Psychologists Find Sleep Can Distort Our Memories

While having a good night’s sleep might help you to remember things you’re trying to remember, it can also help our brains make up entirely false memories.

The human brain’s memory is notoriously unreliable, often missing things that were glaringly obvious or remembering things happening that never actually did. New research in the journal Royal Society Open Science reveals that sleep might help us remember things, and also remember false memories.

These false memories often arise when people are given a list of related words to memorize, and falsely remember a word being there that would have fit the category but in fact was missing.

“We found that participants had better memory for the lists in terms of better recall of the words in the lists. But their errors were also revealing—they made fewer random errors (intrusions), and more errors that suggest that they had learned the gist of the lists,” Gareth Gaskell, a professor of sleep psychology at the University of York in England, told Newsweek.

The researchers tested 488 participants on their ability to recall a list of words 12 hours after seeing them, with some of the participants being allowed to sleep in the 12-hour interim.

They found that those who had slept remembered more of the words on the list than those who had not, but they were also more likely to give words that weren’t on the list, but were related. The related incorrect words are known as “lure words,” while completely unrelated incorrect words are known as “intrusions.” If a list contained words like nurse, hospital and sick, the false memories may include lure words like doctor.

“The results suggest an intriguing combination of effects. The sleep and wake groups were well-matched in the number of total responses after the 12-hour delay. Despite this, the sleep participants were more accurate in their veridical (truthful) memory of the studied list words, as well as more gist-like in their incorrect responses—a greater lure-to-intrusion ratio,” the authors wrote in the paper.

This suggests that sleep has a complex role in memory, influencing not only how well memories are retained but also potentially the nature of the memory.

“Memories in some ways are more about our future than our past. What we want is knowledge about our past that can be applied in a generalized way to help us to deal with future events,” Gaskell said.

“Future events won’t be identical to the past events, so a gist-like representation might actually be more useful than a ‘perfect’ detailed representation. So what sleep might be doing is helping us to store memories in a gist-like way that can then be better applied to our future interactions.”

The researchers also found that the results varied based on the time of day that the participants were remembering the list, with both groups suggesting more incorrect and unrelated words in the evening.

“We found an unexpected time-of-day effect, such that completing free recall in the evening led to more intrusions—neither studied nor lure words,” the authors describe in the paper.

“Above and beyond this time-of-day effect, the sleep participants produced fewer intrusions than their wake counterparts. When this was statistically controlled for, the sleep participants falsely produced more critical lures. They also correctly recalled more studied words, regardless of intrusions.”

The authors do recognize several limitations of their study, namely that all participants were aged between 18 and 25, and that the tests were performed online, meaning that other distractions and environments could not be controlled.

However, they hope that their research paves the way to new discoveries regarding sleep’s role in memory.

“Our study provides a rich new body of evidence to help determine the contribution of sleep,” they wrote.

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