Courtesy of Boing Boing:
Click on the link below and look at the spinning dancer image. Stare long enough and she’ll change directions. How do I know it is not a trick? Because after a few minutes I could figure out ways to trick my brain into getting her to change directions and could do it at will.
http://www.maniacworld.com/Spinning-Silhouette-Optical-Illusion.html
