If you have ever had trouble sleeping, you probably know what it feels like to function on less than adequate sleep.  Reaction time slows down, cognitive abilities are clouded and you can't seem to remember anything. Indeed, studies have long shown that poor sleep inhibits memory.  But a new study took a look at how sleep affects a person's risk of forming false memories - recalling events that never actually happened - and found that sleep deprivation greatly increases the likelihood of this occurring.

For the study, researchers from the University of California, Irvine and Michigan State University performed three different experiments in an effort to test out real-life situations in which a person might have poor sleep and be asked to recall a specific event.  Researchers were particularly interested in scenarios that mimicked the witnessing of a crime and how poor sleep might affect a person's chances of recalling the event incorrectly.  

In the first phase of the study, lead researcher Steven J. Frenda of the Department of Psychology and Social Behavior at UCI and his team asked 193 participants if they had seen video footage of Flight 93 crashing in Pennsylvania on 9/11.  Researchers told the participants that this footage had been circulated widely, even though no such footage actually exists.  Participants who had been restricted to five hours of sleep or less the night before were more likely than those who had a regular night's sleep to claim they had seen the footage.

For the second study, the same participants were asked to keep a sleep diary for one week.  At the end of the week, researchers showed the participants images of a crime in action - one of a man breaking into a parked car and another of a thief stealing a woman's wallet.  They were then asked to read accounts of the incidents that included several misleading details.  Again, the participants who recorded the least amount of sleep over the week were the most likely to incorporate the false details of the incidents into their memories of the photos.  

In the final phase of the experiment, researchers randomly divided a group of 104 new participants at the lab into those who would be allowed to have a normal night's sleep and those who would not be allowed to sleep at all.  Then they divided these two groups again into those who would be shown images from a crime the night they reported to the lab (well-rested) and those who were shown the images the next morning (after either a full night's rest or no sleep at all.)  In the morning, the researchers conducted a misinformation experiment similar to that performed in phase two.

Not surprisingly, the participants who conducted all parts of this experiment while sleep deprived were the most likely to incorporate false details into their memories of the events.  What is surprising is how closely this experiment simulates an actual interrogation of a person who has witnessed a crime and how easy it is for these witnesses - on less than adequate sleep - to incorrectly recall what happened, or to believe that they saw something or someone that they didn't.

Related posts on MNN:

Does sleep deprivation lead to false memories?
New study questions the reliability of crime scene testimony from sleep-deprived witnesses.