Repetition increases Perceived Truth even for Known Falsehoods

Repetition increases belief in false statements. This illusory truth effect occurs with many different types of statements (e.g., trivia facts, news headlines, advertisements), and even occurs when the false statement contradicts participants’ prior knowledge. However, existing studies of the effect of prior knowledge on the illusory truth effect share a common flaw; they measure participants’ knowledge after the experimental manipulation and thus conditionalize responses on posttreatment variables. In the current study, we measure prior knowledge prior to the experimental manipulation and thus provide a cleaner measurement of the causal effect of repetition on belief. We again find that prior knowledge does not protect against the illusory truth effect. Repeated false statements were given higher truth ratings than novel statements, even when they contradicted participants’ prior knowledge.