(Left) Isia Leviant’s Enigma. Most viewers say the purple rings appear to fill with rapid illusory motion. (Right) A simplified version that the researchers used in the study. Most viewers report illusory motion lengthwise along the gray stripe.
When viewing the famous optical illusion painting Enigma by Isia Leviant, many people claim to see motion within the colored circles moving against the black and white striped background. Although this optical illusion has been known for a long time, its physiological origins are still unknown.