Abstract
Visual motion causes a number of illusions in which object positions are spatially mislocalized. Moving objects themselves are also subject to spatial distortions (e.g. Ehrenstein, 1925; Anstis et al., 1999; Zanker et al., 2001). In the present study we show that moving diamond shapes or isosceles triangles composed of dots at the vertices appeared asymmetrically distorted, with the leading dot seen extended in the direction of motion and the trailing dot compressed toward the center of the shape. These distortions are independent of contrast polarity and differential contrasts of dots composing the figure, and scale proportionally to the object's speed. Explicitly manipulating attention to the leading or trailing part of the shape changed the spatial distortions. When participants were required to respond to the orientation of lines superimposed on the leading dot at random time points during the motion, while keeping steady fixation, they perceived the shapes more accurately. Attention to the trailing dot, however, increased the shape distortions. We discuss several possible explanations of the these findings, including motion extrapolation specific to leading parts of an object, motion deblurring specific to trailing parts, and spatiotemporally specific attentional repulsion due to the locus of attentional tracking lagging behind the moving object.