The Illusion-of-Truth Effect – Arizona Forensic Services, LLC

Snap Shot

The question: Does hearing a claim repeatedly make it seem more true, and if so, what does that mean for repeated interviews, pretrial publicity, argument, and instructions to disregard?

What the research shows: Repeated statements are rated as more likely to be true than new ones, a small but reliable effect found in a 2026 meta-analysis of 182 studies. It occurs for true and false statements, for implausible claims, and sometimes even when people know the correct answer. Repeating misleading claims about a witnessed event increases both their adoption and confidence in them.

What it does not show: The research measures ratings of trivia and news statements, not verdicts, and it cannot show that repetition changed a particular witness’s memory or a particular juror’s view. Corrections that repeat a false claim usually reduce belief rather than increase it, and attention to accuracy at first exposure weakens the effect.

The law: Expert testimony on the effect is general and educational under Rule 702 and Houser, and in Arizona under Chapple, Nordstrom, and Salazar-Mercado. The law presumes that jurors follow instructions (Richardson v. Marsh) while recognizing exceptions (Bruton), and Arizona treats an admonition as generally curative unless the matter was highly damaging (State v. Clow).

Issues for each side: Prosecutors can rely on the research to show that a correction, a rationale for an exclusion ruling, and a record of a witness’s first account limit the effect, but should not treat a repeated account as a corroborated one. Defense counsel can show that repetition raises belief and confidence without adding evidence, but should not claim that any repeated allegation is for that reason false.

People tend to believe a statement more after they have encountered it before. This tendency, called the illusion-of-truth effect (or the illusory truth effect, or simply the truth effect), does not depend on new evidence or argument: a second or third exposure to the same claim is enough to raise its perceived truth. It operates for true and false statements alike.

Repetition is common in the legal process. An allegation may be reported in the news, told by a witness to several listeners and interviewers, restated in reports, and repeated by counsel in argument, and jurors are told to disregard what they heard outside the courtroom and to set aside stricken testimony. The research bears on each of these settings, and equally on claims that favor either side.

This paper describes the finding and its size, its explanation, the role of knowledge and accuracy goals, what the research shows about corrections, and how repetition affects witnesses’ reports, followed by the limits of the evidence and the governing federal, military, and Arizona law.

The Finding and Its Size

In the first study of the effect, participants rated their confidence that each of 60 plausible statements on obscure topics was true, in three sessions two weeks apart; some statements were repeated across sessions and others were new each time (Hasher et al., 1977). Perceived truth of the repeated statements rose across sessions, whether the statements were actually true or false, while the new statements showed no such rise. A meta-analysis of 51 studies confirmed that the effect is reliable, and found that it is larger when repeated statements are compared with new ones than when a single statement’s ratings are compared before and after repetition (Dechêne et al., 2010).

A systematic review and meta-analysis published in 2026 updated the evidence with 182 studies, 366 effect sizes, and 31,184 participants published from 1977 to 2025 (Ye et al., 2026). After correcting for small-study effects, the authors described the effect as small (Hedges’ g = 0.37), with substantial variation within and between studies. Variables that accounted for that variation included the type of statement, the instructions given at first exposure, whether cues about truth or falsity were present, and how long the statement was shown the first time. The Implicit Memory paper discusses the same meta-analysis in connection with familiarity-based errors.

Several features of the effect are relevant to legal settings. The largest increase in perceived truth comes from the second encounter, with smaller increases for each further repetition; in two experiments that showed statements up to 27 times, the increase was logarithmic (Hassan & Barber, 2021). The effect has been found after delays ranging from minutes to a month, although in a preregistered longitudinal study it was smaller at longer delays (Henderson et al., 2021). Repetition raised belief even in highly implausible statements, although by smaller absolute amounts than for ambiguous ones (Fazio et al., 2019; Lacassagne et al., 2022). A review in 2024 noted that repetition also increases belief in fake news headlines and conspiracy-related claims, and can make an unethical act seem less unethical (Udry & Barber, 2024).

