Look at one specific ring and then shift gaze to another specific ring. Did they start spinning differently? All the rings, in reality, are spinning clockwise. When you look at a ring, your brain can see the rotation of the circles and takes that as the rotating direction for the ring (clockwise). When in your peripheral vision, the rotating rings are read as the rotation of the stripes (spinning counter clockwise and masked by the rotating circles).
Change the speed of the masked stripes:
Change the speed of the rings of circles:
Illusion originally created by Arthur Shapiro. I recreated it using paper.js because I'm fascinated with how the brain perceives. This recreation allows me to play with the parameters.