Why was “Japanese collectivism” established as the symbolic image of Japanese culture although it is unreal? The notion of “Japanese collectivism” was formed in the West about 140 years ago. A Westerner who highly valued individualism and believed that Japan is opposite to the West visited Japan and published a book in which he claimed that Japanese lack individuality. His view was widely accepted by Westerners who also highly valued individualism. Under the influence of this prevailing view, American anthropologist Ruth Benedict studied Japan for one year as a member of the U.S. government during World War II. During the American occupation of Japan, she published her study as a book in which she delineated Japanese culture as a collectivistic one. Her book was widely read by the personnel of the U.S. government and Occupation Army as a guide on how to deal with the Japanese. The prestige of Americans during the occupation period made Japanese accept “Japanese collectivism” as the basic nature of Japanese culture. Once established, the notion of “Japanese collectivism” was sustained by various cognitive biases such as confirmation bias and belief perseverance.