Visual Illusions: Peripheral or Central?

Abstract

ALTHOUGH visual illusions have been studied experimentally for more than 100 years, there is still controversy about their explanation. Some authors claim that most geometrical illusions are caused by peripheral factors such as retinal mechanisms. Ganz¹, for example, suggests that those illusions involving intersecting lines (Zöllner, Poggendorff and Müller-Lyer) can be explained by lateral inhibition producing a relative shift in the positions of the intersecting lines. Other authors favour a more “central” explanation such as apparent perspective cues suggesting depth in the figure², or inappropriate constancy scaling³. Still others favour an explanation in terms of general principles such as convergence–divergence⁴.