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Illusory Truth Effect

Also Known As: Reiteration Effect Validity Effect Repetition-Based Truth Effect
Cognitive Bias ID: illusory_truth_effect

Definition

The illusory truth effect is the tendency to believe information is true after repeated exposure, regardless of its actual veracity. Repetition increases processing fluency, which the brain misinterprets as a signal of truth. This effect persists even when people initially knew the information was false or when the source is known to be unreliable.

Examples

A false claim that 'we only use 10% of our brains' has been repeated so often in popular culture that many people accept it as scientific fact, despite neuroscientists consistently debunking it.

During an election campaign, a candidate repeatedly claims that the country's crime rate is 'the highest it has ever been.' Despite the claim being statistically false, polls show that a large portion of voters believe crime is at a record high by the end of the campaign.

A gym chain's slogan — 'Lactic acid is what causes muscle soreness after exercise' — appears on posters, social media, and merchandise for years. Although exercise scientists have long known this to be inaccurate, many gym-goers and even some trainers confidently repeat it as fact.

Verification Steps
Verification Steps
Binary yes/no questions that an AI must answer to detect a reasoning pattern in a text.
Each of the 452 aspects has verification steps — simple yes/no questions designed to systematically detect whether a pattern appears in a text. For ad hominem: "Does the argument attack a person rather than their claim?" For false dichotomy: "Are only two options presented when more exist?" This ensures consistent, reproducible analysis.

Binary (yes/no) questions an LLM must answer to identify this aspect:

  1. 1

    Is a claim or statement repeated multiple times?

    Type: binary
  2. 2

    Is the repetition serving as the primary basis for believing it?

    Type: binary
  3. 3

    Is there a lack of independent evidence beyond the repeated assertion?

    Type: binary
Deep Dive
The expandable detail section on each aspect page with examples, psychology, and counter-strategies.
The Deep Dive section provides in-depth information about each aspect: a real-world example showing the pattern in action, an explanation of why it works psychologically, practical advice on how to counter it, alternative names, and links to related aspects.