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Andrew Coia, Steven Shevell; Chromatic Induction and the Flash Lag Effect. Journal of Vision 2017;17(10):654. doi: 10.1167/17.10.654.
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The flash lag effect demonstrates that a flashed object is perceived to lag behind a moving one even when they are identical at the moment of the flash. Anstis (2007), using a motion illusion, showed that the flash lag depends on physical rather than perceived motion. A variant of the flash lag effect occurs with color: the color of a flashed object appears to lag behind the color of another object continuously changing in chromaticity. The current study tested whether color flash lag judgments are based on perceived color or physical chromaticity. METHODS: Chromatic induction was employed to make a test ring, which appeared red on a neutral grey surround, appear orange when surrounded by one chromatic pattern or pink when surrounded by another pattern (patterned surrounds after Monnier and Shevell, 2003). Matching experiments compared test rings within patterned surrounds (induction) to rings within a uniform neutral surround (no induction). Observers adjusted the chromaticity of the flashed ring to match the color of the changing ring. The changing-ring's chromaticity could go from either orange→red→pink, or pink→red→orange. RESULTS: Initially, both test rings were on uniform neutral surrounds. These baseline measurements confirmed the color flash lag effect, and were compared to conditions with either the changing or flashed ring within a patterned surround. When only the changing ring had a patterned surround, observers shifted the color of the flashed ring to account for chromatic induction from the surround. Similarly, when only the flashed ring had a patterned surround, observers' matches also were shifted by the surround. CONCLUSION: The flash lag effect for color is based on the color perceived, not the physical chromaticity of the stimulus. This differs from the motion flash-lag effect (Anstis, 2007), indicating that flash lags for motion and for color are mediated by different neural mechanisms.
Meeting abstract presented at VSS 2017
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