EffectBelief updating · Truth Judgment · Entry 87
Illusory Truth Effect – when repeated lies start to feel like truth
Do statements seem more true the more you hear them? That’s Illusory Truth Effect – the tendency to believe information simply because it’s familiar or easy to process.
Where it can show up
- Fake news & propaganda – false facts start feeling true when they’re repeated often enough.
- Marketing & advertising – slogans like “natural product” create an illusion of healthiness, even when it’s not true.
- Social media – posts with many likes and shares feel more credible, even if they lack facts.
A practical countermeasure
- Check sources, not just frequency – just because something sounds familiar doesn’t make it true.
- Be skeptical of repeated claims – if a phrase is everywhere, that doesn’t mean it’s accurate.
- Don’t trust ease of understanding – easy to process ≠ correct.
Evidence review
robustWhat the evidence supports
Repeated information is, on average, judged as more truthful than comparable new information. The size of the effect varies with the material and procedure, and repetition does not make every claim believable or erase all prior knowledge.
How researchers describe the pattern
Repetition can make information easier or more coherent to process and retrieve. People can then use that subjective ease or familiarity as one cue when judging truth, even though repetition itself is not evidence that the statement is correct.
Practical interpretation
When a claim feels true mainly because it sounds familiar, switch from familiarity to source checking. Ask where the claim came from and what evidence would support it. Do not treat familiarity as proof, but do not treat repetition as proof of falsehood either.
Reviewed sources
- Frequency and the conference of referential validity foundational experiment · 1977 · DOI 10.1016/S0022-5371(77)80012-1
- The effects of repetition frequency on the illusory truth effect experiments · 2021 · DOI 10.1186/s41235-021-00301-5
- The illusory truth effect: A review of how repetition increases belief in misinformation review · 2024 · DOI 10.1016/j.copsyc.2023.101736
Editorial review: 2026-08-18. Evidence status describes this entry, not every study ever published on the topic.