Parallel detection of violations of color constancy

The perceived colors of reflecting surfaces generally remain stable despite changes in the spectrum of the illuminating light. This color constancy ca n be measured operationally by asking observers to distinguish illuminant c hanges on a scene from changes in the reflecting properties of the surfaces comprising it. It is shown here that during fast illuminant changes, simul taneous changes in spectral reflectance of one or more surfaces in an array of other surfaces can be readily detected almost independent of the number s of surfaces, suggesting a preattentive, spatially parallel process. This process, which is perfect over a spatial window delimited by the anatomical fovea, may form an early input to a multistage analysis of surface color, providing the visual system with information about a rapidly changing world in advance of the generation of a more elaborate and stable perceptual rep resentation.