Why can a repeated claim seem more true?

A claim encountered before appears, on average, truer than a comparable new claim, without any additional probative information. This illusory truth effect concerns both true and false statements: it relates to their perceived truth, not their accuracy.^{1PII: S0022-5371(77)80012-1Journal of Verbal Learning and Verbal Behavior · 19772Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications3The Trajectory of Truth: A Longitudinal Study of the Illusory ...Journal of Cognition · 2021}

1977: repeating without adding evidence

According to the original scientific article on the foundational 1977 experiment, the analysis covers 40 students, after excluding ten people who were absent from at least one session. Each session includes 60 claims, 20 of which are repeated across the three sessions, held two weeks apart.^{1PII: S0022-5371(77)80012-1Journal of Verbal Learning and Verbal Behavior · 1977}

In this experiment, validity judgments increase for repeated claims, both true and false, unlike non-repeated claims.^{1PII: S0022-5371(77)80012-1Journal of Verbal Learning and Verbal Behavior · 19778The effects of repetition frequency on the illusory truth effect - Cognitive Research: Principles and ImplicationsCognitive Research: Principles and Implications · 2021}

According to the authors of the scientific study The effects of repetition frequency on the illusory truth effect, published in 2021 in Cognitive Research: Principles and Implications, two experiments present claims up to 9 and then 27 times, followed by an evaluation one week later. They report a logarithmic increase in perceived truth: additional repetitions continue to have an effect, with diminishing gains. The versions of this article accessible on different platforms constitute a single publication.^{5The effects of repetition frequency on the illusory truth effect - PMCCognitive Research: Principles and Implications · May 13, 20219The effects of repetition frequency on the illusory truth effect | Cognitive Research: Principles and Implications | Springer Nature LinkCognitive Research: Principles and Implications · May 13, 2021}

According to the authors of the scientific systematic review and meta-analysis published in 2026 in Nature Communications, their synthesis brings together 182 studies, 366 effect sizes and 31,184 participants for the period from 1977 to 2025. After correcting for effects related to small studies, they estimate a small effect, g = 0.37, with a 95% confidence interval from 0.30 to 0.44, and report substantial heterogeneity.^{2Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications}

Historical and recent estimates are not directly interchangeable. According to the authors of the 2021 study in Cognitive Research: Principles and Implications, an earlier meta-analysis gave d = 0.53 for verbatim repetitions compared with new information, whereas the authors of the 2026 synthesis report g = 0.37 after correcting for effects related to small studies. The corpora, measures and corrections differ.^{5The effects of repetition frequency on the illusory truth effect - PMCCognitive Research: Principles and Implications · May 13, 20212Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications}

According to the authors of the 2026 meta-analysis, the historical estimate is d = 0.39 when comparing the same statement between exposure and test, versus d = 0.53 when comparing repeated and new statements at test. For this second comparison, they report d = 0.53, whereas the authors of the scientific systematic mapping published in Psychonomic Bulletin & Review give d = 0.50 under a random-effects model. The unavailability of the original coded data makes it impossible to reconstruct this discrepancy precisely.^{2Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications10A reproducible systematic map of research on the illusory truth effect | Psychonomic Bulletin & Review | Springer Nature LinkPsychonomic Bulletin & Review · October 27, 2021}

Processing fluency can become a cue to truth

The main explanation involves processing fluency: repetition makes a statement easier to process, and this ease can be interpreted as a cue to accuracy. This is an explanation of the effect, not evidence that the statement is true.^{4Knowledge does not protect against illusory truth.Journal of Experimental Psychology: General · 201511A referential theory of the repetition-induced truth effect3The Trajectory of Truth: A Longitudinal Study of the Illusory ...Journal of Cognition · 2021}

According to the authors of the scientific study Knowledge does not protect against illusory truth, published in Journal of Experimental Psychology: General, the effect can appear even when participants know the correct answer, whereas the authors of Competing cues: Older adults rely on knowledge in the face of fluency, published in Psychology and Aging, observe among the older adults studied an effect only when relevant knowledge is lacking. The populations and protocols differ; these findings do not support the conclusion that knowledge would always be useless.^{4Knowledge does not protect against illusory truth.Journal of Experimental Psychology: General · 201512Competing cues: Older adults rely on knowledge in the face of fluency.Psychology and Aging · 2017}

