When you go to sleep tonight, put a book under your pillow. When you wake up tomorrow morning, you’ll have its contents memorized.
OK, so that probably won’t work.
But don’t lose hope just yet: It turns out there actually are a few things you can learn — or at least improve your grasp of — while you snooze. Most of them depend on one thing: sound.
Here are some of the skills you may be able to sharpen in your sleep:
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1. Foreign words.
In a recent experiment, scientists had native German speakers start learning Dutch, beginning with some basic vocab. Then they asked them to go to sleep.
Unbeknownst to the dozing Germans, while they slept, the researchers played the sound of some of those basic words to one group of them. The other group was exposed to no such sounds. Later on when they were tested on the words, the group who’d listened to them overnight was better able to identify and translate them.
To make sure the findings were tied to sleep — and not just the result of people hearing the words — they had another group listen to the words while they did something else while awake, like walking. The walkers didn’t recall the words nearly as well as the sleepers.
2. Musical skills.
In another study, researchers taught a group of people to play guitar melodies using a technique borrowed from the video game Guitar Hero. Afterward, all the volunteers got to nap. When they woke up, they all were asked to play the tune again.
Unbeknownst to the sleeping participants, one group was played the same melody they’d just learned as they slept. The other group was not. The volunteers who’d been played the sound while they napped — even though they had no memory of it — played the melody far better than those who didn’t hear it as they snoozed.
3. Where you put something.
In a 2013 study, researchers had 60 healthy adults use a computer to place a virtual object in a particular location on the screen. When they picked a location and placed the object there, they heard a specific tune. Then, they did two experiments in which they had the participants nap for 1.5 hours. During the first nap, participants dozed as usual, with no sounds playing. During the second nap, the tune that was played when they were placing the object was played again — though none of them reported hearing it.
Not surprisingly, after either nap, people’s memories faded. But their memories faded less when they’d been exposed — even sub- or unconsciously — to the sound that had been played when they’d placed the item. Interestingly, their memories were sharper still when they’d been told the virtual object was of “high value.”