Color selection, color capture, and afterimage filling-in

R. van Lier, M. Vergeer, and S. Anstis (2009) reported an afterimage that produced different percepts from an inducing stimulus depending on the shape of a subsequent contour. G. Francis (2010) explained this phenomenon with a model where the contour forms a boundary that traps the afterimage color as it spreads across a surface. We conducted a series of additional model simulations and experiments to test the explanation. We first tested the hypothesis that the contour traps the afterimage color by adding additional contours. Model simulations suggest that additional contours could block color from spreading to the middle of the surface. In two experiments, additional contours blocked color spreading when they were at the inducer edges but not when they were drawn away from the inducer edges. In a second set of experiments, we investigated the model prediction that the drawn contour defines the perceived shape of the afterimage. New model simulations predict that variations in the size of the drawn contour force the perceived afterimage to vary accordingly. However, an experimental study revealed that the perceived afterimage size remains the same as the inducing stimulus. The simulation and experimental results both highlight and challenge important characteristics of the model.