Why do we sleep? Why do we dream? Many people ask themselves the (a)   , or reason.

There are many (a)   , or opinions, about why people sleep and dream, but scientists don't know if these ideas are correct.

One theory of sleep says that during the day, we use many important chemicals in our bodies and brains. We need sleep to make new chemicals and (a)   , or fix, our bodies.

One piece of (a)   for the "Repair Theory" is that our bodies produce more of a chemical that helps us grow while we sleep.

Our bodies produce more of a growth (a)   (a chemical that helps us grow) while we sleep.

Dreaming happens only during one (a)   , or period, of sleep - REM (Rapid Eye Movement ) sleep.

REM (Rapid Eye Movement) sleep (a)   about every 90 minutes and lasts for about 20 minutes.

Many cultures believe that dreams can predict the future - they can tell us what is going to happen to us. (a)   , some people believe that dreams are only a form of entertainment.

__________ such as Sigmund Freud say that dreams are not predictions of the future. __________ have strong beliefs about dreams. (兩格的答案相同, 填入一個代號即可!)

(a)  

Freud, who wrote around the year 1900, said that dreams can tell us about our (a)   - feelings and desires, or wishes.

Freud believed that our dreams are full of (a)   . In other words, things in our dreams mean other things.

Freud thought that dreams are about from our past, from our (a)   . Other psychologists say no.

We still don't know why we dream. However, there is interesting new evidence from (a)   , or studies, about the brain.