The texture filling the rings is either stationary (rings seem to move slowly) or moves in the opposite directions to the rings (rings slide over each other, each spinning CCW as the pair turn CW) or in the same direction as the rings (rings appear to move very fast as a rigid figure-8 .)
The rings appear to slide over one another when the intersections are dark so that they obey Metelli’s transparency rules. They lock together into a rigid trefoil when the intersections are light and look opaque.
Left-hand rotating rings with painted-on spots were parsed as a solid figure of eight. Observers could easily track rigid intersection (lower right graph) (Anstis & Ito, Perception 2011).
Right-hand rotating rings with vertically aligned gaps or spots appeared to slide. Observers could not track sliding intersection where rings cross. Upper right-hand graph shows the noisy pattern of eye movements.
Eye-movement tracked while watching the stimuli.