Each chopstick moves along a clockwise (CW) circular path. their intersection also appears to move CW, although it really moves CCW. Conclusion: The CW motion of the tips propagates along the lines to the central intersection. (To avoid interactions, look at each display in turn while covering the others with your hand.)
Similarly, the two black ring stiuli are the same except fo the small whute gaps. Left: When the gaps float, always lying at ‘6 & 12 o’clock’, one perceives two rings circling each other. Right: When the gaps rotate with the rings, one perceives a single rotating figure-8. So local gaps control the global percept.
On the left: Try to track the central intersection of the chopsticks, or the X-junction where the rings intersect. You cannot! So pursuit eye movements are not simple dumb clockwork servos, but are controlled by top-down object parsing.
Below: HIRO ITO recorded eye movements tracking the chopstick stimulus with and without a surrounding frame.
With the frame present, CW motion is seen correctly and eye movements (red trace) are accurate. Without the frame, the intersection appears to move CCW and eyes can no longer track it properly. Tracking errors are 10x greater without the frame! (Blue spot was not present in original stimulus).