Start with a cage containing five monkeys. Inside the cage,
hang a banana on a string and place a set of stairs under it. Before long, a
monkey will go to the stairs and start to climb towards the banana. As soon as
he touches the stairs, spray all of the monkeys with cold water.
After a while, another monkey makes an attempt with the same result - all the monkeys are sprayed with cold water. Pretty soon, when another monkey tries to climb the stairs, the other monkeys will try to prevent it.
Now, turn off 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.
Again, replace a third original monkey with a new one. The new one makes it to the stairs and is attacked as well. Two of the four monkeys that beat 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 the fourth and fifth original monkeys, all the monkeys that have been sprayed with cold water have been replaced. Nevertheless, no monkey ever again approaches the stairs. Why not?
Because as far as they know that's the way it's always been around here.
Original Study: Stephenson, G. R. (1967). Cultural acquisition of a specific learned response among rhesus monkeys. In: Starek, D., Schneider, R., and Kuhn, H. J. (eds.), Progress in Primatology, Stuttgart: Fischer, pp. 279-288.