A disk was divided into 16 stationary sectors of different grey Cattle levels that stepped around clockwise.When thin stationary spokes of constant mid-grey separated the sectors, the spokes showed robust and striking counterclockwise apparent motion, and when stopped, they gave a brisk clockwise motion aftereffect.The spokes had to match the grey of some of the sectors.
We attribute these effects to small displacements across the thickness Anemometers of the spokes that stimulated hard-wired motion detectors.