Dreaming is a form of mental activity that occurs during sleep. The nature of dream activities has been characterized by many clinical and laboratory studies. These studies are more perceptual than conceptual: things are seen and heard rather than being subject to thought. Visual perception is present in almost all dreams, and auditory experience is 40 to 50%, but dreams are not necessarily visual imagery. Congenitally blind people dream in auditory and sensory-motor modes. One difference between waking and dreaming consciousness is that the ....