The video above shows the top winner in the annual Illusion of the Year competition. It's called the Dual Axis illusion by Frank Force. Is this shape spinning vertically or horizontally? You can't tell, because it's a 2D image, but your brain makes it seem one or the other, until visual cues help you change the orientation. Another of the finalists, Bodiject Fingers by Kenri Kodaka, shows us how seeing one's fingers as disembodied from our hands makes them seem like separate foreign objects.
All it takes is a mirror, and some students to freak out. See all the top ten finalists here. -via reddit