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Lanya Tianhao Cai, Benjamin Backus; Global motion perception is faster but less accurate with dark random-dot kinematograms. Journal of Vision 2018;18(10):295. doi: https://doi.org/10.1167/18.10.295.
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Primate vision exhibits a "light-dark asymmetry" originating from ON and OFF channels in the retina. Neurophysiology and psychophysics show a processing speed advantage for darks (Komban et al. 2011 J Neurosci). We looked for a corresponding "dark benefit" in global motion perception. Performance of global motion perception in random-dot kinematograms (RDKs) can be assessed in terms of reaction time and accuracy. We hypothesized that a dark benefit in early vision could lead to better efficiency for dark dots as compared to light dots, in the form of a shorter reaction time or a higher accuracy, or both. We measured speed-accuracy trade-off functions (SATF) in 3 contrast polarity conditions of RDKs: white dots on a gray background (W/G), black dots on a gray background (B/G), and gray dots on a black background (G/B), and expected to see a dark benefit with black dots on a gray background. Viewing of signal and noise dots was monocular or segregated, to test whether binocularity interacts with dot polarity. Indeed, we found a slightly shorter latency in the SATF's deviation from chance for black dots. However, this dark benefit was not general: performance was not better for black dots. These findings suggest that the processing speed advantage for darks is preserved at the level of global motion perception, but that response properties of the OFF pathway limit that pathway's spatiotemporal summation window in early vision, which compromises motion discrimination performance.
Meeting abstract presented at VSS 2018
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