But where Mr. Festinger found the richest raw material for his theory was in a cult that developed in Chicago in 1954. A woman Mr. Festinger called Marion Keech claimed she was receiving messages from another planet, Clarion. The messages predicted that on a given date, a cataclysmic flood would engulf most of the continent. Those who joined Mrs. Keech's sect would be picked up by flying saucers and evacuated from the planet.
A brief newspaper story about the cult came to the attention of Mr. Festinger. He was reminded of the followers of a New England farmer, William Miller, who predicted that the Second Advent of Christ would occur in 1843. Thousands of people who believed Miller's prophecy prepared for the world to end. But 1843 passed without incident. Far from admitting that the prediction was wrong, the Millerites attempted to lessen their cognitive dissonance in two ways: They changed the date of the Second Advent to the following year and stepped up their campaign, trying to convince even more people that their belief was right.
Mr. Festinger and two colleagues infiltrated Mrs. Keech's movement, acting as participants for three months. They watched as about two dozen well-educated, upper-middle-class people, "who led normal lives and filled responsible roles in society," quit their jobs and threw away their possessions. Before the dates of the expected flood, the cult was mostly averse to publicity and had no interest in attracting other believers.
On the day before the flood, the group was told that at midnight a man would appear at Mrs. Keech's house and take them to a flying saucer. But no knock came at her door, and the group struggled to find an explanation for why there would be no flying saucer or flood. At 4:45 a.m., the group said, a message arrived from God saying He had stayed the flood because of their strength.
What interested Mr. Festinger was not so much this face-saving explanation as what the cult members did in the following weeks. Rather than shunning public attention as they had before, they began zealously proselytizing. "There were almost no lengths to which these people would not go now to get publicity and to attract potential believers," Mr. Festinger wrote. "If more converts could be found, then the dissonance between their belief and the knowledge that the prediction hadn't been correct could be reduced."
Link to Pittsburg Post-Gazette, a reprint of an earlier WSJ article:
(Amusingly, it might be noted that a belief in another Noah's Flood
is the underpinning device in Chaucer's The Miller Tale,
writ 600 years ago. So perhaps Chaucer's not all that remote!)