It May Actually Be Possible to Learn in Your Sleep

There are some pieces of dubious science whose debunkings are also real bummers. Brain training games, for example. Power posing, or the idea that just standing a certain way can make you more confident and assertive. That thing where you put on a language tape when you go to bed and wake up in the morning speaking fluent French. All hacks that would make life just a little easier, if only they were actually legitimate.

That last one, especially, has been the subject of plenty of wishful thinking over the years. Friends fans might remember that episode when Chandler tries a smoking-cessation hypnosis tape while asleep; in the 1920s, as the Washington Post noted recently, a device called the “Psycho-phone” claimed to help users lose weight or conquer love problems by playing encouraging records as they slept.

It’s easy to understand the appeal of hypnopedia, or sleep learning — just think of all the time it would free up during your waking hours, and all the unpleasant tasks you could delegate to your subconscious. But while the idea that we can absorb new facts or skills during sleep has been thoroughly discredited, a study published yesterday in the journal Nature Communications found that we do make memories.

For the study, the authors recruited 20 volunteers with no history of sleep disorders and played white noise as they slept. Sprinkled throughout the recordings were a series of split-second acoustic patterns, each one so quick so to be nearly undetectable. Later, when the participants were awake, the researchers played the same recordings and instructed their subjects to pick the sequences out of the white noise — and they did, successfully, at a rate better than if they’d just randomly guessed.

The key here, neuroscientist and study co-author Thomas Andrillon told the Post, is in the complexity of the information that’s being presented:

The lack of meaning worked in their favor; sleepers can neither focus on what they’re hearing nor make explicit connections, the scientist said. This is why nocturnal language tapes don’t quite work — the brain needs to register sound and semantics. But memorizing acoustic patterns like white noise happens automatically. “The sleeping brain is including a lot of information that is happening outside,” Andrillon said, “and processing it to quite an impressive degree of complexity.”

A caveat: The finding only applied to certain parts of the sleep cycle. For participants in the deepest stage, Andrillon explained to the paper, sequences “presented during non-REM sleep led to worse performance, as if there were a negative form of learning” — suggesting, he argued, that memories are alternately pruned or strengthened depending on the sleep stage, a reconciling of two dueling hypotheses on the purposes of sleep. In other words: You may not be able to check things off your to-do list while sleeping, unfortunately, but your brain is still hard at work in ways we’re just beginning to understand.

It May Actually Be Possible to Learn in Your Sleep