Reluctant students and sleepyheads take note: a study conducted at the universities of Zurich and Fribourg has shown that German-speaking students are better at remembering the meaning of newly learned Dutch words when they hear the words again in their sleep. "Our method is easy to use in daily life and can be adopted by anyone," says study director and biopsychologist Björn Rasch. However, the results were obtained in strictly controlled laboratory conditions. It remains to be seen whether they can be successfully transferred to everyday situations.
In their trial, which has been published in the journal Cerebral Cortex, Thomas Schreiner and Björn Rasch asked 60 volunteers to learn pairs of Dutch and German words at ten o'clock in the evening. Half of the volunteers then went to bed. While they slept, some of the Dutch words they had learned before going to bed were played back quietly enough not to awaken them. The remaining volunteers stayed awake to listen to the Dutch words on the playback.
The scientists awoke the sleeping volunteers at two in the morning, then tested everyone's knowledge of the new words a little later. The group that had been asleep were better at remembering the German translations of the Dutch words they had heard in their sleep. The volunteers who had remained awake were unable to remember words they had heard on the playback any better than those they had not.
Reinforcement of spontaneous activation
Schreiner and Rasch believe that their results provide further evidence that sleep helps memory, probably because the sleeping brain spontaneously activates previously learned subject matter. Playing this subject matter back during sleep can reinforce this activation process and thus improve recall. For example, a person who plays a memory card game to the scent of roses, and is then re-exposed to the same scent while asleep, is subsequently better at remembering where a particular card is in the stack, as Rasch was able to show in another study a few years ago.
Schreiner and Rasch have now observed the beneficial effect of sleep on learning foreign words. A certain amount of swotting is still needed, though. "You can only successfully activate words that you have learned before you go to sleep. Playing back words you don't know while you're asleep has no effect," says Schreiner.