Scientists have long puzzled over the links between memory, sleep and learning. Researchers at Northwestern University, Evanston, Illinois asked 12 participants to associate 50 images with a random location on a computer screen. Each image was paired with a sound e.g. a stick of dynamite was paired with the sound of an explosion while a shattering wine glass was paired with the sound of breaking glass. 45 minutes after they had finished learning the participants were sent to lie in a darkened room. Once they had fallen asleep they were played some of the sounds associated with the objects although none of them remembered hearing them. However, when the participants were tested again they were more accurate at remembering the location of objects whose sounds they had heard while they were sleeping.
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