Illusory contour lightness: a neglected possibility.
When the area occupied by a typical sharp-edged illusory figure is outlined physically, some illusory lightness survives within the contours as an example of figure-ground contrast. This general phenomenon may therefore account for the direction of the apparent alteration in lightness found within many illusory figures, but it cannot account for the magnitude of that alteration.
D005556:Form Perception; D006801:Humans; D007088:Illusions; D008029:Lighting; D009903:Optical Illusions; D014796:Visual Perception