Editing Leon Festinger (section)

===''When Prophecy Fails''===
{{main|When Prophecy Fails}}
Festinger and his collaborators, [[Henry Riecken]] and [[Stanley Schachter]], examined conditions under which disconfirmation of beliefs leads to increased conviction in such beliefs in the 1956 book ''[[When Prophecy Fails]]''. The group studied a small apocalyptic cult led by Dorothy Martin (under the pseudonym Marian Keech in the book), a suburban housewife.<ref>Festinger, Riecken, & Schachter, 1956</ref><ref>Mooney, 2011</ref> Martin claimed to have received messages from "the Guardians," a group of superior beings from another planet called 'Clarion.' The messages purportedly said that a flood spreading to form an inland sea stretching from the Arctic Circle to the Gulf of Mexico would destroy the world on December 21, 1954. The three psychologists and several more assistants joined the group. The team observed the group firsthand for months before and after the predicted apocalypse. Many of the group members quit their jobs and disposed of their possessions in preparation for the apocalypse. When doomsday came and went, Martin claimed that the world had been spared because of the "force of Good and light"<ref>Festinger, Riecken, & Schachter, 1956, p. 169</ref> that the group members had spread. Rather than abandoning their discredited beliefs, group members adhered to them even more strongly and began proselytizing with fervor.

Festinger and his co-authors concluded that the following conditions lead to increased conviction in beliefs following disconfirmation:

:1. The belief must be held with deep conviction and be relevant to the believer's actions or behavior.
:2. The belief must have produced actions that are arguably difficult to undo.
:3. The belief must be sufficiently specific and concerned with the real world such that it can be clearly disconfirmed.
:4. The disconfirmatory evidence must be recognized by the believer.
:5. The believer must have social support from other believers.<ref>Festinger, Riecken, & Schachter, 1956, p. 4</ref>

Festinger also later described the increased conviction and proselytizing by cult members after disconfirmation as a specific instantiation of cognitive dissonance (i.e., increased proselytizing reduced dissonance by producing the knowledge that others also accepted their beliefs) and its application to understanding complex, mass phenomena.<ref>Festinger, 1957, pp. 252–259</ref>

The observations reported in ''When Prophecy Fails'' were the first experimental evidence for [[belief perseverance]].{{citation needed|date=February 2020}}