewitness testimony, simply because the total number of wrongful convictions isn't known. But according to the National Registry of Exonerations, a database of every known exoneration in the U.S. since 1989, 36 percent of exonerees were convicted partly because of mistaken eyewitness identifications.

And according to the Innocence Project, an organization that uses DNA evidence to reverse false convictions in the U.S., eyewitness misidentification has contributed to an estimated 72 percent of the 317 convictions that were eventually overturned thanks to DNA.