Just as alterations of input of energy or matter to the nervous system can cause pathological response, so, too, may alterations of rates of information input into various systems cause pathological response. Recent studies indicate that if information input underload (deprivation) occurs, such pathological function and behavior, and even structural change, may result. Organisms must receive a certain rate of flow of sensory information for normal development and maintenance of adjustment. It is postulated that information overload may produce similar results. Preliminary studies at five levels of organization (cell, organ, individual, group, and social) indicate a falling off of performance after optimal input levels are reached, with the use of certain adjustment mechanisms (perhaps related to psychological defense mechanisms). Miller notes the correspondence between the various levels of performance and adjustment mechanisms and raises the question whether general system characteristics may not clarify the nature of psychopathology.