Just before you climb under your duvet, you carefully prepare your room. You sprinkle a few drops of incense on your pillow, put on some headphones, and place a strange-looking band over your scalp. Then you go to sleep. The ritual takes just a few minutes, but you hope this could accelerate your learning of a diverse range of skills: whether you are trying to master the piano, tennis or fluent French. You won’t recall a single aspect of the night’s “training” – but that doesn’t matter: your performance the next morning should be better, all the same.

The idea of learning as you sleep was once thought very unlikely, but there are several ways – both low- and hi-tech – to try to help you acquire new skills as you doze. While there is no method that will allow you to acquire a skill completely from scratch while you are unconscious, that doesn’t mean that you still can’t use sleep to boost your memory. During the night, our brain busily processes and consolidates our recollections from the day before, and there could be ways to enhance that process.

Given that we spend a third of our lives in the land of nod, it is little wonder that sleep learning has long captured the imagination of artists and writers. In most incarnations, it involved the unconscious mind absorbing new information from a recording playing in the background. In Aldous Huxley’s Brave New World, for instance, a Polish boy learns English after having slept through a radio lecture by George Bernard Shaw; the authoritarian government soon uses the same technique to brainwash its subjects. More recently, in The Simpsons, Homer buys a tape to subliminally reduce his appetite as he sleeps, only to find that it is instead changing his vocabulary. When his wife, Marge, asks if his diet is working, the normally inarticulate Homer replies: “Lamentably, no. My gastronomic rapacity knows no satiety”.

Bad science

In reality, this particular kind of sleep learning is almost certainly impossible. Although some early studies suggested that subjects could pick up some facts as they slept, the researchers couldn’t be sure that they hadn’t just awoken to listen to the recording. To test those suspicions, Charles Simon and William Emmons attached electrodes on the scalps of their subjects, allowing them to be sure that they only played the tapes once the subjects were dozing. As they had suspected, the subjects learnt nothing once they had dropped off. The results were published in the 1950s, but entrepreneurs over the years have still tried to cash-in on the attraction of effortless learning with various products – even though their methods had no scientific basis.