Sleep can help create memories, both real and false, researchers find

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It’s long been known that sleep can aid in the formation of memories. A new study published in the journal Royal Society Open Science suggests that it can help create false memories as well.

Psychologists at Britain’s University of York asked 488 young adult volunteers to study lists of related words, and then to recall those words 12 hours later.

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In the experiment, each subject looked at 20 lists of eight closely related words: for instance, smooth, bumpy, road, tough, sandpaper, jagged, ready and coarse.

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Twelve hours later, they were asked about the lists. But during that time, some of the volunteers were allowed to sleep while others were not. The “sleep” participants studied the words in the evening and were quizzed on them the following morning, while the “wake” group looked at the lists in the morning and were tested the same evening.

Not surprisingly, those who had slept during the 12-hour period scored better on remembering the word lists. But researchers also found that they were more likely to falsely believe that a related word — “rough” in the above example — had been on the list.

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The study also included two control groups who studied the words and took the test immediately afterwards, both in the morning and the evening. Researchers were surprised to find that the time of day the volunteers were questioned about the lists also had an impact on recall accuracy, with more errors and false memories during the evening than in the morning.

They suggested the difference might be due to “interference from sensory/linguistic input accumulated throughout the day.” In other words, 12 hours of activity and chatter might get in the way of remembering all those words.

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As to why the false memories were created at all, the researchers suggest that sleep may benefit “gist abstraction” and “spreading activation.” In other words, the brain is trying to make sense of the information learned as part of a larger pattern rather than individual items.

It’s a useful reminder that our species (and our brains) evolved in the wild, not in a courtroom or laboratory. An interesting test — if I hadn’t just spoiled it by suggesting it — would be to recall what you know about this article after a good sleep. And whether the word “written” appeared other than in this sentence.

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