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Sae Kaneko, Ikuya Murakami; Effective ranges of shorter durations yielding greater simultaneous contrast of brightness and color. Journal of Vision 2012;12(9):1216. doi: 10.1167/12.9.1216.
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Perceived brightness and color can be affected by surrounding light. We previously demonstrated (Kaneko & Murakami, VSS, 2011) that these illusions of simultaneous brightness contrast and color contrast are both greatly enhanced when the stimulus is flashed briefly (for a single video frame), compared to the illusions seen in longer-lasting stimuli. We argued that different processes were involved in the illusions depending on stimulus duration. In the present study, we systematically varied the stimulus duration and examined the temporal dynamics of these illusions to see how quickly the switch from one process to another occurs. We used the method of adjustment to measure the perceived brightness or color of a test disk (radius 0.5 deg) positioned at the center of a larger annulus (radius 8.25/5 deg) of various luminance or color. The colors of the annulus used in this color matching experiment were constrained along the cardinal axes on the equiluminant plane in DKL color space. The luminance/color of the test was the same as that of the background and was kept constant throughout session whereas the duration of the larger annulus was varied from 10 to 640 ms. Subjects were requested to adjust the luminance/color of a comparison disk surrounded by luminance noise to match the brightness/color of the test disk. The illusion strength showed a sharp drop with increasing stimulus duration and rapidly reached a steady level. This temporal profile was found in both brightness matching and color matching results. We fitted an exponential decay function to each profile and obtained time constants for individual data. The time constants in the brightness matching data were longer than those in the color matching data. This suggests that although in principle both illusions show enhancement at short durations, the underlying mechanisms that bring the enhancement are not necessarily the same.
Meeting abstract presented at VSS 2012
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