Why Repetition Increases Belief

The leading explanation is processing fluency: a previously encountered statement is processed more easily on a later encounter, and people use that ease as a cue that the statement is true (Dechêne et al., 2010; Brashier & Marsh, 2020). The cue is not irrational. In ordinary life, claims that people hear often from many sources are more often true than not, and relying on familiarity is frequently a reasonable shortcut (Hassan & Barber, 2021). The difficulty is that fluency can come from any prior exposure, including exposure to a false claim, and the feeling of familiarity does not carry information about where the claim came from or whether it was accurate.

Remembering can work in a similar way. In one set of experiments, information that participants retrieved from their own memory came to be judged as more true, suggesting that the act of recalling a claim, and not only hearing it again from others, can lend it credibility (Ozubko & Fugelsang, 2011).

Knowledge, Accuracy Goals, and Warnings

It was long assumed that people would not be affected by repetition of a claim they knew to be false. Fazio and colleagues (2015) tested that assumption and found the effect even for statements that contradicted participants’ demonstrated knowledge, such as false statements about well-known facts; modeling suggested that people sometimes relied on fluency even when the correct knowledge was available to them. The authors called this “knowledge neglect.”

Knowledge does matter, however, when people are prompted to use it. In four experiments, asking participants to rate the accuracy of each statement when they first encountered it, as a fact-checker would, eliminated the later illusion, but only for statements about which participants had relevant knowledge, and the benefit persisted over a delay (Brashier et al., 2020). Reviews have also identified instructions to focus on accuracy and awareness of the effect as interventions that reduce its size (Udry & Barber, 2024). The 2026 meta-analysis likewise found that first-exposure instructions and veracity cues were among the variables associated with the size of the effect (Ye et al., 2026). The effect is robust enough to appear when people know better, and weaker when they evaluate a claim’s accuracy when they first hear it.

Corrections, Denials, and Instructions to Disregard

A concern in the earlier literature was that repeating a false claim in order to correct it could make it more familiar and therefore more believed. In two experiments with consumer claims, repeatedly telling participants that a claim was false helped older adults recall it correctly soon afterward but made them more likely to misremember it as true after a three-day delay (Skurnik et al., 2005). Later research has generally not supported a broad claim that corrections backfire. A review of the backfire literature, including familiarity backfire, concluded that backfire effects are not a robust empirical phenomenon and that apparent instances often reflect measurement problems (Swire-Thompson et al., 2020). In three experiments with 1,718 participants, corrections that exposed people to entirely new misinformation did not leave them with stronger misconceptions than a control group never exposed to the claims, even after a week (Ecker et al., 2020). Corrections do not, however, fully undo exposure: a review of misinformation research described a “continued influence” in which corrected information still affects later reasoning to some degree (Ecker et al., 2022).

Research on juries points the same way. A meta-analysis of 48 studies with 8,474 participants found that inadmissible evidence had a reliable effect on mock-juror verdicts and that an instruction to disregard it did not eliminate that effect; compliance improved when the judge gave a reason for the ruling, and contested evidence that was ruled admissible had heightened impact (Steblay et al., 2006). A meta-analysis of pretrial publicity found that participants exposed to negative publicity about a defendant were more likely to judge the defendant guilty, with a modest average effect (Steblay et al., 1999). Neither meta-analysis isolated repetition as such; they show that information jurors are told to set aside can still influence them, which is consistent with, but not a direct test of, the illusion-of-truth account.

Repetition and Witness Reports

Repetition also affects what witnesses report about events they observed. In a misinformation study, participants who watched a video of a crime and then read eyewitness reports were more likely to adopt misleading details, and were more confident in them, when the details were repeated, whether the repetitions came from one eyewitness or from three (Foster et al., 2012). The number of times a claim was heard mattered more than the number of people who made it. Repeated exposure to suggested details also increased the likelihood that participants later reported remembering them from the event itself (Zaragoza & Mitchell, 1996), and repeated postevent questioning increased witnesses’ confidence in their answers without a corresponding increase in accuracy (Shaw & McClure, 1996).

