A number of reports have been published on the effects of drastic and prolonged reduction of normal environmental stimuli on human beings. Dramatic phenomena, such as depersonalization, hallucinations, thought disturbances, and other symptoms customarily associated with mental illness, have occurred under such conditions. Many investigators have regarded conditions of sensory deprivation as inherently stressful, and their published observations have placed great emphasis on the pathological consequences of prolonged sensory deprivation for normal subjects. In a representative study, Wexler, Mendelson, Leiderman, and Solomon9(1958) subjected normal subjects to perceptual and sensory deprivation for periods up to 36 hours. They observed a variety of pathological events in these subjects, such as "pseudosomatic delusions, illusions, or hallucinations," and noted that "all subjects showed impaired ability to concentrate, distortions in time judgment, and degrees of anxiety." Further, they described sensory deprivation procedures as useful in inducing stress and in producing psychotic-like symptoms. In