Chopstick Illusion

On the left, the two chopsticks appear to rotate counterclockwise in counterphase. On the right, a circular aperture isolates the "+" pattern at the cross-over. Note that the "+" actually rotates in the clockwise direction (Anstis, 1990). Why is this motion signal disregarded by the visual system? One of the reasons could be that the motion of the chopstick terminators prevails, as in the barberpole effect. Another reason may have to do with figure/ground segregation, as in the sliding effect.

created by Fauzia Mosca and Nicola Bruno