The Hundredth Monkey Effect

In the year 1980, Lyall Watson was the first biologist to propose the theory of “The Hundredth Monkey Effect”, in his book, ‘lifetide’. He mentioned about a phenomenon that the Japanese primatologist discovered while studying the Macaque monkey in the wild in the 1990s.

The Japanese snow monkey, Macaca fuscata, was kept under observation for over 30 years. In the year 1952, on the island of Koshima, a group of scientist provided a group of monkeys with sweet potatoes covered in sand. The monkeys liked the taste of the sweet potatoes, but found the dirt unpleasant.

An 18-month-old female monkey found a solution. She washed the potatoes in a nearby stream and shared her discovery with her mother. She also taught it to her playmates who further showed it to their mothers.

This cultural discovery was eventually being picked up many monkeys. At least such was the observation gain by the scientist

Between 1952 and 1958, almost all the young monkeys had learned to wash the sandy sweet potatoes. Only the adults who imitated their children learned this social improvement. Other adults continued to eat dirty sweet potatoes.

Then a startling phenomenon was observed.

In 1958, a certain number of Koshima monkeys were washing sweet potatoes — the exact number is not known. The assumption was that if at the dawn of a particular day, 99 monkeys knew about washing the potatoes, then by the dusk of the same day 100 monkeys knew.

By that evening almost everyone in the tribe was washing sweet potatoes before eating them. The added energy of this hundredth monkey somehow created an ideological breakthrough!

Another exemplary fact observed by the scientist was the journey of this knowledge overseas. Colonies of monkeys on other islands and the mainland troop of monkeys at Takasakiyama began washing their sweet potatoes too!

A hypothesis were then drawn- when a certain critical number achieves an awareness, this new awareness can be communicated through mental energy.

Although the exact number may vary, the Hundredth Monkey Phenomenon implies that when only a limited number of people know of a new way, it may remain the conscious property of these people.

But here lies a point over which even a single addition of a new awareness can significantly strengthen the field of awareness to that extent that it is picked up by almost everyone within a short span of time!

Quote about Positive Thinking

Source: The story is an excerpt from the book The Hundredth Monkey by Ken Keyes, Jr., while demonstrating the power of positive thinking. This excerpt was originally featured on

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