People underestimate the influence of repetition on truth judgments (and more so for themselves than for others)


  • Mattavelli Simone
  • Béna Jérémy
  • Corneille Olivier
  • Unkelbach Christian

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People judge repeated statements as more truthful than new statements: a truth effect. In three pre-registered experiments (N = 463), we examined whether people expect repetition to influence truth judgments more for others than for themselves: a bias blind spot in the truth effect. In Experiments 1 and 2, using moderately plausible and implausible statements, respectively, the test for the bias blind spot did not pass the significance threshold set for a two-step sequential analysis. Experiment 3 considered moderately plausible statements but with a larger sample of participants. Additionally, it compared actual performance after a two-day delay with participants' predictions for themselves and others. This time, we found clear evidence for a bias blind spot in the truth effect. Experiment 3 also showed that participants underestimated the magnitude of the truth effect, especially so for themselves, and that predictions and actual truth effect scores were not significantly related. Finally, an integrative analysis focusing on a more conservative between-participant approach found clear frequentist and Bayesian evidence for a bias blind spot. Overall, the results indicate that people (1) hold beliefs about the effect of repetition on truth judgments, (2) believe that this effect is larger for others than for themselves, (3) and underestimate the effect's magnitude, and (4) particularly so for themselves.

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