Familiarity should not be confused either with conscious memory of a previous encounter. According to the author of the 1979 scientific experiment Credibility of repeated statements: Memory for trivia, published in Journal of Experimental Psychology: Human Learning and Memory, the effect depended on subjective recognition of the repetition. Whereas this experiment reports that result, the authors of the 2021 longitudinal study The Trajectory of Truth, published in Journal of Cognition, present a model allowing for familiarity without conscious memory of the exposure. This theoretical proposal, on its own, does not demonstrate an effect of subliminal exposure.^{13Credibility of repeated statements: Memory for trivia.Journal of Experimental Psychology: Human Learning and Memory · 19797The Trajectory of Truth: A Longitudinal Study of the Illusory Truth Effect | Journal of CognitionJournal of Cognition}

According to the authors of the scientific document on the cognitive processes underlying the truth effect, disseminated by the University of Freiburg, some mechanisms associated with repetition decrease as the retention interval increases. The document announces public access to the data and code; its editorial status remains to be clarified.^{14Running head: COGNITIVE PROCESSES UNDERLYING THE TRUTH EFFECT}

Appreciating a brand more and believing a claim more are different outcomes. According to the authors of the marketing study on advertising wearout hosted by Duke University, repetition consistently improves memory for the advertisement or brand. This finding does not demonstrate increased belief in a factual claim about the product.^{15Ad wearout wearout: How time can reverse the negative effect of frequent advertising repetition on brand preferenceInternational Journal of Research in Marketing · December 15, 2018}

Two encounters may be sufficient, without a universal timeline

The main gain generally appears at the second encounter with a claim, after which additional repetitions produce smaller increases. This pattern is observed in studies of repetition frequency and validity judgments of rumours.^{5The effects of repetition frequency on the illusory truth effect - PMCCognitive Research: Principles and Implications · May 13, 20216Validity judgments of rumors heard multiple times: the shape of the truth effectTaylor & Francis Online}

According to the authors of the registered 2021 longitudinal study The Trajectory of Truth, published in Journal of Cognition, the effect appears immediately, after one day, one week and one month, but decreases as the delay increases. They report 608 participants, of whom 567 were analysed. The article and its deposits in archives describe the same study, not several independent replications.^{16The Trajectory of Truth: A Longitudinal Study of the Illusory Truth EffectJournal of Cognition · 202117The trajectory of truth: a longitudinal study of the illusory truth effectUbiquity Press · June 8, 2021}

According to the authors of this longitudinal study, the effect decreases with the delay, whereas the 2010 meta-analysis they discuss found no general relationship between delay and effect size. They also report divergent earlier findings: one experiment found no difference between one week and one month, whereas another found an effect for false claims after one week, but no longer after one or three months. The designs and measures differ; no universal duration until disappearance has been established.^{3The Trajectory of Truth: A Longitudinal Study of the Illusory ...Journal of Cognition · 20217The Trajectory of Truth: A Longitudinal Study of the Illusory Truth Effect | Journal of CognitionJournal of Cognition}

In children

Researchers Lisa K. Fazio and Carrie L. Sherry, in the scientific study The Effect of Repetition on Truth Judgments Across Development published in 2020 in Psychological Science, observe the effect in children aged 5 and 10 as well as in adults. The 2026 meta-analysis also reports observing it from age 5.^{18The Effect of Repetition on Truth Judgments Across Development - Lisa K. Fazio, Carrie L. Sherry, 2020SAGE Journals · 20202Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications}

According to Fazio and Sherry, the sample includes only 24 five-year-old children. The finding concerns experimental truth judgments, without measuring prolonged repetition in school.^{18The Effect of Repetition on Truth Judgments Across Development - Lisa K. Fazio, Carrie L. Sherry, 2020SAGE Journals · 2020}

Young children’s suggestibility is a related but distinct phenomenon. According to the authors of the scientific study How Suggestible Are Preschool Children? Cognitive and Social Factors, more interviews and a longer interval produced the strongest suggestibility; some children appeared to have internalized false suggestions to the point of resisting debriefing. This study does not make it possible to isolate the specific role of repetition.^{19How Suggestible Are Preschool Children? Cognitive and Social FactorsJ. Am. Acad. Child Adolesc. Psychiatry · 1997}

