Experimental demonstration of the sensory basis of the size-weight illusion

Abstract

An important part of the literature on the size-weight illusion ascribes great importance to expectancies as determinants of the illusion itself. The aim of the experiments reported here was to establish whether the size-weight illusion was sensorial or was caused directly by an expectancy. In Experiment 3, which was the crucial experiment, subjects first looked at an object (from a 3×5, size x weight, factorial design), and then the object was hidden from view. Immediately after the object was hidden from view, the subjects lifted the object and rated its heaviness. It was expected that any possible motor set, or any perceptual or cognitive expectancy, should persist during the lifting. The size-weight illusion did not occur in Experiment 3. Therefore, it was concluded that the illusion was of sensory origin. © 1988 Psychonomic Society, Inc.