This also has elements of the "5 monkey experiment" in conditioning.

5 monkeys are placed in a room with a ladder in the center, which has a banana at the top. However, as any monkey begins to climb the ladder, the rest are sprayed with water. Pretty soon, the monkeys are actively preventing each other from climbing the ladder, as none of them wants to be sprayed with water. After enough time has passed, the water spraying is ended- but the monkeys do not learn this, as they refuse to allow any monkey to climb the ladder and find out. They remember being sprayed all too well, and do not want to endure it again.

Soon, one of the monkeys is taken out and replaced with a new monkey. This one sees the banana and begins to climb- but the other monkeys, feeling they have seen this before, jump on the new monkey and drag it down. The new monkey quickly learns: anyone who tries to climb the ladder is pulled down. It learns not to climb, and to pull down any others who do. But it does not know why- this is simply the way things are.

This process is repeated until, one by one, all the original monkeys have been replaced. The room is now populated by monkeys who will refuse to climb the ladder, and will not allow any others to climb. And not one of them knows why.