Linking a memory to its source is one possible way to reduce this suggestibility. Researchers Jessica W. Giles, Alison Gopnik and Gail D. Heyman, in their 2002 scientific study Source Monitoring Reduces the Suggestibility of Preschool Children, report a benefit from this training. The authors of a scientific synthesis published in Current Psychology on source monitoring in children also present this approach. These studies do not demonstrate identical protection against the illusory truth effect.^{20Source Monitoring Reduces the Suggestibility of Preschool Children - Jessica W. Giles, Alison Gopnik, Gail D. Heyman, 2002200221An overview of source monitoring theory and research regarding children’s training - Current PsychologyCurrent Psychology}

In science education, misconceptions can coexist with correct knowledge and resist instruction. Studies published in the scientific journal Science & Education, a scientific meta-analysis on conceptual change strategies disseminated by the Wiley publisher, and the educational website The Science Teacher converge on this finding.^{22Embracing Representational Plurality to Bypass Misconceptions in Science Education | Science & Education | Springer Nature LinkScience & Education · November 7, 202423Effectiveness of conceptual change strategies in science education: A meta‐analysisWiley Online Library24Misconceptions and conceptual change in science education - the science teacherthe science teacher}

Structured conceptual change strategies nevertheless improve science learning, with highly heterogeneous effects across studies. These studies do not make it possible to attribute students’ misconceptions to the repetition of a claim.^{23Effectiveness of conceptual change strategies in science education: A meta‐analysisWiley Online Library22Embracing Representational Plurality to Bypass Misconceptions in Science Education | Science & Education | Springer Nature LinkScience & Education · November 7, 2024}

At school: textbooks, teachers, curricula

Textbook analyses identify incomplete presentations or disputed attributions. According to an institutional post by the assessment organization Cambridge Assessment, an analysis of 138 textbooks found that many explain effect size in a simplified or incomplete manner. According to the authors of a 2011 study of physics textbooks, all the books examined still attribute the measurement of the gravitational constant to Cavendish. The number of books and their selection method must be clarified before this second result can be generalized.^{25The statistics of textbook errorsCambridge Assessment26Microsoft Word - slisko hadzibegovic ejpe revised.docEuropean Journal of Physics Education · 2011}

Representations derived from Ernst Haeckel’s embryonic drawings persisted in textbooks until the end of the twentieth century. A dissertation examines 240 secondary-school biology textbooks published between 1907 and 2010. Textbook co-author Kenneth R. Miller acknowledges on his website devoted to these books that two of his textbooks used these representations before a correction in 1998.^{27Lessons from Embryos: Haeckel's Embryo Drawings, Evolution, and Secondary Biology Textbooks.ProQuest LLC · 201428Haeckel and his EmbryosMiller and Levine · December 21, 1997}

According to the authors of the scientific study of East German textbooks published in Theory in Biosciences, embryology remained present from 1951 to 1988 despite several educational reforms. The continuity of this theme does not prove the persistence of any particular error.^{29Ernst Haeckel’s embryology in biology textbooks in the German Democratic Republic, 1951–1988 | Theory in Biosciences | Springer Nature LinkTheory in Biosciences · February 24, 2019}

The accuracy of the drawings and the scope of the biogenetic law are two distinct questions. According to the authors of the scientific text Haeckel, Embryos, and Evolution, published in Science, comparison with real embryos reveals many incorrect details. While this text identifies errors in the drawings, the authors of Haeckel’s ABC of evolution and development, published in the scientific journal Biological Reviews of the Cambridge Philosophical Society, defend a limited version of the biogenetic law applied to individual traits. This proposal does not validate the drawings.^{30(PDF) Haeckel, Embryos, and EvolutionScience · May 15, 199831Haeckel's ABC of evolution and development - PubMedBiological Reviews of the Cambridge Philosophical Society · November 2002}

According to the author of the scientific article Haeckel’s embryos: fraud not proven, published in Biology & Philosophy, fraud has not been proven. Identifying incorrect details is therefore not sufficient to establish this qualification.^{32Haeckel’s embryos: fraud not proven - Biology & PhilosophyBiology & Philosophy · 200930(PDF) Haeckel, Embryos, and EvolutionScience · May 15, 1998}

