title: An empirical study of the traditional Mach card effect.
abstract: The traditional achromatic Mach card effect is an example of lightness inconstancy and a demonstration of how shape and lightness perception interact. We present a quantitative study of this phenomenon and explore the conditions under which it occurs. The results demonstrate that observers show lightness constancy only when sufficient information is available about the light-source position, and the perceptual task required of them is surface identification rather than direct colour-appearance matching. An analysis and comparison of these results with the chromatic Mach card effect (Bloj et al 1999 Nature 402 877-879) demonstrate that the luminance effects of mutual illumination do not account for the change in lightness perception in the traditional Mach card.
authors.affiliation: Department of Optometry, University of Bradford, UK. m.bloj@brad.ac.uk
authors.forename: Marina G
authors.initials: MG
authors.lastname: Bloj
authors.forename: Anya C
authors.initials: AC
authors.lastname: Hurlbert
mesh_terms: D003118:Color Perception / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology; D006801:Humans; D010775:Photic Stimulation; D011581:Psychological Tests; D011601:Psychophysics; D014796:Visual Perception / Q000502:physiology*