These findings do not mean that a repeated or retold account is unreliable. Repetition increases belief in true information as well as false information. Accuracy-focused retelling can strengthen recall; slanted retelling, repeated suggestive questioning, or exposure to others’ accounts can contaminate it (see “Remembering Changes Memory”). A witness who tells an accurate account many times is repeating accurate content, and in non-suggestive mock-crime studies well-conducted repeated interviews produced new details that were often accurate, as the Remembering Changes Memory paper in this hub describes. The practical point is narrower: repetition can raise confidence and a sense of truth without adding evidence, so the confidence of a witness, or of a listener, after many retellings is not itself a measure of accuracy. What matters is the content of the earliest documented account and what the witness was exposed to afterward.

Limits of the Evidence

Most illusion-of-truth studies use trivia statements, headlines, or invented claims rated by university students or online participants on a truth scale, with low stakes and short exposures. The average effect is small and heterogeneous (Ye et al., 2026), and a shift on a rating scale is not the same as a change in a verdict, a sworn account, or a decision about guilt. Very few studies test repetition with trial materials, and none identified here tests repetition across a full trial with deliberation. The backfire findings for corrections rest heavily on older adults in a single study (Skurnik et al., 2005), and larger later studies did not find that corrections generally backfire (Ecker et al., 2020). Jury studies on inadmissible evidence and publicity show influence that persists despite instructions but do not isolate repetition. Above all, group research shows how repetition tends to affect belief on average; it cannot show that repetition caused a particular witness to believe something false or that a particular juror was persuaded by familiarity rather than evidence.

Questions to Ask About This Research

When the 2026 meta-analysis is cited to show that repetition makes claims seem true, counsel should ask how large the effect is in absolute terms and what was measured: the authors describe the corrected average as small (g = 0.37) with substantial heterogeneity, and the outcome was a truth rating of statements, not a judgment about a person or an event (Ye et al., 2026). When Skurnik et al. (2005) is offered to argue that a curative instruction or a repeated denial will entrench a claim, counsel should ask which participants showed the effect and under what conditions, because the backfire appeared in older adults after a three-day delay and later, larger studies found that corrections generally reduce belief (Ecker et al., 2020; Swire-Thompson et al., 2020). When Fazio et al. (2015) is used to say that jurors cannot resist repetition even when they know better, counsel should ask whether the participants were asked to evaluate accuracy at first exposure, since doing so reduced the effect for claims about which they had relevant knowledge (Brashier et al., 2020). When Foster et al. (2012) is cited, counsel should ask whether there is evidence that this witness was in fact exposed to the repeated detail before giving the account. These questions are explained in “Reading Research Claims: A Guide for Attorneys” on this site.

The Illusion-of-Truth Effect and the Law

Federal and Military Standards

Expert testimony about the effect of repetition on belief and memory is governed by Federal Rule of Evidence 702, as amended December 1, 2023, under which the proponent must show the court that it is more likely than not that the rule’s requirements are met, including that the opinion reflects a reliable application of reliable methods to the case. Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) made the trial judge a gatekeeper, and Kumho Tire Co. v. Carmichael (1999) extended that obligation to all expert testimony, including testimony based on technical or other specialized knowledge. In courts-martial, Military Rule of Evidence 702 tracks the federal rule, the 2023 federal amendment took effect in the military rule in 2025 through Military Rule of Evidence 1102 (Joint Service Committee on Military Justice, 2025), and practitioners should confirm current text; military judges apply the six factors of United States v. Houser (1993). Such testimony is general: it can explain how repetition affects belief and confidence, but it cannot tell the factfinder whether a particular claim is true.

