鈥淪leep-learning鈥�, we observed in our 5 March 1970 issue 鈥渋s big business in the Soviet Union.鈥� A slew of studies, experiments and trials from behind the Iron Curtain showed an enthusiasm for pumping information, such as lists of foreign words, into people鈥檚 brains while they slept. Our article found that several Russian civil and military establishments were setting up dormitory facilities to practise the method. However the fervour wasn鈥檛 backed by much evidence.
We looked at an investigation into sleep-learning, led by D. J. Bruce, at London鈥檚 Maudsley Hospital. The aim of the experiment was to find out what effect the technique would have on participants鈥� abilities to learn a list of 15 pairs of nonsense syllables.
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To test this, one group was played sounds of these pairs, a second group was exposed to scrambled pairs of the syllables, and the third was played music- all while they slept.
It didn鈥檛 work. There was no discernible difference between the three groups鈥� abilities to learn the syllables on awakening.
But Bruce鈥檚 experiment focused on deep sleep which is different to the type typically used in Russian sleep-learning. 鈥淭here the input of information is deliberately restricted to the lightest phases of sleep, the drowsy period when the subject is suspended between consciousness and oblivion,鈥� we noted.
While the Maudsley experiment poured cold water on the idea that all you have to do to become a genius is to replace your hot-water bottle with a tape recorder, 鈥渋t by no means writes the obituary of what has become known 鈥� perhaps unfortunately 鈥� as sleep-learning鈥�, we concluded.
We were right not to be too dismissive. A 2012 study showed that sleeping people can learn to associate specific sounds and smells. Others have demonstrated that presenting sounds or smells during sleep boosts performance on memory tasks 鈥� providing the same sensory cues were present during initial learning.
But perhaps we are looking at this idea from the wrong angle. An idea growing in popularity is that sleep evolved, not just to process the day just gone, but to make room for the next day鈥檚 memories. 鈥淪leep is the price we pay for learning,鈥� said Giulio Tononi at the University of Wisconsin-Madison, who developed the idea.
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