What a coincidence.

Start with a cage containing five monkeys.

 

Inside the cage, you'll see a banana hanging on a string with a set of stairs placed 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, all of the other monkeys are sprayed with cold water.

After a while, another monkey makes an attempt to obtain the banana.  As soon as his foot touches the stairs, all of the other monkeys are sprayed with cold water. It's not long before all of the other monkeys try to prevent any monkey from climbing 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 as he makes his way toward the stairs.  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, then the fifth. Every time the newest monkey takes to the 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. Nevertheless, no monkey ever again approaches the stairs to try for the banana.

 Sources:

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.

Mentioned in:
Galef, B. G., Jr. (1976). Social Transmission of Acquired Behavior: A Discussion of Tradition and Social Learning in Vertebrates. In: Rosenblatt, J.S., Hinde, R.A., Shaw, E. and Beer, C. (eds.), Advances in the study of behavior, Vol. 6, New York: Academic Press, pp. 87-88: