Size Illusions as a Phenomenon of Limited Information Processing Capacity

Abstract

Abstract The results of a study on the moon illusion are reported, in which the relationship between the illusion, vision and the distance of the horizon have been investigated. The illusion is explained on the basis of a model derived from information theory. Due to the limited channel capacity of the visual system, the size and the resolution of an image are related to each other in such a way, that resolution can only be increased when the size is simultanously reduced. As a result of this constraint, the conspicuity area has to be reduced in order to resolve more detail. Assuming that the visual image is projected onto what is effectively an internal visual memory screen, the size illusion can be explained. A mathematical expression is derived which is fitted to the results of various experiments performed by several other authors in order to measure size constancy. Based on this model two versions of the moon illusion are discussed, as well as their relationship to atmospheric effects and to perspective. The horizon-distance hypothesis is regarded as a special case within this more general model.