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Peng Sun, Charles Chubb, George Sperling; A paradoxical peripheral plaid motion phenomenon. Journal of Vision 2012;12(9):1233. doi: 10.1167/12.9.1233.
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© ARVO (1962-2015); The Authors (2016-present)
The motion direction of a moving sinewave grating is ambiguous. The motion of a plaid, consisting of any two arbitrary translating sinewave gratings is not ambiguous; there is always rigid direction that corresponds to a translation of a snapshot of the plaid. The rigid direction can be determined by the "intersection of constraints" (Adelson & Movshon, Nature1982). In Type 1 plaids, the rigid direction and the vector average direction (of the component sinewaves) are similar; in Type 2 plaids, they differ strongly (Ferrera & Wilson, VisRes1987). In foveal viewing, at high temporal frequencies (12.5+25 Hz) that favor first-order motion perception, the Type 2 plaids investigated here are perceived to move in a vector average direction. At low temporal frequencies, especially with components of equal high contrasts that favor third-order motion perception (feature tracking), the same Type 2 plaids are perceived in the rigid direction (e.g., Liu & Sperling, JOV2008). In the periphery, where acuity is reduced, typically motion perception is biased towards a lower order motion perception system relative to the fovea (Lu & Sperling, P&P1999). In accord with this tendency, 1.5+3 Hz Type 2 plaids that foveally are perceived in the rigid direction (3rd-order), are perceived in the vector average direction (first-order) when viewed 8 deg peripherally. Paradoxically, the same high-contrast (but not low contrast) Type 2 plaids (with 12.5+25 Hz components) that are perceived in a vector average direction foveally, are perceived in the rigid direction peripherally. The computation of perceived motion in the rigid direction at such high temporal frequencies in the periphery when it is not perceived in the fovea is unexplained.
Meeting abstract presented at VSS 2012
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