The law generally presumes that jurors follow their instructions (Richardson v. Marsh, 1987), and limiting instructions and the exclusion of unfairly prejudicial evidence are provided for in Rules 105 and 403 of both the Federal and Military Rules of Evidence. The Supreme Court has also recognized that in some contexts the risk that jurors will not or cannot follow an instruction is too great to rely on it (Bruton v. United States, 1968), and Justice Jackson described the assumption that instructions can overcome prejudicial effects as one that “all practicing lawyers know to be unmitigated fiction” (Krulewitch v. United States, 1949, Jackson, J., concurring). When pretrial publicity is extensive, the usual remedies are careful voir dire, continuance, and change of venue; the Supreme Court has presumed prejudice from publicity only in extreme cases (Skilling v. United States, 2010). In courts-martial, the place of trial may be changed when necessary to prevent prejudice to the rights of the accused (R.C.M. 906(b)(11)).

Arizona

Arizona Rule of Evidence 702 adopted the federal formulation and the Daubert standard effective January 1, 2012, and was amended effective January 1, 2024, to conform to the 2023 federal amendment (Ariz. Sup. Ct. Order R-23-0004). State v. Chapple (1983) is Arizona’s leading case on expert testimony about memory and eyewitness reliability; excluding such testimony was an abuse of discretion on its facts, while admission otherwise remains within the trial court’s discretion (State v. Nordstrom, 2001). General, educational testimony that satisfies Rule 702 and Rule 403 is permitted (State v. Salazar-Mercado, 2014), but an expert may not opine on whether a particular witness is truthful (State v. Lindsey, 1986, 149 Ariz. at 475). Arizona’s standard instructions tell jurors that what the lawyers say in opening statements and closing arguments is not evidence (RAJI (Criminal) Standard Criminal 10) and that they must disregard questions to which objections were sustained and testimony that was stricken (Standard Criminal 8). The comment to Standard Criminal 8 notes that an admonition to disregard an improper comment is generally sufficient to cure its prejudicial impact unless the matter was highly damaging or the instruction clearly inadequate (State v. Clow, 1981).

Special Issues in Legal Practice

The principles described above apply with equal force to every party in a legal proceeding. The science operates the same way regardless of who is asking the questions, and the research summarized here does not by itself favor either side. What differs between the parties is not the science but the vantage point — the particular places where these issues tend to surface, and the particular errors each party is best positioned to guard against. The two summaries below identify those recurring issues. They are offered for orientation, not as litigation strategy; in every case the controlling question is what the evidence in that case will, and will not, support, and the expert’s role is to inform the trier of fact rather than to advocate for either side.

Special Issues for Prosecutors

The research supports several propositions prosecutors can legitimately present. Repetition increases belief in true statements as well as false ones, so the fact that a complainant or witness has told an account several times does not by itself suggest that the account is inaccurate, and repeated, well-conducted interviews can yield accurate new detail. Recent research does not support the view that a correction generally strengthens the claim it corrects, and the jury research indicates that a judge’s explanation of why evidence is excluded may improve compliance with an instruction to disregard (Steblay et al., 2006). Prosecutors are well positioned to limit the effect where it matters: by recording a witness’s first account before repeated retellings, documenting what information was shared with the witness, avoiding repetition of details to witnesses during interviews, and asking the court to state reasons when evidence is excluded.

The research also counsels caution. A witness’s confidence can rise with repeated retelling and questioning without any gain in accuracy, so growing certainty is not corroboration. Repetition of an allegation across reports, interviews, and media accounts adds familiarity but, by itself, no independent evidence; whether several reports trace to one source is a factual question for the case (see Foster et al., 2012, a study of adoption of misleading details after a crime video). Arguments by either side that restate a contested claim, rather than pointing to its evidence, draw on the mechanism this research describes.

Special Issues for Defense

The research supports several propositions defense counsel can legitimately present. Repetition raises perceived truth on average, even for some claims that contradict what people know, though the effect is weaker when people evaluate accuracy at first exposure, and repeated misleading details increase both their adoption into witness reports and witnesses’ confidence in them. Instructions to disregard do not fully eliminate the influence of inadmissible evidence, and negative pretrial publicity is associated with more guilty judgments in mock-juror research. Expert testimony explaining these general principles, combined with evidence of what a witness actually heard and how often, is a legitimate way to help the factfinder weigh an account or a claim on its evidentiary support rather than its familiarity.

