Episodic Memory
Illusory Truth Task
Also called: illusory truth effect task, truth effect paradigm, repetition-induced truth effect, repeated statements truth task
Measure the illusory truth effect: trivia statements read once before are rated as more true than new ones, false statements included.
8-11 minUntimed
Free to start: 10 free participants per account, then $0.99 per participant for academic research, or any yearly plan. Try it here first, with no account.
- Papers, 2021 to 2025
- 224
- Evidence grade
- C
- Registered clinical studies
- 0
What it measures
Measures the illusory truth effect: statements read once before seem more true. Participants rate trivia statements about nature and science for how interesting they are, then rate how true they are among new ones; half are false. The main score is the truth boost: mean truth rating of repeated statements minus new ones. The last screen names the false statements and their corrections.
Constructs
- Illusory truth effect
- Processing fluency
- Truth judgment
- Memory for statements
Research uses
- Misinformation and belief research
- Memory and judgment research
- Within-study comparison of groups and conditions
How the paradigm works
The Illusory Truth Task measures the illusory truth effect: a statement read once before seems more true than a new one. The effect was first reported by Hasher, Goldstein and Toppino (1977), with repetitions weeks apart; most later studies run it in a single session, as here (Henderson, Westwood and Simons 2022). Participants first read 24 short statements about nature and science, one at a time, and rate how interesting each one is from 1 (not interesting) to 6 (very interesting), with nothing said about truth. After 60 seconds of true-or-false arithmetic (0 to 180 as a setting), they rate how true each of 48 statements is, from 1 (definitely false) to 6 (definitely true): the 24 they read before mixed with 24 new ones, with no more than 3 of either kind in a row. Half of each kind are true. Both ratings are untimed. A shorter form shows 32 statements, 16 of them read first.
More about the paradigm
The statements were written for this task: trivia about space, physics, chemistry, animals and plants whose truth does not depend on where a person lives, with no statement about health, politics or groups of people. Each false statement gets one fact wrong, and each statement's truth was checked against a public source named in the stimulus file. The session's seed draws which statements are read first, so across sessions every statement is repeated and new equally often. The statements are written in each of the app's eight languages. Rating interest first makes people read each statement without judging its truth: Brashier, Eliseev and Marsh (2020) found that judging truth at first reading removed the later effect when people knew the facts. The last screen says that half the statements were false and lists each false one with the correct fact.
The primary score is the truth boost: the mean truth rating of the repeated statements minus that of the new ones, in scale points. Scores also give the boost among true and among false statements, the share of each kind rated on the true half of the scale, the difference between the ratings of true and false statements, which shows how far ratings follow the facts, and the interest ratings. In Henderson, Simons and Barr's (2021) registered study, on a 7-point scale, repeated statements were rated 0.67 points truer than new ones when tested right after the first reading, and 75% of participants rated repeated statements higher; across the 17 studies with 6- or 7-point scales that they reviewed, the difference ranged from 0.13 to 1.30 points, with a mean of 0.45. A second session would show every statement again after the corrections, so the test is meant to be taken once by each person, and a repeat session is flagged. Scores describe how an earlier reading changes truth ratings in this task, a research measure; they do not diagnose.
Scores
- Truth Boostpoints
- Mean truth rating of the statements read before minus that of the new statements, on the scale from 1 to 6.
- Positive means repeated statements were rated truer
- Truth Rating, Repeatedpoints
- Mean truth rating of the statements read before, from 1 (definitely false) to 6 (definitely true).
- Compare with the new statements
- Truth Rating, Newpoints
- Mean truth rating of the statements not read before.
- The baseline
- Truth Boost, True Statementspoints
- The truth boost among the true statements only.
- Context for the truth boost
- Truth Boost, False Statementspoints
- The truth boost among the false statements only.
- Positive means repetition made false statements seem truer
- Rated True, Repeated%
- Share of the statements read before rated 4, 5 or 6.
- Compare with the new statements
- Rated True, New%
- Share of the new statements rated 4, 5 or 6.
- The baseline
- True Minus Falsepoints
- Mean truth rating of the true statements minus that of the false ones, over all statements.
- Higher means ratings followed the facts more closely
- Mean Interest Ratingpoints
- Mean interest rating in the first phase, from 1 to 6.
- Context for the first phase
- Interest Ratingscount
- Statements rated for interest in the first phase.
- Context for the first phase
- Statements Rated for Truthcount
- Truth ratings in the scored run.
- Fewer than 90% of those planned is invalid
- Statements Plannedcount
- Statements the session set out to rate for truth.
- 32 or 48
- Scale Points Usedcount
- How many of the six scale points the truth ratings used.
- 1 means the same rating throughout, which is invalid
- Median Truth Rating Timems
- Median time to rate a statement for truth, leaving out ratings under 100 ms.
- Context for the ratings
- Median Interest Rating Timems
- Median time to rate a statement for interest, leaving out ratings under 100 ms.
