We usually believe what our brain tells us, but there are some amazing facts which show that the brain tricks us. As a result, we think we can see something that is not actually there or we ignore（忽视）things that actually are there.

 Scientists Daniel Simons and Christopher Chabris have researched this phenomenon（现象）, which they call “change blindness”. Their experiments show how we sometimes just do not see what is in front of our eyes because           42          .

 Here is one of their most famous experiments. In this experiment, the participants（参与者）were shown a video of two groups of people (one group in white T-shirts and one group in black T-shirts) who passed basketballs around in a hallway. Each group had three members. Simons and Chabris asked the participants to count how many times the white team passed the ball. While the two teams were passing their balls around, a person dressed up as a big bear walked through the group and stopped to look at the camera. Simons and Chabris found that about half of the research participants did not notice the big bear.

Everybody dreams. But only some people remember their dreams. Our dreams often include all the senses —- smells, sounds, sights, tastes and things we touch .Sometimes we dream the same dream over and over again.

    Early in the twentieth century, two famous scientists developed their personal ideas about dreams. Austrian psychiatrist (奥地利心理学家) Sigmund Freud wrote a book called "The Interpretation (诠释) of Dreams" in 1900. Freud believed people often dream about things they want but can't have. Swiss (瑞士) psychiatrist Carl Jung worked closely with Freud for several years, but he believed dreams provide solutions to problems we face when we are awake.

    Other researchers are studying how dreaming helps our bodies work with problems and very sad emotions (感情). Robert Stickgold is a professor of psychiatry (心理学教授) at Harvard University in Massachusetts. He says that when we dream, the brain is trying to make sense of the world. He does not agree with Sigmund Freud that dreaming is the way we express our hidden feelings and wishes.

    Scientists believe it is important to keep researching dreams. Doctor Stickgold says it's more than one hundred years since Sigmund Freud wrote his important book about dreaming. Yet there is still no agreement on exactly how the brain works when we are dreaming or why we dream.