This investigation was designed to subject to systematic study the hypothesis that the effects of sensory isolation are due to the removal of meaningful information relevant to the solution of an internally perceived problem. Three experimental conditions were used in which auditory input was the only experimental variable not held constant. The three varieties of auditory input were: 1) white noise (no meaning); 2) recordings of playlets, puzzles, jokes, etc. (meaning present); and 3) tape recordings played backward (no meaning).The paper reports comparative effects produced in ten subjects in each condition as obtained from subjects' reports and psychological tests. The results suggest that heightened imagery seen in sensory isolation is related to depatterning of input, but that disturbances of concentration, sleep-wake confusion, emotional lability, impairment of reality testing, errors of visual retention and certain other cognitive and perceptual impairments seen are related to the absence of meaningful input.