Sensory deprivation is a situation where people are deprived of the usual stimulation of their senses encountered in daily life. Apparently when people are isolated from sensory stimulation as far as possible in a laboratory they quickly become bored and then start to hallucinate. It may be that when people have nothing in their environment for their brains to work on and make sense of they feel a need to provide their own sensations and make sense out of nothing.
Definition