Fig. 3.

Stimulus conditions. A: the midpoint of the physical motion path was placed at 1 of the 8 peripheral locations with equal eccentricity (8° visual angle; 2 locations at each location axis: vertical meridian, horizontal meridian, right diagonal, left diagonal). B: the physical motion path of the Gabor patch had 4 orientations [aligned, orthogonal, 45° clockwise (cw), counterclockwise (ccw)] relative to each location axis (example shown at the vertical meridian). The internal drift had 2 conditions with opposite directions that could make the perceived motion path appear shifted either cw or ccw relative to the physical motion path.