Volunteer subjects, exposed to an environment in which visual, auditory, and tactile sensations are reduced as much as possible, experience a variety of subjective disturbances ranging from anxiety and oppression to illusions and hallucinations. Investigators using different methods1-4 have reported wide variations in results. At the present time the fundamental determinants of the phenomena observed are still in question. In previous reports from this laboratory,2,3 it has been suggested that 3 factors must be considered in studies of sensory deprivation: sensory deprivation per se, concomitant social isolation, and concomitant reduction in kinesthetic cues due to immobilization. We have directed experimentation to assess the role of each of these as separately as possible. A recent paper3 described work in which meaningless visual stimulation (a flashing light) was given to subjects in a previously standardized sensory deprivation situation; the findings sug