How Blind Are We?; 105 Mind-Bending Illusions; Special Editions; by Vilayanur S. Ramachandran and Diane Rogers-Ramachandran; 2 Page(s)

Pretend you are a member of an audience watching several people dribbling and passing a basketball among themselves. Your job is to count the number of times each player makes a pass to another person during a 60-second period. You find you need to concentrate, because the ball is flying so quickly. Then, someone dressed in a gorilla suit ambles across the floor (left). He walks through the players, turns to face the viewers, thumps his chest and leaves. Astonishingly, as Daniel J. Simons, now at the University of Illinois, and Christopher F. Chabris of Harvard University learned when they conducted this study, 50 percent of people fail to notice the gorilla.

We think of our eyes as video cameras that make a flawless recording of the world around us, but this demonstration shows how little information we actually take in at a glance.