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Sean F. O'Neil, Megan Tillman, Michael A Webster; The duration of contingent color aftereffects for different directions in color space. Journal of Vision 2010;10(7):393. doi: 10.1167/10.7.393.
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The McCollough effect (ME) is a color aftereffect contingent on orientation. Though studied extensively, the basis for the effect and whether it reflects specialized processes remains poorly understood. ME's are conventionally induced by adapting to gratings that covary in brightness and color (e.g. both bright and red) and then testing on gratings that are achromatic (e.g. bright only). The hue shifts functionally resemble a form of tilt aftereffect within the color-luminance plane (e.g. so that bright bars appear rotated away from bright-red toward bright-green), and are known to have remarkably long persistence (e.g. Vul et al. JOV 2008). We compared the duration of these hue shifts to the shifts in both hue and lightness induced by comparable stimuli in other directions in the color-luminance plane (e.g. to the relative brightness changes induced in isoluminant gratings). Observers adapted to vertical and horizontal gratings with luminance and chromatic (LvsM) contrast paired in or out of phase, and then tracked the aftereffects in achromatic or isoluminant gratings with a matching task. Both types of test gratings show “tilts” away from the color-luminance direction of the adapting grating which are selective for orientation and which may therefore partly reflect common processes like contrast adaptation. However, the marked persistence of the aftereffects in achromatic stimuli suggests that additional processes - which may be specific to luminance edges - contribute to the hue shifts in the conventional ME, and could support a special role of processes like color spreading in the aftereffect (Broerse et al. Vision Research 1999). Differences in aftereffect duration in luminance and chromatic tests also argue against suggestions that the long persistence of the ME results only because the stimuli required to de-adapt are rarely encountered, and suggest instead that the persistence may reflect a special characteristic of the adaptation.
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