Abstract
VanHorn and Francis (VSS 2007 & 2008) described a switch color afterimage, where, the colors in an inducing image grating switch positions in the afterimage. For example, a blue and black bar inducer grating produces a black and blue bar grating afterimage. Similar reports of color contrast afterimages have previously been reported (Anstis, Rogers, and Henry, 1978; Ferree & Rand, 1912; King & Wertheimer, 1963; Poppel, 1986; Shively, 1973), but have received little systematic investigation. In this study we varied the number of bars in the inducing grating to observe the transition between negative color afterimages and switch color afterimages. Observers reported perceived colors with a color matching technique. We find that an individual blue bar stimulus and an individual black bar stimulus produce negative afterimages (yellow and white afterimages respectively). As flanking black and blue bars are alternately added to the blue bar stimulus (transitioning it to a blue and black bar grating) the afterimage of the blue bar darkens and is reported as having little to no yellow. As flanking blue and black bars are alternately added to the black bar stimulus (transitioning it to a black and blue bar grating) the afterimage of the black bar is reported as blue. The transition from a negative afterimage to a switch afterimage is almost complete after the addition of one flanking bar on each side of the individual bar stimulus.