Hues of Color Afterimages

Abstract

We studied the relationship between color afterimages and complementary colors. The hues of afterimages of 24 inducer hues, uniformly distributed over the RGB color circle, were measured by an iterative method of adjustment. The judgment of equality of hue of the afterimage and a synthesized patch was effectively judged at the moment immediately after the switch-off of the inducer, when the synthesized patch went through any number of iterative adjustments. The two patches-both phenomenally present, but only one optically presented-appeared to the left and right of a fixation mark that was fixated throughout the whole procedure. Thus, both patches were present in eccentric vision. The hues of afterimages were found to be quite different from the hue of the complementary of the inducer. Almost one half of the color circle (orange to chartreuse) leads to afterimage hues in a narrow region of purples. This implies that color circles based on diametrically opposed inducer-afterimage hues are necessarily inconsistent. Yet, perhaps surprisingly, the relation between primary and afterimage hues is still approximately an involution (they are reciprocally related).

The Mechanisms Underlying Colour Afterimages

“…Our results replicate, extend, and explain observations of three clusters that contradict a cone-opponent origin 14 .…”

“…Research and textbooks have missed the fact that the adaptation of different perceptual mechanisms makes fundamentally different predictions about the hue and saturation of afterimages [2][3][4][5][6]14,26 . These predictions can be tested empirically, using experimental paradigms that allow for measuring the exact colours perceived in afterimages.…”

“…Figure 1.c). 16 Unlike what current textbooks suggest [3][4][5]7,8 , colour afterimages are neither determined by cone-nor by Hering-like colour opponency. A cursory look at afterimages may be misleading because afterimages resemble cone-opponency at a very coarse level 29 .…”

“…Most state-of-the-art research assumes that afterimages correspond to the colour predicted by cone-opponent mechanisms at the second stage of colour processing 2,5,13,14,18 , but again others found contradictory results [15][16][17] . Evidence for this idea has been provided by tasks showing the successful nulling of afterimages in cone-opponent space 13 .…”

“…The classical explanation suggested afterimages are due to cone-bleaching at the first stage of colour processing 7 , but others found contradictory results 8,9 . Most state-of-the-art research attributes afterimages to the cone-opponent mechanisms at the second stage of colour processing 2,5,10-12 , but again others found contradictory results [13][14][15] . Still others, claim that afterimages occur through adaptation of higher, cortical mechanisms that involve shape and object recognition [16][17][18] , binocular integration 19,20 and/or colour constancy 21 , contradicting classical evidence for a retinal origin 22,23 .…”