The Effect of Articulation and Shape Similarity on the size of the Berrary' s illusion

Abstract

In the Benary-cross illusion (1924), two physically identical gray surfaces appear to have different shades of gray, although they border equally with black and white. The present experiments tested the effect of articulation and similarity of target with background surfaces, on the size of the illusion. We created 6 different versions of the illusion, in which both articulation and similarity was varied. The results showed that illusion size increases with increased articulation. These results are taken to support accounts of the illusion based on lightness computations within perceptual groups, and not physiological theories based on peripheral mechanisms of the visual system.