Think back to college. It’s the night before a final exam and you’re not as prepared as you’d like. After a few hours of cramming, your study buddy quizzes you on some 100 years of intellectual history, or maybe a shit-load of formulas and you get about half the questions right. Even with a curve, 50 percent won’t get you a passing grade. Should you sleep on it or study more?
Both motherly wisdom and sleep studies say “go to bed.” Among other benefits, getting that #hardeight will help you remember the dates and theories floating around in your mind.But, how exactly will sleep enhance your memory of that information? Does rest merely keep you from forgetting the 50 percent of material you’ve already locked in? Or, is there a chance you’ll wake up, open that blue book and be able to retrieve the facts and figures that didn’t come to mind last night?
Yes, there’s a chance, according to U.K psychologist Nicolas Dumay. The precise ways in which sleep supports memory is a source of debate, but Dumay believes his research, published this week in the journal Cortex, supports the notion that act of rest not only helps firm-up facts we’ve already locked in, but more impressively, also lets us retrieve information we never quite learned while awake.
A bit of background: According to one theory, deep-sleep primarily runs “retroactive interference,” meaning it acts as an antidote to forgetting. Upon entering deep sleep, this theory says, the brain stops absorbing new information from the outside world, and instead focuses primarily on making sure recently acquired memories stick, a process called memory consolidation.
A different theory — which Dumay favors — disputes the notion of a deep-sleep neural slow-down. Instead, the brain is engaged in “neural replay,” meaning it repeatedly reactivates the original experience of learning new information. Through neural replay, the brain not only prevents already-formed memories from slipping into the ether; it also finishes encoding memories that never quite formed during waking hours, for example that final exam material you blanked on earlier.
In the study, Dumay reanalyzed experiments that linked to sleep to improved declarative memory, meaning the retention of factual information (rather than experiences or skills). In one of the experiments, study participants learned a series of made-up words that sounded similar to real words. Shortly afterwards, they demonstrated their new knowledge by recalling and defining as many terms as they remembered. Then, half the participants stayed up for the next ten some-odd hours, while the other half got sleep. After the break, they again showed off their knowledge of the terms. In his reanalysis, Dumay focused on two different recollection measures. First, he noted which words they knew among those they’d correctly identified the first time. Additionally, he took account of the words they got right that they hadn’t been able to recall during the first vocab-test.
Participants who slept between tests performed better overall. But the results were more pronounced with regard to words people hadn’t remembered in the first place. Meaning, in some sense, we can form new memories while we sleep. In other words, sleeping on it really does make a difference.