People experience psychological discomfort when holding contradictory beliefs and act to reduce it.
Festinger and Carlsmith's 1959 induced-compliance experiment: subjects paid a dollar to describe a dull task as interesting later rated it more enjoyable than those paid twenty. The canonical doomsday-cult account in When Prophecy Fails is now seriously disputed by archival research.
In practice
- A committee that has approved a policy defends it more vigorously after the first evidence against it than before.
- A buyer who has just paid over the odds reads every subsequent review as confirmation they chose well.