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Paul Hibbard, Peter Scarfe, Michelle Robertson, Stacey Windeatt; Motion adaptation affects perceived shape. Journal of Vision 2010;10(7):831. doi: 10.1167/10.7.831.
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Adaptation to a moving image causes subsequently presented stationary stimuli to appear to move in the opposite direction. Motion adaptation also affects the perceived location and size of stimuli. After adaptation to motion in one direction, the positions of subsequently presented static stimuli appear shifted in a direction opposite to that of the adapting stimulus (Snowden (1998), Current Biology 8, 1343-1345; Nishida & Johnston, (1999), Nature, 397, 610-612). Similarly, adaptation to expanding and contracting motion has been shown to alter the perceived size of objects consistent with the direction of the motion after-effect (Whitaker, McGraw & Pearson (1999), Vision Research, 39, 2999-3009). Here we demonstrate that adaptation to motion also affects the perceived shape of stimuli. Observers were presented with rectangular stimuli, and asked to determine whether, in comparison with a square, they appeared stretched or squashed in the vertical direction. Judgements were made in three conditions (i) a baseline, with no adaptation (ii) after adaptation to a vertically expanding pattern of motion, during which dots above the horizontal midline moved upwards, and dots below the horizontal midline moved downwards, and (iii) after adaptation to a vertically compressing pattern of motion, during which dots above the horizontal midline moved downwards, and dots below the horizontal midline moved upwards. In each case, the point of subjective equality (the apparently square rectangle) was calculated to determine whether perceived shape was affected by motion adaptation. Adaptation to a vertically compressing motion caused subsequently presented rectangles to appear stretched in the vertical direction; adaptation to expanding motion had no effect on perceived shape. We conclude that, in addition to its effects on apparent motion, position and size, motion adaptation can also affect perceived shape.
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