By studying sleeping volunteers, researchers have learned that there are different kinds of sleep. Every night, you go through a number of sleep cycles. Each cycle lasts about 90 minutes and is made up of a period of deep sleep and a period of light sleep. Near the end of the cycle comes a period of what scientists call rapid eye movement , or REM, sleep. During REM sleep, a person's eyes move back and forth as if he or she were watching something. Brain waves show patterns that resemble those seen in a person who is awake. The sleeper's heart and breathing rates may increase. And by waking volunteers during REM sleep, researchers have learned that this is when most dreams occur.
Over eight hours of sleep, most people have three to five dreams, each lasting five to fifty minutes. Usually, most of the dreams are forgotten by morning. But by waking volunteers in the middle of a dream and asking them about it, researchers have learned a lot about dreams. For example, while many people think that they dream in black and white, dreams are almost always in color. Apparently the memory of the colors in our dreams fades even more quickly than the memory of the dreams themselves.
People usually hear as well as see in their dreams. Dreams may even involve the senses of smell and touch. Blind people dream as much as sighted people, but their dreams are made up of sounds, smells, and sensations. During REM sleep, their eyes don't move.
In many dreams, the dreamer simply watches the action. In others the dreamer plays a part. While sleeping, people seldom move or act out their dreams. That's because messages from the brain to the muscles are blocked during REM sleep. (Grolier Book of Knowledge Encyclopedia)
Over eight hours of sleep, most people have three to five dreams, each lasting five to fifty minutes. Usually, most of the dreams are forgotten by morning. But by waking volunteers in the middle of a dream and asking them about it, researchers have learned a lot about dreams. For example, while many people think that they dream in black and white, dreams are almost always in color. Apparently the memory of the colors in our dreams fades even more quickly than the memory of the dreams themselves.
People usually hear as well as see in their dreams. Dreams may even involve the senses of smell and touch. Blind people dream as much as sighted people, but their dreams are made up of sounds, smells, and sensations. During REM sleep, their eyes don't move.
In many dreams, the dreamer simply watches the action. In others the dreamer plays a part. While sleeping, people seldom move or act out their dreams. That's because messages from the brain to the muscles are blocked during REM sleep. (Grolier Book of Knowledge Encyclopedia)