The research also counsels caution about its limits. The average effect is small, it was measured with truth ratings of statements rather than verdicts, and it cannot show that a particular allegation is false or that particular jurors were persuaded by familiarity. The strong form of the backfire claim, that a correction or curative instruction will entrench a claim, rests on limited evidence and is not supported by larger later studies, and the research does not support the claim that a correction generally entrenches the claim it corrects. The same principles apply to the accused: a defendant’s or defense witness’s account told repeatedly, and repeated in argument, gains familiarity in the same way, and the research does not favor either party’s repeated themes.

This paper is for educational purposes only and is not legal advice. The author is a psychologist, not an attorney; summaries of law are general and must be verified against current authority or with a licensed attorney.

References

Brashier, N. M., Eliseev, E. D., & Marsh, E. J. (2020). An initial accuracy focus prevents illusory truth. Cognition, 194, Article 104054. https://doi.org/10.1016/j.cognition.2019.104054

Brashier, N. M., & Marsh, E. J. (2020). Judging truth. Annual Review of Psychology, 71, 499–515. https://doi.org/10.1146/annurev-psych-010419-050807

Dechêne, A., Stahl, C., Hansen, J., & Wänke, M. (2010). The truth about the truth: A meta-analytic review of the truth effect. Personality and Social Psychology Review, 14(2), 238–257. https://doi.org/10.1177/1088868309352251

Ecker, U. K. H., Lewandowsky, S., & Chadwick, M. (2020). Can corrections spread misinformation to new audiences? Testing for the elusive familiarity backfire effect. Cognitive Research: Principles and Implications, 5, Article 41. https://doi.org/10.1186/s41235-020-00241-6

Ecker, U. K. H., Lewandowsky, S., Cook, J., Schmid, P., Fazio, L. K., Brashier, N., Kendeou, P., Vraga, E. K., & Amazeen, M. A. (2022). The psychological drivers of misinformation belief and its resistance to correction. Nature Reviews Psychology, 1(1), 13–29. https://doi.org/10.1038/s44159-021-00006-y

Fazio, L. K., Brashier, N. M., Payne, B. K., & Marsh, E. J. (2015). Knowledge does not protect against illusory truth. Journal of Experimental Psychology: General, 144(5), 993–1002. https://doi.org/10.1037/xge0000098

Fazio, L. K., Rand, D. G., & Pennycook, G. (2019). Repetition increases perceived truth equally for plausible and implausible statements. Psychonomic Bulletin & Review, 26(5), 1705–1710. https://doi.org/10.3758/s13423-019-01651-4

Foster, J. L., Huthwaite, T., Yesberg, J. A., Garry, M., & Loftus, E. F. (2012). Repetition, not number of sources, increases both susceptibility to misinformation and confidence in the accuracy of eyewitnesses. Acta Psychologica, 139(2), 320–326. https://doi.org/10.1016/j.actpsy.2011.12.004

Hasher, L., Goldstein, D., & Toppino, T. (1977). Frequency and the conference of referential validity. Journal of Verbal Learning and Verbal Behavior, 16(1), 107–112. https://doi.org/10.1016/S0022-5371(77)80012-1

Hassan, A., & Barber, S. J. (2021). The effects of repetition frequency on the illusory truth effect. Cognitive Research: Principles and Implications, 6, Article 38. https://doi.org/10.1186/s41235-021-00301-5

Henderson, E. L., Simons, D. J., & Barr, D. J. (2021). The trajectory of truth: A longitudinal study of the illusory truth effect. Journal of Cognition, 4(1), Article 29. https://doi.org/10.5334/joc.161

Joint Service Committee on Military Justice. (2025). Amendments to the Military Rules of Evidence since 1984 (G. E. Maggs, Ed.; 2025 ed.). https://jsc.defense.gov/Portals/99/MRE%20Amendments%202025.pdf

Lacassagne, D., Béna, J., & Corneille, O. (2022). Is Earth a perfect square? Repetition increases the perceived truth of highly implausible statements. Cognition, 223, Article 105052. https://doi.org/10.1016/j.cognition.2022.105052

