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When the black and white bars switch places, on a dark surround (left) the white bar appears to jump, but on a light surround (right) the black bar appears to jump. The bar with the higher contrast wins out. The mid-grey at which the motions balance is the arithmetic (not geometric) mean of the black & white, suggesting linear, not logarithmic processing of luminance. (Anstis & Mather, Perception 1986). |
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Ambiguous apparent motion. The two spots move either vertically or horizontally. Can you control the direction by willpower? |
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Proximity: Motion is seen between nearest neighbors, horizontally on the left, vertically on the right. Shorter motion paths win out. |
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Visual inertia drives ambiguous apparent motion. Each spot appears to follow a horizontal path, not jumping up or down halfway across. Straight motion paths are preferred to going round corners. |
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The ambiguous motions all remain locked in step -- all move horizontally, or all move vertically |