If you put your history notes under your pillow and sleep on them the night before an exam, will you do any better in the exam? Most of us have hoped this might help. However, knowledge can't go through the pillow into your brain. But that doesn't mean you can't learn while you are asleep.

    Scientists aren't exactly sure how it works, but they have discovered that the brain can learn things during sleeping hours.

    In one experiment, researchers gave German speakers some Dutch words to learn. Then, they divide them into three groups. The researchers played the Dutch words for people in Group 1 while they were asleep, without telling these German speakers what they were doing. The sound was low. So it didn't wake them up, and only the newly introduced words were used.

    Another group listened to the same words while they were awake. The researchers found the people in Group 1 were better able toidentifyand translate the words later. This was true only for the words that were played while they slept. The third group listened to words when they walked. The walkers didn't have the same success remembering the words as the sleeping group.

    The researchers later found that people had more slow wave(慢波的) brain activity all over the night. They said that more slow waves made people have a better memory for the new words.