You spend a third of your life asleep. Wouldn’t it be great if you could put that time to use? New research suggests you can. A recent study, published in Nature Neuroscience, contains groundbreaking findings that may change the way we view our time in bed. For the first time, researchers demonstrate that you can learn new information while you sleep and with no conscious knowledge of it.
Learning while you sleep isn’t a new idea. But while several studies have shown that you can enhance prior learning during sleep, until now no studies have shown that you can learn new information during sleep. One problem with demonstrating new learning in sleep is that you can’t test for it without waking up the subject.
To skirt this problem, a team of researchers in Israel took advantage of a reliable and sneaky measurement tool—the nose. The nose is useful because humans tend to sniff more when a pleasant smell is present, and less for a bad smell. Sniffing, therefore turns out to be a measurable and reliable indicator of odor preference. And odor preference can be used to measure learning.
Add to that the fact that smells don’t tend to wake people up, and you’ve got a way to measure learning in sleep. The researchers exploited this and measured the amount of sniffing among subjects in the presence of various odors, from shampoo to rotten fish. Finding that, indeed, sleeping subjects sniffed less for rotten fish, they then used sniffing to measure learning in an ingenious sleep study.
There were 55 subjects in total. After suiting up for an EEG recording (to ensure that they were actually asleep), subjects went to sleep for the night. While subjects slept, researchers paired odors with different auditory tones. One tone might be paired with the smell of shampoo, another with the smell of rotten fish. Researchers measured the sniff volume for each tone.
Later on in sleep, and again once the subjects awoke, the researchers played the tones without presenting the odor. The big finding? The subjects sniffed as if the odor was present—more for the tones that had previously been paired with good smells; less for tones associated with bad smells.
In other words, the subjects learned to associate a tone with an odor, having no conscious knowledge that they’d been trained. And importantly, they retained this knowledge upon waking.
While the idea of learning while we sleep has been around forever, demonstrating it has been another story. With a little ingenuity, these researchers have made it official. Still, a lot of questions remain. One of the questions they wish to better address is the role of REM versus non-REM sleep in learning. Also, the learning they demonstrated—simple associations—is not rich in immediate practical value.
So what are the limits of what we can learn?
If the learning were more complex, would the new knowledge be accurate or mixed up? How might this affect quality of sleep? Can children learn during sleep? The elderly? Could sleep-learning become psychological therapy for certain disorders or addictions? Treatment for neuro-developmental or neurological conditions? Learning disabilities? The potential usefulness makes this discovery exciting, even if preliminary.
While it’s not exactly enough to suggest you should play recordings of that new language you’ve wanted to learn tonight, this study offers a new research paradigm for studying learning in sleep and opens the door to other studies to address some of the exciting questions that remain. It goes to show that we still have a lot to learn about the power of sleep—not only its importance for our well-being but its unknown range of potential util
