Kinetic Orbison illusion does not need global shape information

When a dot moves along a square path on concentric circles, the trajectory appears to bend toward the center (kinetic Orbison illusion). However, it is unclear whether the global shape information as a geometrical illusion-the virtual square formed by the dot's trajectory and the concentric circles-is necessary for the illusion. We measured the illusion by limiting the visible area of the stimulus with a circular window. The results showed that the window size did not largely affect the magnitude of illusion. Furthermore, even when the moving dot was presented for 0.4 s, the motion direction was misperceived, corresponding to the kinetic Orbison illusion. The kinetic Orbison illusion may be essentially based on an illusion of motion direction within a spatially and temporally limited area. The continuous observation of the changing perceived motion direction produces a bending impression of the motion path of the dot.