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

People judge repeated statements as more true than new statements: a truth effect. In three preregistered experiments (N = 463), we examined whether people predict others’ truth judgments to be more biased by repetition than their own: a bias blind spot for the truth effect. In Experiment 1, using uncertain but moderately plausible statements, participants predicted repetition to increase truth judgments in general. There was no significant difference between predictions for the self and others. Experiment 2 used implausible statements and found a significant bias blind spot: participants predicted a larger effect of repetition for others than for themselves. Experiment 3 considered again moderately plausible statements, but this time in a larger sample of participants. Critically, we compared actual performance after a two-day delay with participants’ predictions for the self and others. This experiment replicated the bias blind spot. Importantly, participants underestimated the magnitude of the truth effect. Finally, predictions and actual truth effect scores were not significantly related to each other. Overall, the results highlight that although people assume repetition to influence their truth judgments, they generally underestimate the effect’s magnitude, particularly for themselves.