Pearl Harbor Rumors [...]

Allport undertook early investigations [Allport and Postman,
1946, Allport and Postman, 1947] in the context of wartime rumours. He posited the importance of studying rumours, emphasising that “newsworthy events are likely to breed rumors” and that “the amount of rumor in circulation will vary with the importance of the subject to the individuals involved times the
ambiguity of the evidence pertaining to the topic at issue”. This led him to set forth a motivational question which is yet to be answered: “Can rumors be scientifically understood and controlled?” [Allport and Postman, 1946]. His 1947 experiment [Allport and Postman, 1947] reveals an interesting fact about
rumour circulation and belief. He looked at how US President Franklin D. Roosevelt allayed rumours about losses at the 1941 Pearl Harbor bombing. The study showed that before the President made his address, 69% of a group of undergraduate students believed that losses at Pearl Harbor were greater than officially stated; but five days later, the President having spoken in the meantime, only 46% of an equivalent group of students believed this statement to be true. This study revealed the importance of an official announcement by a reputable person in shaping society’s perception of the accuracy of a rumour. (Source)