Twenty young people sleep in a university house, and they volunteer for a memory study. Each one stays for five nights, and the team asks one old question. The brain puts the day's learning into long storage, but that storage can fall fast.
The first two nights are quiet. But the last three nights bring a stormy sea sound at three in the morning. The sound wakes each person for a few seconds. Each person sleeps again, but nobody knows the sound. So their sleep schedule stays the same.
Every person must log their dreams on paper. The dream log then gives the number of dreams. After a quiet night, the log shows three dreams. After a stormy night, it shows one.
So the team runs a memory test each morning. Each person holds ten words. The test finds a big change, and a noisy night cuts the result in half. This finding also builds on an old concept.
So the team tries a quiet plan. Before bed, each person gets warm milk. A soft sound soothes the room, and deep sleep comes back. That drink soothes the body, and the night stays quiet.
The finding stirs talk among sleep doctors, and some doctors want more people. It also stirs a hard question for students. How much of today will they have tomorrow?
One doctor writes about the noise. "A noisy night is not a danger, but it takes your learning away."
The study ends next week. The team plays the sound again in winter. The people keep their milk and their paper, and they now want a quiet night.