title: Color appearance depends on the variance of surround colors.
abstract: BACKGROUND
  The perceived color at each point in a visual scene depends on the relationship between light signals from that point, and light signals from surrounding areas of the scene. In the well known phenomenon of simultaneous color contrast, changing the overall brightness or hue of an object's surround induces a complementary shift in the perceived brightness or hue of the object's color. Color contrast is thought to contribute to color constancy with changes in illumination.
  
  
  RESULTS
  We report a new type of simultaneous color contrast, in which changing only the variance (i.e. contrasts and saturations), but not the mean, of colors in a test spot's surround induces a complementary shift in the perceived contrast and saturation of the test spot's color. Objects appear much more vivid and richly colored against low-contrast, gray surrounds than against high-contrast, multicolored surrounds.
  
  
  CONCLUSIONS
  Color appearance depends not just on the mean color of the surround, but also on the distribution of surround colors about the mean. This novel form of simultaneous color contrast is inconsistent with a variety of models of color appearance, including those based on sensitivity regulation at the receptor level, and those in which the effects of complex surrounds on color appearance can be reduced to adaptation to the illuminant or induction from a homogeneous 'equivalent surround'. It tends to normalize the gamut of perceived colors in each visual scene and may also contribute to color constancy under viewing conditions that affect contrast.
authors.affiliation: University of California at San Diego, Department of Psychology, La Jolla 92093-0109, USA. robrown@ucsd.edu
authors.forename: R O
authors.initials: RO
authors.lastname: Brown
authors.forename: D I
authors.initials: DI
authors.lastname: MacLeod
mesh_terms: D003118:Color Perception / Q000502:physiology*; D003119:Color Perception Tests; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008027:Light; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology; D011897:Random Allocation; D014741:Video Recording