Positions diverge on the contemporary use of the drawings. According to the National Center for Science Education, textbooks and developmental biologists no longer rely on Haeckel’s work, whereas the Discovery Institute claims that the drawings persist in a large number, or even a majority, of modern textbooks. Reproducing a derived image and basing a scientific explanation on the biogenetic law are not equivalent criteria. Documented material persistence does not make it possible to determine the caption and conceptual use of each image.^{33IconsNational Center for Science Education34What do Modern Textbooks Really Say about Haeckel’s Embryos?Discovery Institute · 200727Lessons from Embryos: Haeckel's Embryo Drawings, Evolution, and Secondary Biology Textbooks.ProQuest LLC · 2014}

Neuromyths are widespread in several teaching populations. According to the authors of the 2012 scientific study Neuromyths in Education: Prevalence and Predictors of Misconceptions among Teachers, published in Frontiers in Psychology, British and Dutch teachers on average endorsed 49% of the proposed myths. A Spanish study accompanied by an international comparison also finds a high prevalence in several countries.^{35Neuromyths in education: Prevalence and predictors of misconceptions among teachersFrontiers in Psychology · October 18, 201236Neuromyths in Education: Prevalence among Spanish Teachers and an Exploration of Cross-Cultural Variation}

According to the authors of the 2012 study, greater general knowledge of the brain predicted greater endorsement of neuromyths in their sample. Reading popular media was associated both with better neuroscience literacy and with more misconceptions. These observational associations, in a voluntary sample of teachers interested in neuroscience, do not establish causality.^{37Dekker et al. - 2012 - Neuromyths in education Prevalence and predictors of misconceptions among teachers(2).pdfFrontiers in Psychology · October 18, 201235Neuromyths in education: Prevalence and predictors of misconceptions among teachersFrontiers in Psychology · October 18, 2012}

According to the authors of the scientific review Interventions to Dispel Neuromyths in Educational Settings, a review of 24 articles calculated a weighted prevalence of 52.1% among educators, with no decrease observed between 2012 and 2020. They also report an average weighted belief in visual, auditory and kinaesthetic learning styles of 89.1% across 37 samples published between 2009 and 2020, with no decline detected. The questionnaires and populations vary; these comparisons do not demonstrate a causal effect of repetition.^{38Interventions to Dispel Neuromyths in Educational Settings—A Review - PMCFrontiers in Psychology · October 13, 2021}

According to Psychology Today and Forbes, scientific or neuroscience training is associated with lower belief in neuromyths, without eliminating them. According to The Conversation, only 7% of educators surveyed in an Australian study correctly rejected the claim about the effectiveness of learning styles.^{39Debunking Neuromyths: Eight Common Brain Myths Set StraightPsychology Today · August 10, 201740Debunking The ‘Learning Style’ NeuromythForbes · December 4, 202341Students are neither left nor right brained: how some early childhood educators get this ‘neuromyth’ and others wrongThe Conversation}

According to the specialized media outlet Education Week, an international study indicates that most teachers encountered neuromyths in initial or continuing education rather than in the media; the primary publication corresponding to this result remains to be identified. The authors of a multilingual scientific tool for diagnosing neuromyths also note that linguistic adaptations and structural checks of earlier questionnaires are rarely carried out or reported, which weakens some international comparisons.^{42The Top 5 Myths Elementary Teachers Believe About the Science of LearningEducation Week · September 202543Construction and validation of a multilingual diagnostic ...International Journal of Assessment Tools in Education · 2025}

According to Quebec’s Ministry of Education, educational resource packages are evaluated according to ministerial criteria, may be subject to corrections requested from the publisher, and are entered on an official list after approval. Ministerial documents and educational resource pages devoted to the CCQ program also indicate that materials may be used without this status, even when they display compliance with the program.^{44Matériel didactique utilisé pour l’enseignement des programmes d’étudesGouvernement du Québec · August 26, 202545Schéma approbation des ensembles didactiques et des ouvrages de référenceMinistère de l’Éducation du Québec46CCQ - Maisons d'éditionCCQ47CCQ CSSDN - Matériel didactique et situations d'apprentissageCCQ CSSDN · July 15, 2026}

These findings document the persistence of representations in textbooks and beliefs among teachers. They do not establish that repetition of an assertion in class for years is the cause.^{27Lessons from Embryos: Haeckel's Embryo Drawings, Evolution, and Secondary Biology Textbooks.ProQuest LLC · 201438Interventions to Dispel Neuromyths in Educational Settings—A Review - PMCFrontiers in Psychology · October 13, 202110A reproducible systematic map of research on the illusory truth effect | Psychonomic Bulletin & Review | Springer Nature LinkPsychonomic Bulletin & Review · October 27, 2021}

