The 100th Monkey Effect

By: Jaden Li

Have you ever seen some truly weird behavior that you thought was specific to your own school? Then, by talking to your friends from other schools, you find out that they experience the exact same thing? Whether it’s silly bands or Pokémon cards, a lot of us had very similar childhoods. Why is that?

The hundredth monkey effect might be able to explain it. It’s a hypothetical phenomenon in which a new behavior or idea is spread rapidly by inexplicable means from one group to all related groups once a certain threshold of members of one group exhibit the new behavior or acknowledge the new idea. So maybe your friend group has a certain speech pattern. Once it has spread to everyone in your group, it then spreads to the rest of the school without reason.

The phenomenon was first popularized in the 1970s by Lyall Watson after she documented the findings of Japanese primatologists in the 1950s. The scientists provided Japanese monkeys on different islands with various foods like sweet potatoes and wheat. A sudden unexpected result was new innovative behavior from some of the monkeys. They learned to wash the sweet potatoes. The behavior began to pop up on nearby islands. Watson believed a group consciousness developed among them. She concluded that once a certain threshold — the hundredth monkey — was hit, the behavior spread to nearby islands.

However, Watson’s conclusions aren’t cut and dry. Many scientists have reevaluated the findings of the Japanese scientists and found no hundredth monkey effect exists. Ron Amundson was one of the main debunkers of this phenomenon. When he revisited the data, no jump was observed in monkeys that washed their sweet potatoes. Other islands didn’t experience a huge increase but had small starts that never spread as completely. One spread to other islands occurred through one monkey swimming to a nearby island as a new home. Now, the phenomenon has been discredited for using too many secondary, tertiary, and post-tertiary sources to back up its claims. Whether or not you want to believe in the hundredth monkey effect, it could be one reason why everyone seems to have the same childhood.