Peripheral Drift Illusion

Akiyoshi Kitaoka's "Rotating Snakes" illusion: http://www.ritsumei.ac.jp/~akitaoka/rotsnakee.html

In its usual presentation, the image consists of concentric circles of stepwise luminance gradients with curved edges, which produces a strong illusion of rotation in most observers.

This type of illusion, often called a peripheral drift illusion, was thought to occur due to slow drifting eye movements but a new study suggests that it is more likely to be explained by rapid but tiny eye movements ("transient oculomotor events") called saccades.