Experiments have been carried out on volunteers to see what happens when all sensations are stopped. This can be done in several ways. One method is to put a man inside a completely isolated room. This room is heavily sound-proofed and absolutely dark. There is no light or sound and the person is instructed just to lie motionless in a bed. People have stayed in rooms such as this for as long as four days. The results of sensory deprivation (SD) vary with the individual. Soon after entering the confinement cell most subjects went to sleep and slept almost without interruption for ten to twenty-four hours. These are gross estimates for there was nothing by which the subjects could determine the time which had elapsed. We know for certain that one subject slept for nineteen hours but insisted that he had had a nap of less than one hour. According to the monitoring microphone, which was capable of picking up the deep breathing of sleep, it seems more likely that most subjects slept all of the first twenty-four hours. We felt that so much sleeping in the first day wasted the effects of confinement, so we started placing subjects in SD early in the morning. We reasoned that after a night' s sleep our confined subject would be unable to dissipate(驱散) the effects of SD by sleeping. Such was not the case. As far as we could determine they went to sleep just as quickly and slept just as long as the previous subjects. We then started entering the subjects at midmorning, midday, and midafternoon. As it turned out, it made no difference when during the day and, presumably, during the night we started the confinement the initial sleep period was always about the same. We had not expected this extended period of initial sleep. In fact, it had seemed reasonable to expect something of the opposite. SD was a very novel situation for our subjects, and as such, we reasoned, it should have occupied them for some time. I had a similar expectation for astronauts during space flight and was greatly surprised to learn that the Russian astronaut Yuri Gagarin had been able to sleep during his space flight around the earth. Other effects were also noted. With no real sensations to work on, the brain makes up all sorts of false information. Many people experience vivid dreams and hallucinations (幻觉). When they are finally taken out of the room into the real changing world of light and sound, they are in a very strange state of mind, ready to believe anything and not really able to make decisions. This passage is mainly about what will happen if sensations were lost.