Paid $1 to lie about a boring task, people ended up believing the lie
In 1959, Festinger and Carlsmith had participants tell a waiting 'subject' that a tedious task was fascinating, paying some $1 and others $20 to do it. The $1 liars later rated the task as genuinely more enjoyable than the $20 liars — with too little external reward to justify lying, they resolved the discomfort by changing what they actually believed.