The right hemisphere in imagery, hypnosis, rapid eye movement sleep and dreaming. Empirical studies and tentative conclusions.

Visual imagery, hypnosis, creativity, dreams, and "imagination" have all been linked conceptually by theoreticians of various schools to an increased influence of right hemispheric processes compared with left hemispheric processes. This paper reviews empirical studies that have addressed the issue of whether there is an increased activation or efficiency of right hemispheric processes during imagery, hypnosis, rapid eye movement sleep, and dreaming. Overall, there is considerable evidence supporting the notion of increased right hemispheric activation in imagery. There is also some evidence supporting this view for rapid eye movement sleep, dreaming, and hypnotic phenomena. For the most part, however, the lack of adequate studies, contradictory or negative findings, and moderating variables make it difficult to draw definitive conclusions at this time.