Abstract
Simons et al. (2006, JoV) described a visual fading effect where a low-pass filtered complex scene faded to a uniform luminance and hue when viewed with steady fixation. The extent and speed of fading was enhanced when transient dots were superimposed on the image. New simulations of Grossberg's FACADE model of visual perception demonstrate that the model is able to account for many of the properties of this kind of visual fading. In the model visual percepts are defined by filled-in colors that are trapped by appropriate boundary signals. In complex scenes these boundary signals form boundary web groupings that block colors from spreading and interacting. With low-passed images and steady fixation local adaptation of orientation-sensitive cells that generate boundaries gradually weaken thereby freeing colors to spread and fade. The same kind of orientation-based adaptation produces an orientation after-response at the offset of transient dots. These orientation after-responses are orthogonal to the boundaries that surround the circles, and as result they interfere with boundary grouping mechanisms for other parts of the scene. By weakening the boundary web groupings, this interference accelerates color spreading and perceived fading. Global decreases in contrast can cause a similar type of orientation after-response for contours across the scene and also accelerate perceived fading. Overall, the model simulations match many of the empirical findings.