Chopsticks Illusion

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 stimuli are the same except for the small white 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.

Headshot of Hiro ItoBelow: 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).
07 PortholeChop2

The video above may not display in your browser. If this is the case, you may view it by clicking it, which will open it in a new tab. It shows the chopstick illusion superimposed on text so that the moving sticks appear to be “portholes” into text hidden behind the white backgroun.