“Four monkeys were placed in a room that had a tall pole in the center.  Suspended from the top of that pole was a bunch of bananas.  One of the hungry monkeys started climbing the pole to get something to eat, but just as she reached out to grab a banana, she was sprayed with a torrent of cold water from a hose.  Squealing, she scampered back down the pole and abandoned her attempt to feed herself.  Each of the other three monkeys made similar attempts and each one was drenched with cold water.  After making several attempts, they all finally gave up.

The researchers then removed the water hose and one of the monkeys from the room and replaced her with a new monkey.  As the newcomer began to climb the pole, the other three grabbed her and pulled her down to the ground.  After trying to climb the pole several times and being dragged down by the others, she finally gave up and never attempted to climb the pole again.

The researchers continued to replace the original monkeys, one by one, and each time a new monkey was brought in the others would drag her down before she could reach the bananas.  In a short time, the room was filled with four monkeys who had never received a cold hosing.  None of them would climb the pole or allow other monkeys to climb the pole, and not one of them knew why.”