Ozubko, J. D., & Fugelsang, J. (2011). Remembering makes evidence compelling: Retrieval from memory can give rise to the illusion of truth. Journal of Experimental Psychology: Learning, Memory, and Cognition, 37(1), 270–276. https://doi.org/10.1037/a0021323

Shaw, J. S., & McClure, K. A. (1996). Repeated postevent questioning can lead to elevated levels of eyewitness confidence. Law and Human Behavior, 20(6), 629–653. https://doi.org/10.1007/BF01499235

Skurnik, I., Yoon, C., Park, D. C., & Schwarz, N. (2005). How warnings about false claims become recommendations. Journal of Consumer Research, 31(4), 713–724. https://doi.org/10.1086/426605

Steblay, N., Hosch, H. M., Culhane, S. E., & McWethy, A. (2006). The impact on juror verdicts of judicial instruction to disregard inadmissible evidence: A meta-analysis. Law and Human Behavior, 30(4), 469–492. https://doi.org/10.1007/s10979-006-9039-7

Steblay, N. M., Besirevic, J., Fulero, S. M., & Jimenez-Lorente, B. (1999). The effects of pretrial publicity on juror verdicts: A meta-analytic review. Law and Human Behavior, 23(2), 219–235. https://doi.org/10.1023/A:1022325019080

Swire-Thompson, B., DeGutis, J., & Lazer, D. (2020). Searching for the backfire effect: Measurement and design considerations. Journal of Applied Research in Memory and Cognition, 9(3), 286–299. https://doi.org/10.1016/j.jarmac.2020.06.006

Udry, J., & Barber, S. J. (2024). The illusory truth effect: A review of how repetition increases belief in misinformation. Current Opinion in Psychology, 56, Article 101736. https://doi.org/10.1016/j.copsyc.2023.101736

Ye, S., Attali, D., Ghazi, M., Cachia, A., Cassotti, M., & Borst, G. (2026). Systematic review and meta-analysis of the evidence for an illusory truth effect and its determinants. Nature Communications, 17, Article 3270. https://doi.org/10.1038/s41467-026-70041-x

Zaragoza, M. S., & Mitchell, K. J. (1996). Repeated exposure to suggestion and the creation of false memories. Psychological Science, 7(5), 294–300. https://doi.org/10.1111/j.1467-9280.1996.tb00377.x

Legal Authorities

Bruton v. United States, 391 U.S. 123 (1968).

Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).

Krulewitch v. United States, 336 U.S. 440 (1949).

Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999).

Richardson v. Marsh, 481 U.S. 200 (1987).

Skilling v. United States, 561 U.S. 358 (2010).

State v. Chapple, 135 Ariz. 281, 660 P.2d 1208 (1983).

State v. Clow, 130 Ariz. 125 (1981).

State v. Lindsey, 149 Ariz. 472, 720 P.2d 73 (1986).

State v. Nordstrom, 200 Ariz. 229, 25 P.3d 717 (2001).

State v. Salazar-Mercado, 234 Ariz. 590, 325 P.3d 996 (2014).

United States v. Houser, 36 M.J. 392 (C.M.A. 1993).

Fed. R. Evid. 105.

Fed. R. Evid. 403.

Fed. R. Evid. 702.

Mil. R. Evid. 105.

Mil. R. Evid. 403.

Mil. R. Evid. 702.

Mil. R. Evid. 1102.

Rule for Courts-Martial 906(b)(11).

Ariz. R. Evid. 702.

Ariz. Sup. Ct. Order R-23-0004 (amending Ariz. R. Evid. 702, effective Jan. 1, 2024).

Revised Arizona Jury Instructions (Criminal), Standard Criminal 8 (Evidence to Be Considered) and Standard Criminal 10 (Lawyers’ Comments Are Not Evidence) (6th ed. 2022).

Related topics from Arizona Forensic Services: False Confessions: Suggestibility · Courts-Martial