There has been a fable making the rounds since the 1990s about a group of monkeys. In the fable, five monkeys were placed in a cage, with a batch of bananas hanging from the ceiling (beyond the reach of the monkeys) and a ladder right underneath it.
It only took a few seconds for one of the monkeys to begin climbing to grab the bananas. As it did, a researcher sprayed it with a stream of cold water. Soon, each of the monkeys learned not to climb the ladder. Furthermore, if any of them started to, the others would hold them back forcefully.