Abstract
Over the last four decades, studies provided evidence that individuals tend to rate statements as being more truthful when they are re-exposed to them, the so-called ‘illusory truth effect’. In light of a growing number of studies published since the previous meta-analysis in 2006 and concern of publishing biases, we conduct a meta-analysis on 182 studies and 366 effect sizes (N = 31,184 participants) published from 1977 to 2025. After correcting for small-study effects, we observe a small illusory truth effect (g = 0.37, 95% confidence interval [0.30, 0.44]), with a substantial within and between-study heterogeneity. Here, we show that multiple variables accounted for such heterogeneity, including the type of item, the instructions during the first exposure, the presence of veracity cues, and the duration of presentation on first exposure to the statement. We highlight the importance of the initial exposure and discuss practical implications regarding the current misinformation crisis.
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Data availability
The data generated in this study is available in the Open Science Framework (OSF) repository under accession85 https://doi.org/10.17605/OSF.IO/2DB8S. No raw individual-level participant data were generated in this study. The processed data underlying all analyses, including extracted effect sizes, moderator coding, and imputed datasets, are available in the OSF repository. No data are subject to ethical, legal, or commercial restrictions.
Code availability
All analysis scripts used to perform the meta-analyses and generate the figures in this study are available in the OSF repository under accession https://doi.org/10.17605/OSF.IO/2DB8S.
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Acknowledgements
We would like to thank Y. Al-Bandakji for her help in double-coding during data extraction, as well as A. De Carvalho for his valuable feedback on systematic review processes. We would also like to thank E.L. Henderson for sharing her materials. S.Y., M.G., M.C., and G.B. received funding from FakeAd ANR grant ANR−21-CE28-0025. S.Y. received fundings from a CIFRE grant 2022/1463 administered by the ANRT (Association Nationale de la Recherche et de la Technologie). The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication.
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S.Y. contributed to conceptualization, methodology, formal analysis, investigation, data curation, visualization, writing—original draft preparation, and writing—review & editing. D.A. contributed to methodology, formal analysis, visualization, and writing—review & editing. M.G. contributed to methodology, investigation, and writing—review & editing. A.C. contributed to formal analysis, visualization, and writing—review & editing. M.C. and G.B. contributed to conceptualization, methodology, supervision, project administration, and writing—review & editing.
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S.Y., M.C., and G.B. were authors of one study included in this review. However, this study was evaluated using the same inclusion criteria and risk of bias assessment as all other studies. The remaining authors declare no competing interests.
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Ye, S., Attali, D., Ghazi, M. et al. Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70041-x
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DOI: https://doi.org/10.1038/s41467-026-70041-x
