“They started with a cage containing five monkeys. Inside the cage, they hung a banana on a string with a set of stairs placed under it. Before long, a monkey went to the stairs and started to climb towards the banana. As soon as he started up the stairs, the psychologists sprayed all of the other monkeys with ice cold water. After a while, another monkey made an attempt to obtain the banana. As soon as his foot touched the stairs, all of the other monkeys were sprayed with ice cold water. It’s wasn’t long before all of the other monkeys would physically prevent any monkey from climbing the stairs.
Now, the psychologists shut off the cold water, removed one monkey from the cage and replaced it with a new one. The new monkey saw the banana and started to climb the stairs. To his surprise and horror, all of the other monkeys attacked him. After another attempt and attack, he discovered that if he tried to climb the stairs, he would be assaulted.
Next they removed another of the original five monkeys and replaced it with a new one. The newcomer went to the stairs and was attacked. The previous newcomer took part in the punishment with enthusiasm! Likewise, they replaced a third original monkey with a new one, then a fourth, then the fifth. Every time the newest monkey tried to climb the stairs, he was attacked. The monkeys had no idea why they were not permitted to climb the stairs or why they were beating any monkey that tried. After replacing all the original monkeys, none of the remaining monkeys had ever been sprayed with cold water. Nevertheless, no monkey ever again approached the stairs to try for the banana. Why not? Because as far as they know that’s the way it’s always been around here.”1