Even the implausible? A boundary still under debate

According to the authors of the 2021 study published in Cognitive Research: Principles and Implications, earlier experiments observed the effect for highly implausible assertions, whereas the authors of the 2026 meta-analysis published in Nature Communications conclude that the increase is not reliable for extremely implausible assertions. The degrees of implausibility, statements and protocols may differ. This comparison establishes no general threshold.^{5The effects of repetition frequency on the illusory truth effect - PMCCognitive Research: Principles and Implications · May 13, 20212Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications}

According to the authors of the preprint on highly implausible statements deposited on the OSF platform, approximately half of participants show no effect or an inverse effect in an exploratory analysis. This result concerns a particular protocol and does not permit generalization to every implausible assertion.^{48truth-by-repetition effect for highly implausible statements - OSFUCLouvain}

Advertising, politics and media: what the examples show

According to the authors of the scientific study on repetition and attention to accuracy in an advertising context, published in Cognitive Research: Principles and Implications, two experiments found the effect after a single reading in contexts containing 20% and 60% advertising content, but not when accuracy was assessed upon first exposure. These experiments measure the perceived truth of claims about products.^{49The illusory-truth effect and its absence under accuracy-focused processing are robust across contexts of low and high advertising exposure | Cognitive Research: Principles and Implications | Springer Nature LinkCognitive Research: Principles and Implications · May 13, 2025}

According to the authors of the scientific study published in the International Journal of Communication on the repetition of negative political messages, repetition can reduce their credibility while worsening attitudes toward the issue concerned. The abstract does not make it possible to specify the magnitude of these results.^{50Effects of Message Repetition and Negativity on Credibility Judgments and Political AttitudesInternational Journal of Communication · August 14, 2017}

BBC World Service lists several broadcasts, from 4 to 6 July 2020, of its programme devoted to the theory linking 5G and coronavirus. This programming page establishes broadcast dates; it does not demonstrate the programme’s detailed content or the repetition of an identical formula by several independent media outlets.^{51BBC World Service - Trending, Who spread the ‘5G coronavirus’ conspiracy theory?BBC World Service · July 4, 2020}

Verbatim repetition produces the classic effect and is the form studied primarily. Semantic consistency across exposures matters: repeating only a theme or referents is generally insufficient, and a semantically incompatible repetition can reduce perceived truth.^{52The illusory truth effect requires semantic coherence across repetitionsScienceDirect5The effects of repetition frequency on the illusory truth effect - PMCCognitive Research: Principles and Implications · May 13, 20212Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications53Perceived truth of statements and simulated social media postings: an experimental investigation of source credibility, repeated exposure, and presentation format | Cognitive Research: Principles and Implications | Springer Nature LinkCognitive Research: Principles and Implications · November 11, 2020}

According to the authors of the 2024 scientific study on repetitions of general meaning, published by the publisher Taylor & Francis, these repetitions and verbatim repetitions produce elevated and relatively similar beliefs without correction, whereas the authors of The illusory truth effect requires semantic coherence across repetitions, disseminated on the Elsevier ScienceDirect publisher platform, find no significant effect of their other manipulations in the first three experiments. The manipulations differ: repeating the general meaning of information is not equivalent to exposure only to its theme or to certain referents. These results do not allow a comparison under a constant protocol.^{54False information is harder to debunk after gist repetitions than verbatim repetitionsTaylor & Francis · 202452The illusory truth effect requires semantic coherence across repetitionsScienceDirect}

According to the authors of the 2024 study, a subsequent correction is less effective after repetition of the general meaning than after repetition word for word.^{54False information is harder to debunk after gist repetitions than verbatim repetitionsTaylor & Francis · 2024}

What can reduce the effect

According to the authors of the scientific study on initial attention to headline accuracy, published in Cognitive Research: Principles and Implications, two experiments involving a total of 575 participants found the effect after an initial evaluation of interest, but not after an initial evaluation of truthfulness. Experiments on advertising claims found protection associated with this initial attention to accuracy.^{55An initial accuracy focus reduces the effect of prior exposure on perceived accuracy of news headlines | Cognitive Research: Principles and Implications | Springer Nature LinkCognitive Research: Principles and Implications · November 5, 202049The illusory-truth effect and its absence under accuracy-focused processing are robust across contexts of low and high advertising exposure | Cognitive Research: Principles and Implications | Springer Nature LinkCognitive Research: Principles and Implications · May 13, 2025}

