Perceived lightness depends on perceived spatial arrangement.
The perceived shade of gray depends primarily on the luminance relationship between surfaces percieved to lie in the same plane and not between surfaces that are merely adjacent in the retinal image. This result implies that depth perception must precede lightness perception and that lateral inhibition cannot explain lightness constancy.
D003867:Depth Perception / Q000502:physiology*; D006801:Humans; D008027:Light; D008959:Models, Neurological; D012160:Retina / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*