Five monkeys in a room. In the middle of the room is a ladder, leading to a bunch of bananas hanging from a hook on the ceiling: Each time a monkey tries to climb the ladder, all the monkeys


 are sprayed with cold water. Soon, whenever a

monkey attempts to climb the ladder, all the
other monkeys, not wanting to be sprayed, set
upon him and beat him up.
Eventually, no monkey dares to try climbing
the ladder. One of the original monkeys is then
removed, and a new one is introduced to the
room. Spotting the bananas, he naively tries to
climb the ladder. The other monkeys attack him.
After another attempt and attack, he knows
that if he tries to climb the ladder, he will be
assaulted.
Next, another of the original five monkeys is
removed, and a new one is introduced to the
room. The newcomer goes to the ladder and is
attacked. The previous newcomer takes part in
the punishment with enthusiasm.
Again, a third original monkey is removed and
a new one introduced. The new one makes it to
the ladder and is attacked as well. Two of the
four monkeys that beat him have no idea why
they were not permitted to climb the ladder or
why they are participating in the beating of the
newcomer.
After the fourth and fifth original monkeys are
replaced, all the monkeys that are beating the
newcomers have been sprayed with cold water.
Nevertheless, no monkey ever again approaches
the ladder.