THE COMPONENTS OF THE POGGENDORFF ILLUSION

Abstract

An explanation of the Poggendorff misalignment illusion in terms of 3 basic components, the horizontal-vertical, longitudinal-transverse and obtuse angle effects, is proposed. These effects may singly or jointly give rise to an apparent elongation-contraction of the space between the aligned elements with consequent change in apparent oblique direction. Experimental evidence for the involvement of the 3 components in various combinations and for modification of perceived direction between the transversals is presented. The illusion in various forms of the Poggendorff figure can be accounted for by the involvement of 1 or more of the 3 components, each of which can be demonstrated independently of the illusion. Other classical illusions, including the Mueller-Lyer, might also be analyzed in terms of basic components.