Displacement of the path of perceived movement by intersection with static contours

Observation of a moving dot gives rise to a perceived movement path, which has properties similar to those of real contours. If the dot crosses a line inclined to a horizontal direction of movement, it appears to undergo a vertical displacement. This displacement was found to be greatest for a line orientation of around 15° with respect to the movement. At other relative orientations, the size of the perceived displacement varied in the same manner as the perceived expansion of angles formed by intersection between static contours. Movement path distortions were measured with background fields like those that produce the Hering and Zöllner illusions with continuous lines. Illusory displacements of perceived movement were found to be equivalent to the static forms. The subjective contour formed by observation of movement can therefore give rise to illusions similar to those obtained with real lines.