Stephen L. Macknik in Scientific American:
An entry from The Best Illusion of the Year Contest started off as a representation of the Loch Ness monster, but has grown to become one of the most intriguing, and potentially most important, illusions. The effect stems from a jumping ring: line-segments arranged randomly in an annulus rotate smoothly, and periodically rescramble into a new pattern of randomly arranged line-segments. Bizarrely, the rescrambling appears to viewers as a rapid backward jump in rotation, despite that there is no real motion (or direction of motion) during the rescrambling. Pretty cool.
Mark Wexler of the University of Paris V in France, who discovered the original Loch Ness effect, took third-prize in the contest. He named it the Loch Ness aftereffect after a classic illusion known to ancient Greeks, which Robert Addams later rediscovered in 1834 at the Falls of Foyers (the waterfalls that feed Loch Ness in Scotland). If you stare at the waterfalls for a while, the stationary rocks near the falling water will appear to drift upward. But unlike in the waterfall effect, Wexler’s illusory motion aftereffect is 100 times faster than the inducing movement! So this is not your parent’s waterfall effect: something new is happening.