Apparent Sizes of Different Shapes and the Facility with which they can be identified

Abstract

EACH of the shapes illustrated in Fig. 1 has the same surface area but when comparing them most people agree that they appear to differ appreciably in size. From a study in which visual stimuli were presented within angular contours, Fisher concluded that “… the apparent features of illusory patterns rather than their actual physical characteristics determine the probability with which near-threshold stimuli can be detected”¹. If this statement refers generally to two-dimensional forms, then circular, square and triangular shapes should be identified in accordance with their apparent rather than their real sizes.