In 1967, a group of scientists designed an experiment where five monkeys were put in one cage with a ladder in the middle and a banana suspended over it. When a monkey tried to climb the ladder to reach the banana, it was hosed down with ice cold water to discourage it. However, at the same time the four other monkeys were sprayed as well. This was repeated until the monkeys were conditioned not to climb the ladder as it meant being blasted by cold water. Interestingly, even when the reward was tempting enough for a monkey to brace the cold water and climb the ladder, the monkey was swiftly taken down by the other monkeys – fearing the cold water – and was punished by a beating. This further discouraged the monkeys from climbing the ladder even when the researchers stopped spraying the monkeys with water.
The researchers then substituted one of the original monkeys with a new monkey who had not been in the cage before. This new monkey immediately noticed the banana and started to climb the ladder. The other monkeys saw this and responded with rage, enforcing their unspoken “rule” of never climbing the ladder. The new monkey quickly learned that climbing the ladder was a bad thing.
The researchers substituted another original monkey for a new monkey and the same thing happened. They repeated this until all monkeys were replaced.
When they substituted the last monkey in (number 10), the cage was already filled with “new” monkeys who had never been hosed before, but nonetheless knew not to climb the ladder. When the monkey was punished for climbing the ladder, it gave an expression that seemed to question why he was being punished. The other monkeys did not know why; none of them had been punished with cold water and only knew that the other monkeys would beat him up. Even though none of them knew why the punishment was required, they dished it out regardless. The rule had been engrained into the mob, with each monkey following it without any logical reason.