Can You Learn While You're Asleep?

Aug 28, 2012
Originally published on August 31, 2012 9:44 am

If you're a student, you may have harbored the fantasy of learning lessons while you sleep. Who wouldn't want to stick on a pair of headphones, grab some shut-eye with a lesson about, say, Chinese history playing in his ears — and wake up with newly acquired knowledge of the Ming Dynasty?

Sadly, it doesn't work. The history lesson either keeps you from going to sleep, or it doesn't — in which case you don't learn it.

But researchers may have taken the first baby step to making the fantasy come true: In an unusual experiment published in Nature Neuroscience, researchers Anat Arzi, Ilana Hairston and others showed that people are capable of learning simple lessons while fast asleep.

The researchers sprayed volunteers with pleasant and unpleasant smells while they were fast asleep. Exactly like people who are awake, the sleeping volunteers took bigger breaths when there was a pleasant smell and a smaller breath when there was an unpleasant smell.

The researchers also paired each kind of smell with a particular sound. After repeated pairings of, say, a pleasant smell with a high-pitched beep, the researchers played the high-pitched beep without the smell: They found the volunteers took a big gulp of air. At least subconsciously, in other words, they were expecting the pleasant smell.

The researchers similarly paired an unpleasant smell – rotting fish – with another kind of tone. After repeated pairings, the tone alone caused the volunteers to take a smaller breath.

The phenomenon is known as conditioning, a simple form of learning made famous by Ivan Pavlov and his dog.

When the volunteers woke up, the researchers played the different tones to them. They found that the high-pitched beep caused the volunteers to take a big breath and the low-pitched beep caused the volunteers to take a small breath.

In other words, the conditioning lesson learned while the volunteers were asleep stayed with them after they awoke. Interestingly, the volunteers had no conscious recollection of having learned anything while they were sleeping.

Hairston said the research could help unlock the effects that sleep has on different brain processes. It's been known for a while that a nap can help cement things you've learned; Hairston said the sleep mechanisms that consolidate knowledge may explain why volunteers in the current experiment were able to bring what they learned during sleep into waking hours.

Practical applications of the conditioning technique are still far off, of course. But speculating about potential future uses, Hairston said: "A medical student can learn a list of body organs. You can perhaps pair different organs with smells. So you pair the thalamus with the smell of lemon, and the hypothalamus with the smell of orange blossom. When you wake up, you will have a better recollection of that list!"

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Next, we have the real-world version of a widespread fantasy - the idea that you could somehow learn while sleeping; that students returning to school this time of year could prep for a test in bed; that busy adults might play a tape, and learn French during nap. Real life does not really work like the fantasy. But Shankar Vedantam, NPR's science correspondent who looks at interesting social science research, has found some research that points in that direction.

Shankar, good morning.


INSKEEP: So what's the idea here?

VEDANTAM: Well, we've known for a very long time that sleep can help you consolidate the things that you have already learned. So I spoke with a sleep researcher. Her name is Ilana Hairston. She's at the Academic College of Tel Aviv. Here's how she put it to me.

ILANA HAIRSTON: If you learn something in the morning, in the evening your learning has improved. But it's also been shown, this effect can be actually enhanced if you take a nap during the day.

INSKEEP: Wait a minute. So you're saying you learn something, then you take a nap; and after the nap, you better understand what you learned before the nap. That's what she's saying?

VEDANTAM: That's exactly what she's saying. Now, the question that she wanted to answer is, it's clear that sleep can consolidate what you have already learned. But is it possible that you can actually learn something new while you're sleeping? And of course, that goes right back to the fantasy you laid out at the top of this - which is a fantasy that I had throughout my student days - which is, I could just stick a pair of headphones on my ears, go to sleep, wake up and say hey, I've learned the history of the Ming Dynasty.

INSKEEP: OK. Has anybody tried this?

VEDANTAM: So, Hairston has conducted an experiment that I would have to say is the first baby step in that direction. She's found that the brain can learn fairly simple things while people are fast asleep. So here's the experimental setup. She and her colleagues bring a bunch of people into the laboratory, a sleep laboratory, hook them up with meters. Now, when the volunteers are completely fast asleep, the researchers sprayed them with a pleasant smell - like the smell of shampoo or deodorant.


VEDANTAM: And they found that the volunteers took a deep breath. And that's exactly what people do when they're awake. Now, every time there was a pleasant smell, the researchers also played a beep - like, a high-pitched beep, right? And they paired the pleasant smell with the beep, repeatedly. And they found that after 10 or 15 times of doing this, when they just played the high-pitched beep, the volunteers took a big breath.

INSKEEP: This is like that famous experiment with Pavlov and the dog, and the dog's mouth watering when the bell goes off - and that sort of thing.

VEDANTAM: Exactly. So it's called conditioning, and it's a very basic form of learning. Now, by the way, they also did the same thing with unpleasant smells. They used rotten fish, and they had a low-pitched beep. And this time, they found that the volunteers took a smaller breath when they had the unpleasant smell.

Now, the million-dollar question is, it's clear that the brain can learn to associate smells and sounds while it's asleep. But does this learning carry over into when the people are actually awake? So the researchers waited for the volunteers to wake up, and then they played these sounds to the volunteers. And they found that when they played the high-pitched beep, the volunteers took a big breath. They played the low-pitched beep; the volunteers took a small breath.


INSKEEP: OK. So it does carry, then, over to when you're awake. But that's a very, very simple - very, very basic form of learning; probably a little bit simpler than learning the Ming Dynasty.


VEDANTAM: It is a lot simpler than learning the Ming Dynasty. There were two interesting things about this. The first is, the volunteers had no conscious recollection of having learned anything at all. They woke up; they heard these sounds and took either a big breath, or a small breath.

INSKEEP: Mm-hmm.

VEDANTAM: Now, I asked Dr. Hairston about what the practical implications were; how quickly students would be able to utilize this research to essentially, supplant their entire educations. Here's what she told me.

HAIRSTON: A medical student can learn a list of body organs. You can - perhaps pair different organs with smells. So you pair the thalamus with smell of lemon, and the hypothalamus with smell of orange blossom. When you wake up, you will have a better recollection of that list.

INSKEEP: So they haven't quite figured out the practical applications.

VEDANTAM: Well, I think the practical implications, in terms of actually supplanting an entire education, is way down the road. But what this is, is a proof-of- concept study that shows that at least at a basic level, the brain is capable of learning new stuff while you are completely- fast asleep.

INSKEEP: NPR science correspondent Shankar Vedantam, who is refusing to confirm or deny whether he reported this entire story while asleep. Shankar, thanks very much.


INSKEEP: Shankar Vedantam regularly joins us to talk about interesting social science research. You can follow him on Twitter @Hidden Brain. And while you're at it, you can follow this program @MORNING EDITION and @nprinskeep. You are getting very sleepy.


INSKEEP: (Whispering) It's MORNING EDITION, from NPR News. Transcript provided by NPR, Copyright NPR.