5 monkeys were put in a cage. A ladder was placed in the middle of the cage, with a bunch of bananas located at the top of it.
After some time, one of the monkeys would attempt to climb the ladder to get to the bananas. After all, it’s free food!
However, once this happens, the other 4 monkeys were sprayed with cold water. Basically, each time a monkey climbed up the ladder, the other four were sprayed with cold water.
After some time, when one of the monkeys attempted to ascend the ladder, the other 4 monkeys would give him a good bashing to prevent him from climbing it. Why? Well, they wanted to avoid being sprayed with the cold water, presumably!
And this phenomenon went on even after the spraying of cold water was no longer continued.
Now, one of the 5 monkeys was removed from the cage, and replaced with a new one, one who had never witnessed the cold water spraying. He saw the bananas and, just as what any sane monkey would do, he attempted to climb the ladder to get to them.
Unfortunately, the other 4 monkeys gave him a right ol’ bashing, preventing him from getting to the bananas. He tried again, but got attacked once more, and after a few attempts, he wised up and gave up on trying to get hold of the bananas.
Another one of the remaining 4 monkeys from the original group of 5 was removed from the cage, and again replaced with a new one, one who had never seen the cold water spraying. The pattern repeated, with the new monkey attempting to climb the ladder, and the other monkeys giving him a beating. After a while, this 2nd new monkey, too, gave up. Interestingly, the 1st new monkey, although himself never having been sprayed with cold water, also took part in the attack with enthusiasm!
The pattern was repeated once again - 3rd monkey removed, and replaced with 3rd new monkey; 4th monkey removed, and replaced with 4th new monkey; final monkey removed, and replaced with 5th new monkey. And the same phenomenon continued to take place.
By the time all 5 of the original group of monkeys had been replaced, none of the 5 new monkeys which were in the cage had been sprayed with cold water. Yet, when the newest monkey attempted to climb the ladder, the other 4 would still proceed to batter him. Therefore, a kind of “equilibrium situation” was reached, whereby no monkey ever dared to ascend the ladder and get the bananas, even if the cold water had been put away and never used again.
Why would the monkeys do that? None of them had ever even been sprayed with cold water!