A Mueller–Lyer Illusion Induced by Selective Attention

Abstract

Subjects estimated the length of a horizontal line which was flanked by oblique angles pointing both inside and outside (this figure would be created by superimposing the wings-in and wings-out figures of the Mueller–Lyer illusion). Ignoring the outside wings resulted in an underestimation of the line length of comparable magnitude to that obtained for the wings-in Mueller–Lyer figure. Ignoring the inside wings caused an overestimation of the line length only when the inner and outer wings were of non-corresponding orientations. These results emphasize the role of cognitive factors in the Mueller–Lyer illusion.