Changes in color appearance caused by perceptual grouping.

How is chromatic induction affected by perceptual grouping? Chromatic induction has been studied extensively, as has grouping, but only a small number of experiments have connected them. Even fewer reports go beyond weakly controlled qualitative observations. We report here a new and substantial color shift caused by perceptual grouping: a shift in appearance due to chromatic induction in one part of the visual field occurs also in a separate region that belongs to the same group. The color appearance of a test square within various surrounds was measured by asymmetric matching. The test square was at the center of an "hourglass" structure formed by other elements in the surround. The test shifted in color appearance toward the appearance of these other elements, whose color was affected by local chromatic induction. Control experiments ruled out as explanations (1) direct chromatic induction from the other elements into the test area, and (2) the influence of background light occluded by introducing the elements forming the hourglass.