Complement

to reduce stimulation to a minimum or to achieve "optimal" states of stimulation. The author's contention is that there is a drive for optimal levels of stimulation that leads organisms to avoid states where sensory variation is either too high or too low. This "sensoristatic drive" is a state of cortical arousal that is monitored by the reticular formation which serves as a regulator adjusting input-output relations. This formulation is applied to studies of the effects of reduction of variation in stimulation (perceptual deprivation) or reduction in absolute levels of stimulation (sensory deprivation) in terms of seven propositions derived from the "sensoristatic drive model": (1) conditions of reduced sensory input will result in changes in physiological activation level; (2) the sensoristatic drive is induced by conditions of restricted sensory variation and increases with time and amount of deprivation; (3) when conditions of sensory restriction disturb the sensoristatic balance the organism will exhibit gross disturbances of functioning; (4) when stimulus variation is restricted, central regulation of threshold sensitivities will serve to lower sensory thresholds; (5) organisms will exhibit evidence of learning in situations where the only apparent reinforcement is a change in sensory variation; (6) there are individual differences in the need for sensory variation that may be due partially to early postnatal levels of stimulation; and (7) perceptual deprivation leads to a more intense sensoristatic drive than sensory deprivation. Much of the experimental literature is examined in chapters dealing with a physiological and threshold change; changes in cognition and learning; changes in perceptual and motor performance; affective changes and individual differences. In addition, there is a chapter dealing with the effects of social deprivation and two chapters devoted to the presentation and evaluation of the theory. The breadth of evidence covered makes this book a valuable source book in a field that has "grown like Topsy." Many recent sources, some yet unpublished, some obscure, are drawn upon. There is, however, a notable absence of critical evaluation of material, and the discussions at the end of each chapter select those sources of data that confirm one or the other of the theoretical propositions set forth. While this book serves to document changes introduced by sensory restriction, there is little to help us in figuring out the behavioral mechanisms involved in such effects. While much weight is placed on the drive concept, there is little discussion of how and when states of high drive will serve to influence adaptive behaviors. JOSEPH GLICK