When you tidy your messy bedroom，it gets a lot easier to find things.Dreams may work the same way for a messy brain，helping you learn by organizing memories and ideas. To test how much dreams can help learning，Robert Stickgold had some students play a shapefitting game called Tetris (俄罗斯方块) for a few hours and then go to sleep.Soon they were dreaming of falling Tetris shapes.Interestingly，the worst Tetris players had the most Tetris dreams and improved their game the most.Similar tests have shown the same results for all kinds of skills. As we dream，many important tasks are getting done.The brain decides what to keep and what to forget.It is connecting new experiences to older learning.In fact，the brain is learning all night long. Another important task of dreams may be to help us deal with emotions (情绪)．At night，emotions are in the driver’s seat.People who have had an upsetting experience often dream about it afterward.Often the dream event changes somehow—another way the brain tries to make the memory less upset.So if your best friend moves away，you might dream that you’re the one who’s moving.In fact，dreams have a proven power to improve mood，and people who dream about what’s bothering them usually feel better sooner than those who don’t. Everybody dreams for a couple of hours every night—in the course of your life，you’ll spend about 25 years asleep and 6 years dreaming.There’s probably no single answer to the question why we dream，but there doesn’t have to be.One dream might help you remember your math facts，while another might lead to a new invention，or give you a fun，crazy story to tell your friends.It’s all in a night’s work for our busy，mysterious brains. 小题1:Robert Stickgold’s test shows that________.
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