Secret Sleep Memory

Our memories for certain types of info seem to improve more during sleep than during wakefulness, a new study reports.

A neuroscience researcher, hard at work on a complex problem.

Researchers have found that recall for pairs of words improves dramatically after a period of sleep, as does working memory capacity. An equivalent period of wakefulness results in much less improvement in these areas than sleep does, suggesting that a distinct type of memory consolidation may be happening during sleep.

Neuroscientists have known for years that sleep can help us learn. Watching or reading information right before you doze off can dramatically improve recall. Even physical skills, like playing an instrument or a sport, seem to improve more rapidly if a person practices right before bed.

What this new research seems to imply, though, is that “sleeping on a question” not only improves our understanding of that particular question, but on future questions of the same kind:

Memory for word pairs reliably improved after a period of sleep, whereas performance did not improve after an equal interval of wakefulness. More important, there was a significant, positive correlation between WMC [working memory capacity] and increase in memory performance after sleep but not after a period of wakefulness.

In other words, volunteers’ working memory, as well as recall for word pairs, improved substantially after a period of sleep – and this improvement was greater than after an equivalent period of wakefulness.

As the Journal of Experimental Psychology: General reports, a team led by University of Michigan’s Kimberly Fenn and Zach Hambrick selected 250 volunteers and tested them on their recall for pairs of words, as well as on their ability to hold multiple items in working memory at once. They then retested these same volunteers after a period of sleep, and after an equivalent period of wakefulness.

While not all the volunteers’ memories grew stronger after sleep, most showed at least some improvement, especially in working memory:

The correlation between WMC and performance during initial test was not significant, suggesting that the relationship is specific to change in memory due to sleep. This suggests a fundamental underlying ability that may distinguish individuals with high memory capacity.

In short, this may be evidence for a memory system distinct from the one that operates when we’re awake. These findings could eventually help lead to more accurate tests for intelligence – as well as more effective study methods tailored to an individual person’s memory style.

It also reminds me of a point I like to raise in discussions about consciousness, dreams, and so on: that the real question, I think, isn’t “What’s the point of sleep?” but “What’s the point of wakeful consciousness?” To put it another way, there’s a lot more going on “behind the scenes” than in the spotlight of consciousness – so exactly what evolutionary problem(s) does subjective consciousness provide a solution to? Seemingly obvious answers spring to mind, I’m sure – but still, this question never fails to provoke some interesting debate.

And on that note, I’m off to do some research for my next article – and then take a nap…for Science!

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