People who do sleep research tell us that a person is a sort of 'information processor.' We have two ways to use the information we get each day. The first process is used when we are awake. It takes place in the left side of the brain. It is this process that makes us do the things we have to do. It lets us put aside those things that are not a real part of our day's work. The second process happens in the fight side of the brain. This process takes all those bits of information we did not use in the day. It turns them to dreams at night. 'This process is our regular night shift work,' says physiologist Rosalind Cartwright from the University of Illinois. 'At night we put together the bits and pieces of our day, so that we are ready to face the next day.' We have several dreams each night of our lives. About ten minutes after we fall asleep, we begin to go through four stages of sleep. Our sleep gets deeper and deeper. And it gets harder for us to wake up. At the end of the fourth and deepest stage, the process changes. We begin to come back up again through the same stages. The coming back up is called 'rousal' time. It lasts about ten to twenty minutes. We do not wake in this stage. Instead, we go through a stage of vivid dreams. In this stage we do not toss or turn or even snore. The brain temperature and the blood flow get much higher. The body goes as limp as a rag doll. And the large muscles in the arms, legs, and trunk go stiff. The eyeballs begin to move back and forth very quickly, even though the eyes are closed. This is called the stage of Rapid Eye Movement or the REM stage. We go into the REM stage about six times a night. That's once every hour and a half or so. This hour and a half pattern is part of many things in our lives. Lots of body functions happen every hour and a half. Things like stomach contractions (收缩) and hormone secretions (分泌). Why do we dream? Research tells us that dreams can help us with our problems. When we have big problems in the day, we may spend more time in REM sleep at night, because dreams can bring answers to problems. Sleep research reveals ______.