The furrow illusion: peripheral motion becomes aligned with stationary contours.

A spot moved vertically up and down across a background grating that was tilted at 45°. In foveal vision this was seen accurately, but when viewed peripherally the spot's path was perceptually attracted toward the grating orientation, and at large eccentricities (>20°) the spot appeared to move at 45°, parallel to the grating. The intersections between the grating and the moving spot drive this illusion, revealing profound differences between fovea and periphery in processing visual motion.