[1][2][3][4][5] One of the primary factors in the spread of this concept is that many authors quote secondary, tertiary, or post-tertiary sources that have themselves misrepresented the original observations.
[1] Between 1952 and 1953,[i] primatologists conducted a behavioral study of a troop of Macaca fuscata (Japanese macaque or Snow monkeys) on the island of Kōjima.
[1] An unanticipated byproduct of the study was that the scientists witnessed several innovative evolutionary behavioral changes by the troop, two of which were orchestrated by one young female, and the others by her sibling or contemporaries.
[1] According to Watson, the scientists observed that some of the monkeys learned to wash sweet potatoes, initially through an 18-month-old female member (named "Imo" by the researchers) of the troop in 1953.
The Koshima troop was identified as segregated from other monkeys and, from 1950, used as a closed study group to observe wild Japanese macaque behavior.
[8] Unfortunately, Keyes combined two items of truth: that the Koshima monkeys learned to wash sweet potatoes, and that the phenomenon was observed on neighboring islands.
[1] Separate papers make mention that, from 1960 onward, similar sweet potato-washing behaviors were noticed in other parts of the world, however this is not directly attributed to Koshima.
[3] In her review, she found that the original research reports by the Japan Monkey Centre in the 2nd, 5th, and 6th volumes of Primates were insufficient to support Watson's story.
[citation needed] In his book Why People Believe Weird Things (1997), Michael Shermer explains how the urban legend started, was popularized, and has since been discredited.
[9][10][11] An analysis of the appropriate literature by Ron Amundson, published by The Skeptics Society, revealed several key points that demystified the supposed effect.