Sleeping is generally considered to be an absolute waste of time. It's a necessity, yes, but you can't actually do anything while asleep. A new study seems to show that it may be possible for humans to learn things while unconscious, potentially making sleep useful for once.
The term "learn" is, unfortunately, being applied in a technical manner that will likely not help you pass any of your classes, unless you have a class in drooling when someone rings a bell. Yes, we're talking about classical conditioning, where animals (humans included) can "learn" to associate one stimulus with another. It's also called Pavlovian conditioning, because of this guy Pavlov who rang a bell every time he fed his dogs, and thusly conditioned them to associate bells with food, meaning that whenever he rang the bell, the dogs would start to slobber all over the place. Gross.
Anyway, this trick works on humans, too, and it also apparently works on humans whether or not we're awake. The study, by Anat Arzi from the Weizmann Institute in Israel, conditioned unconscious humans to associate soft tones with either pleasant or unpleasant scents. Tones and scents were chosen because we don't need to be awake to process either of them, and the conditioning was measured through breathing: when an unconscious human experiences a pleasant scent, he or she will breathe deeply, and if the scent is unpleasant, breathing becomes shallower. After a while, the unconscious humans in the study didn't need the actual scents anymore, and just hearing the tones was enough for them to adjust their breathing patterns.
What this means is that our brains are capable of recognizing and (to some extent) processing external stimuli even while we're asleep. That's great, but what about actual sleep-studying?
According to Nature's Mo Costandi:
Arzi thinks that we could probably learn more complex information while we sleep. "This does not imply that you can place your homework under the pillow and know it in the morning," she says. "There will be clear limits on what we can learn in sleep, but I speculate that they will be beyond what we have demonstrated."
Here's hoping for way, way, way beyond.