Abstract
Human conscious perception cannot resolve fast chromatic alternations, for example, at over 25Hz. Previous studies have shown that the temporal limitation of conscious color perception is primarily cortical rather than precortical processes (Vul & MacLeod, 2006; Jiang, Zhou, & He, 2007). Indeed, conjunctions of orientation and color are cortically represented at frame rates much faster than the color fusion rate (Vul & MacLeod, 2006). Here we investigated whether invisible orientation information from fast chromatic flickers has any functional consequences for spatially adjacent or temporally subsequent visible orientation information. In other words, we tested whether the invisible chromatic grating could induce tilt illusion (Exp. 1) and tilt aftereffect (Exp. 2). In experiment 1, observers judged the orientation of a low contrast chromatic grating presented at fixation, surrounded by 30Hz flickering red/green chromatic gratings tilted 15 degrees from the principle orientations. Result shows that the center chromatic grating presented at principle orientations were perceived to be 1~2 degrees tilted away from the invisible surround orientation. In experiment 2, we measured tilt aftereffect following adaptation to invisible red/green flickering chromatic gratings. A low contrast test grating 15 degrees different from the invisible adapting orientation appeared tilted 1.5~2.5 degrees further away from the adapting orientation. These results suggest that the invisible orientation information from fast flickering chromatic gratings has functional significance both spatially and temporally.
Meeting abstract presented at VSS 2013