A 30-second film shows six people playing basketball, three in white shirts and three in black. Volunteers are asked to count the number of times the white shirt team pass the ball. At the end of the film, they are asked if they saw anything unusual. Most do not. The unusual thing is: halfway through the film, a man wearing a gorilla suit walks through the players, beats his chest to the camera, then walks off.
When shown the film again, people are utterly amazed to see this, to the extent that they often believe a different film has been substituted for the original one. Their focus on one task has blinded them to a truth.
The film illustrates a simple fact--that if we are only looking for one thing, we do not usually see anything different. This forms the basis of Professor Richard Wiseman's new book:
Did You Spot The Gorilla:
How to Recognise Hidden Opportunities
R Wiseman
Arrow Books (London)
ISBN 0-09-946643-0
The point at which people finally see the unexpected is what he calls a 'gorilla moment'.