The interventions are nevertheless not equivalent. According to the authors of the 2026 meta-analysis, a label explicitly indicating that content is false eliminates the effect in some of the studies reviewed, whereas the authors of the longitudinal study published in Journal of Cognition report persistence despite certain warnings or prior indications of truthfulness. The authors of the scientific study on individual differences published in Psychonomic Bulletin & Review also report attenuation, without elimination, through warnings. Their wording, timing and availability at the time of judgment differ.^{2Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications7The Trajectory of Truth: A Longitudinal Study of the Illusory Truth Effect | Journal of CognitionJournal of Cognition56A psychometrics of individual differences in the truth effect | Psychonomic Bulletin & Review | Springer Nature LinkPsychonomic Bulletin & Review · September 23, 2026}

Source credibility increases truth judgments, but prior exposure retains an independent effect. According to the authors of the 2026 meta-analysis, the usefulness of a reliability indication may also depend on whether it is recalled at the time of judgment.^{53Perceived truth of statements and simulated social media postings: an experimental investigation of source credibility, repeated exposure, and presentation format | Cognitive Research: Principles and Implications | Springer Nature LinkCognitive Research: Principles and Implications · November 11, 20202Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications}

Researchers Xingyu Liu, Li Qi, Laurent Wang and Miriam J. Metzger, in their 2023 scientific study Checking the Fact-Checkers, published by SAGE, report a positive association between the fact-checker's perceived credibility and the effectiveness of the correction. This association does not demonstrate that simply displaying a name neutralizes repetition.^{57Checking the Fact-Checkers: The Role of Source Type, Perceived Credibility, and Individual Differences in Fact-Checking Effectiveness - Xingyu Liu, Li Qi, Laurent Wang, Miriam J. Metzger, 2023SAGE Journals · 2023}

According to the authors of the scientific article Can corrections spread misinformation to new audiences?, three experiments involving a total of 1,718 participants did not find that a correction exposing people to new false information generally strengthened false beliefs. Recalling the error in a correction therefore does not necessarily cause reinforcement through familiarity.^{58Can corrections spread misinformation to new audiences? Testing for the elusive familiarity backfire effect2Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications}

Traceability

Funding and conflict of interest statements must be distinguished from experimental results. Failure to verify a statement does not allow one to conclude that no funding existed.

The limitations of a laboratory effect

The literature relies largely on Western convenience samples, word for word repetitions and short delays. These characteristics limit generalization to natural media environments.^{62A reproducible systematic map of research on the illusory truth effect2Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications}

According to the authors of the scientific systematic mapping published in Psychonomic Bulletin & Review, replicability and robustness can be verified for only a small number of studies, notably because of a lack of external replications, preregistrations, and accessible data and code. According to the authors of the 2026 meta-analysis, small studies with negative or nonsignificant results are underrepresented, this finding does not demonstrate the cause of that underrepresentation.^{62A reproducible systematic map of research on the illusory truth effect2Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications}

According to researchers Reed Orchinik, David G. Rand and Rahul Bhui, affiliated with MIT Sloan in their preprint The not so illusory truth effect: A rational foundation for repetition effects, a preregistered experiment involving 4,947 participants found a markedly reduced effect in an environment where most information is false. This result remains a preprint.^{61The not so illusory truth effect: A rational foundation for repetition effectsFebruary 6, 2025}

What repetition proves, and what it does not prove

Recognizing a sentence and having evidence are two distinct things. Repetition can increase perceived truth without providing additional supporting information, while directing attention to accuracy can reduce this influence. These experiments do not allow one to infer the truth of a claim from its frequency, or to attribute an intention to those who repeat it.^{2Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants - Nature CommunicationsNature Communications3The Trajectory of Truth: A Longitudinal Study of the Illusory ...Journal of Cognition · 202155An initial accuracy focus reduces the effect of prior exposure on perceived accuracy of news headlines | Cognitive Research: Principles and Implications | Springer Nature LinkCognitive Research: Principles and Implications · November 5, 202049The illusory-truth effect and its absence under accuracy-focused processing are robust across contexts of low and high advertising exposure | Cognitive Research: Principles and Implications | Springer Nature LinkCognitive Research: Principles and Implications · May 13, 2025}