The hundredth monkey effect is an esoteric idea claiming a new behavior is spread rapidly by unexplained means from one group to all related groups once a critical number of members of one group exhibit the new behavior.

In the 1950s, a group of Japanese macaque monkeys on the island of Koshima began washing their sweet potatoes before eating them. This behavior spread through the population until, at some point, it was said that a critical mass was reached — the so-called 100th monkey.

Suddenly, monkeys on other islands, with no direct contact with the original group, began to exhibit the same behavior.

This phenomenon was later coined the “100th Monkey Effect” and is often used as an example of a sudden, widespread shift in consciousness or collective learning. While many embrace the concept as a powerful symbol of change, others dismiss it as a mere anecdote, lacking scientific rigor.

Context.org has also reported there was no mention of the group passing a critical threshold that would impart the idea to the entire troop. The older monkeys remained steadfastly ignorant of the new behavior. Likewise, there was no mention of widespread sweet potato washing in other monkey troops. 

‘I think there are other simpler explanations’

There was mention of occasional sweet potato washing by individual monkeys in other troops, but I think there are other simpler explanations for such occurrences. If there was an Imo in one troop, there could be other Imo-like monkeys in other troops.

I think the story of the Japanese monkeys is a good example of the propagation of a paradigm shift, as in Thomas Kuhn’s The Structure of Scientific Revolutions. The truly innovative points of view tend to come from those on the edge between youth and adulthood. 

The older generation continues to cling to the worldview they grew up with. The new idea does not become universal until the older generation withdraws from power, and a younger generation matures with the new point of view.

It is also an example of the way that simple innovations can lead to extensive cultural change. By using the water in connection with their food, the Koshima monkeys began to exploit the sea as a resource in their environment. 

Sweet potato washing led to wheat washing, and then to bathing behavior swimming, and the utilisation of sea plants and animals for food.

 "Therefore, provisioned monkeys suffered changes in their attitude and value system and were given foundations on which pre-cultural phenomena developed." (M Kawai, Primates, Vol 6, #1, 1965).

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