control over the dream

Electroencephalograph studies, measuring the electrical activity of the brain during REM sleep, have shown that young adults dream for 11/2 to 2 hours of every 8-hour period of sleep. Infants spend an average of 50% of their sleep in the REM phase (they are believed to dream more often than adults) a figure which decreases steadily with age. During dreams, blood pressure and heart rate increase, and breathing is quickened, but the body is otherwise immobile. Studies have shown that sleepers deprived of dream-sleep are likely to become irritable and lose coordination skills. Unusually frightening dreams are called nightmares, and daydreams are constructed fantasies that occur while the individual is awake. Studies have demonstrated the existence of lucid dreaming, where the individual is aware that he is dreaming and has a degree of control over his dream. - Columbia Encyclopedia