Varying the strength of the Munker-White effect by stereoscopic viewing

In the Munker-White effect grey target bars appear lighter when they are flanked by white bars, and darker when they are flanked by black bars. It is shown that the effect is enhanced if the patterns are presented stereoscopically so that the grey bars appear either behind the grating, in which case they are seen as a rectangle that is occluded by the white bars of the grating, or in front of the grating, so that they form a transparent rectangle. These results are explained in terms of object perception: contrast enhances differences between an object and its surroundings, whereas assimilation reduces differences within an object.