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Senior Researcher Comments on the Hundredth Monkey Phenomenon in Japan


Markus Pössel & Ron Amundson

Skeptical Inquirer Volume 20.3, May / June 1996

The pseudoscientific myth of the Hundredth Monkey Phenomenon (HMP) was devised by Lyall Watson in 1979 and has been written about in the Skeptical Inquirer.1

Like many pseudoscientific myths, the HMP was an elaboration of genuine scientific research.

Recent contact with a researcher close to the monkey research provides more insight into the possible origin of this myth.

The story went like this: Primatologists in Japan had discovered and carefully documented the spread, from monkey to monkey, of a particular feeding behavior within a group of macaques (rhesus monkeys) on Koshima Islet. The primatologists supplied a group of free-range macaques with sweet potatoes. One young macaque discovered that washing the potatoes in the sea or in a stream removed the dirt and sand. Gradually the other macaques in her group learned to wash their potatoes.

The documentation of this “pre-cultural” transmission of behavior was unusual in primatology; but not unusual enough for Watson, who suspected that supernatural mechanisms were at work on Koshima Islet. In his story, after a threshold was reached and the hundredth monkey had learned of washing potatoes, the behavior spread by a sort of mass consciousness to the entire group, and even spontaneously leaped across the sea to groups of monkeys on other islands and the mainland.

Masao Kawai was one of the senior researchers working on the original macaque project. In 1984, while researching the HMP, Ron Amundson contacted Kawai, who was then director of the Primate Research Institute and chief editor of the journal Primates. A brief account of Watson’s claims and a list of Amundson’s doubts were sent to Kawai, along with a request to reproduce one of the macaque photos from the journal. Unfortunately, Kawai was just about to leave on a research trip to Cameroon. Through an intermediary he was able to forward permission for use of the photo “only for your own article in which you criticize Mr. Watson for falsely describing the Japanese monkey studies.” The intermediary reported: “He (Kawai) told me that you are quite right.” That article, “The Hundredth Monkey Phenomenon,” was published in the Summer 1985 Skeptical Inquirer.

More details garnered recently from Kawai are of interest because of Watson’s explanation of his sources. In 1979 Watson claimed his information came from “personal anecdotes and bits of folklore amongst primate researchers"; and in 1986, in a response to Amundson’s SI critique, Watson mentioned “off-the-record conversations with those familiar with the potato-washing work.” Are these reliable sources of information?

Markus Pössel successfully contacted Kawai recently and asked him about Watson’s claims and sources of knowledge. The three questions asked are followed by Kawai’s responses:

  1. Is Kawai aware of any sweet potato washing or other skills that propagated more rapidly than would be expected by normal, individual, “pre-cultural” propagation?

    Answer: No.

  2. Is Kawai aware of the spontaneous and rapid spread of sweet potato washing from Koshima to groups of macaques on other islands and on the mainland?

    Answer: Individual monkeys in other groups or in zoos may have accidentally learned washing behavior, but it hasn't been observed anywhere on Koshima that washing behavior has spread to other group members.

  3. Has Kawai heard any “anecdotes or bits of folklore” among his primatologist colleagues regarding rapid behavior propagation, and does he know of any contacts between Lyall Watson and his (Kawai’s) colleagues?

    Answer: No. Kawai believes that the idea of telepathy may have been introduced by Western countries.

So much for the New Age image of the “mystical” East. Kawai, the best possible source of information on the Koshima macaques, considers the mass consciousness reported by Watson to have been a Western import.

The only mysterious, abrupt spread that remains to be accounted for is the continued ubiquity of the HMP story in New Age literature.


  1. See “The Hundredth Monkey Phenomenon” and "Watson and the Hundredth Monkey Phenomenon,” by Ron Amundson, SI, Summer 1985, pp. 348-356; and SI, Spring 1987, pp. 303-304.

Markus Pössel & Ron Amundson

Markus Pössel and Ron Amundson

Markus Pössel is a physics student in Hamburg, Germany. His inquiries about the Hundredth Monkey Phenomenon are part of his research for a book on the German-language authors Erich von Däniken and Johannes von Buttlar.

Ron Amundson is a professor of philosophy at the University of Hawaii at Hilo.