Start a cage containing 5 monkeys. Inside the cage, hang a banana on a string and place a set of stairs under it. Before long, one of the monkeys will go to the stairs and start to climb towards the banana. As soon as he touches the stairs, all of the monkeys are sprayed with cold water.
After a while, another monkey makes an attempt with the same result, that all the monkeys are sprayed with cold water. Pretty soon, none of the monkeys will try to climb the stairs. Now, put away the cold water. Remove one monkey from the cage and replace it with a new one. The new monkey sees the banana and wants to climb the stairs. To his surprise and horror, all of the other monkeys attack him. After another attempt and attack, he knows that if he tries to climb the stairs, he will be assaulted.
Next, remove another of the original five monkeys and replace it with a new one. The newcomer goes to the stairs and is attacked. The previous newcomer takes part in the punishment with enthusiasm! Likewise, replace a third original monkey with a new one, then a fourth, and then the fifth. Every time the newest monkey takes tot he stairs, he is attacked. Most of the monkeys that are beating him have no idea why they were not permitted to climb the stairs or why they are participating in the beating of the newest monkey.
After replacing all the original monkeys, none of the remaining monkeys have ever been sprayed with cold water. Nonetheless, no monkey ever again approaches the stairs to try for the banana. Why not?
It's because as far as they know, that's the way it's always been done around here.