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Hyung-Chul O. Li, Eun-Soo Kim; The effect of a reference on eye-movement-induced distortions of motion-defined shapes. Journal of Vision 2002;2(7):304. doi: 10.1167/2.7.304.
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© ARVO (1962-2015); The Authors (2016-present)
In ARVO 2001, we showed that the perceived shape of a spatiotemporally-defined 2D object reflected the content of the retinal rather than physical image during pursuit eye movement (i.e., a rectangle appeared as a parallelogram). Would the presence of reference patches surrounding the target rectangle improve shape perception? If shape perception were to utilize the relative position information of the references, the perceived shape should be a rectangle rather than a parallelogram. We manipulated both the contrast of the reference patches as well as their distance from the target. Subjects tracked a dot moving horizontally over a rectangle which was defined by the occlusion of a vertically moving bar, and they reported the perceived shape of the target by adjusting a comparison shape. In a separate session, subjects also reported the position of the top/bottom side of the target relative to the references. Both shape distortions and positional biases in the direction of pursuit were observed even with the reference patches. However, the amount of shape distortion and positional error decreased as the reference patches increased in contrast and became closer to the target. Interestingly, when there was no gap between target and reference, shape distortions were observed even though there were no localization errors. These results imply that the visual system uses object-relative information to improve shape perception, and that the shapes of spatiotemporally defined objects are processed independently of the position of the local elements comprising the objects.
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