·Psychology & Behavior
Section 1
The Core Idea
In 1977, Lynn Hasher, David Goldstein, and Thomas Toppino ran an experiment that should have rewritten every communications playbook. They presented subjects with plausible statements — some true, some false — and repeated a subset in later sessions. Repeated statements were rated as more true than novel statements, regardless of actual truth. "The Eiffel Tower is in England" feels more true after you've seen it three times. Repetition didn't just increase familiarity. It increased belief.
The mechanism is processing fluency. When you encounter a statement for the second or third time, your brain processes it faster. The brain misinterprets that fluency — that cognitive ease — as a signal of accuracy. The inferential chain happens below conscious awareness: this feels easy to process, things that are true tend to feel easy, therefore this is probably true. You don't decide to believe a repeated claim. You just do.
Fazio, Brashier, Payne, and Marsh (2015) demonstrated that repetition increases perceived truth even when subjects are explicitly told the statement is false. Even when they have prior knowledge that contradicts the claim. Even when warned about the effect in advance. The fluency signal is so automatic that conscious knowledge cannot fully override it.
The counter-evidence is sobering. Ecker, Lewandowsky, and Tang (2010) found that explicit warnings before exposure can reduce the illusory truth effect — but not eliminate it. Even forewarned subjects show some truth-inflation for repeated claims. The effect is dampened, not defeated. The only reliable structural defence is source-tracking: forcing yourself to ask "where did I first hear this, and what was the evidence?" before accepting a claim as true. That discipline breaks the fluency-to-truth inference by redirecting the evaluation from "does this feel true?" to "is this supported?" Almost no one does it consistently.
Marketing understood this before psychology named it. "Just Do It" has been repeated billions of times since 1988. Nike doesn't repeat the slogan because people forget it. They repeat it because each repetition increases the fluency of the association between Nike and decisive action — and that fluency gets misread as truth. The brand message stops being a claim and starts being a fact. Coca-Cola's "Open Happiness." McDonald's "I'm Lovin' It." These aren't taglines. They're truth-manufacturing loops.
Political campaigns, advertising, propaganda — all exploit the same mechanics. Joseph Goebbels reportedly understood that a lie repeated often enough becomes accepted as truth. The mechanism isn't persuasion in the traditional sense. There's no argument, no evidence. There's just repetition producing fluency producing the feeling of truth. The strategic implication: repetition builds belief. Use it ethically.