- Under 200 ms is flagged for review
- Ratings Under 100 mscount
- Truth ratings given within 100 ms of the statement. They still count as ratings.
- Expected to be 0
- Delayseconds
- Seconds of arithmetic between the two phases.
- Setting context
- Earlier Sessionscount
- This participant's earlier sessions of the task, when scoring counted them.
- Above 0 is flagged for review
Use and evidence
224 papers from 2021 to 2025 name this task in their title or abstract, up 113% compared with 2016 to 2020. That ranks it 127 of 495 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 81 |
| 2024 | 47 |
| 2023 | 45 |
| 2022 | 26 |
| 2021 | 25 |
| 2020 | 30 |
| 2019 | 36 |
| 2018 | 13 |
| 2017 | 15 |
| 2016 | 11 |
| 2015 | 7 |
| 2014 | 7 |
| 2013 | 10 |
| 2012 | 4 |
| 2011 | 7 |
| 2010 | 6 |
| 2009 | 7 |
| 2008 | 3 |
| 2007 | 5 |
| 2006 | 3 |
| 2005 | 3 |
| 2004 | 4 |
| 2003 | 1 |
| 2002 | 4 |
| 2001 | 0 |
| 2000 | 0 |
Use grade C
100 to 299 papers from 2021 to 2025.
Evidence grade C
At least 2 test-retest papers, 30 reliability or validity papers or 3 registered clinical studies.
- Papers on test-retest reliability
- 3
- Papers on reliability or validity
- 44
- Registered clinical studies using it as an outcome
- 0
How the grades work
Use: A is 1,000 or more papers from 2021 to 2025, B 300 to 999, C 100 to 299, D 30 to 99 and E fewer than 30. Evidence: A means at least 25 papers report its test-retest reliability and at least 25 registered clinical studies use it as an outcome; B, at least 8 test-retest papers, and either 5 registered clinical studies or 150 reliability or validity papers; C, at least 2 test-retest papers, 30 reliability or validity papers or 3 registered clinical studies; D, little published measurement evidence found. The counts measure use. They include every paper that names the task in its title or abstract. Grades describe the published research on this task, not ConductCognition's version of it.
Source: ConductCognition test census 0.22.0, counted 3 November 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Statements
- 48 trivia statements written for this task, 24 true and 24 false, about space, physics, chemistry, animals and plants, with no health, political or group claims. Each statement's truth was checked against a public source. The statements are in the session's language.
- First phase
- 24 statements by default, or 16 with the 32-statement setting, each rated for interest from 1 to 6 with no time limit. Half are true, with no more than 3 true or false in a row. Nothing is said about truth.
- Delay
- 60 seconds of true-or-false arithmetic by default, 0 to 180 as a setting.
- Truth ratings
- Every statement read first, mixed with as many new ones, each rated from 1 (definitely false) to 6 (definitely true) with no time limit and no more than 3 repeated or new in a row. The session's seed draws which statements are read first.
- Last screen
- Says that half the statements were false and lists each false one with the correct fact.
- Score
- Truth boost: the mean truth rating of the repeated statements minus that of the new ones, in scale points.
The statements and corrections were written for this task; no published statement set is used. A second session would repeat every statement after its correction, so each person takes the task once, and a repeat session is flagged.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: illusory_truth_test from the scored run, one truth rating from 1 to 6 per statement, untimed, with the interest ratings from the same run. A rating is a judgment with no correct option, so accuracy is not judged against chance. The same rating on every statement invalidates, and so do fewer than 90% of the planned statements rated. Ratings under 200 ms on at least half of 4 or more statements invalidate. Interest ratings with a median time under 200 ms and an earlier session of this test are flagged for review. A hidden tab withholds the percentile.
Why these rules
There is no correct option to compare with chance, so accuracy is not judged against chance. Henderson, Simons and Barr (2021) excluded participants who gave every statement the same rating, because such ratings cannot depend on the statements. The score compares two halves of the statements, so it needs nearly all of them; the 90% limit is a ConductScience choice. Statements rated for interest faster than a visual reaction were probably not read, and an unread statement is not repeated. Every statement of a second session has been read before and its truth told at the end of the first, so an earlier session is flagged. An answer under 200 ms is faster than a simple visual reaction, so it cannot reflect the item. Following response-time effort screening for untimed tests (Wise and Kong 2005), the session is invalid only when at least half the answers are that fast. A hidden tab lets the study, delay or response timers run without the participant, so a percentile is withheld after one.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Statements | 48 statements (24 rated first, standard) | 32 statements (16 rated first), 48 statements (24 rated first, standard) |
| Delay before the truth ratings (seconds) | 60 | 0 to 180 |
Yearly plans can change settings within these limits. Free and pay-as-you-go studies use the standard settings.
Need a setting this test does not have?
Devices and languages
- Untimed test: runs on desktops, laptops, tablets and phones. Participant devices
- Languages: English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese.
- Available on: Every plan, including the free plan.
- No percentile. Scores and quality flags only. How norms work
- Recruiting online? See the setup guides for Prolific, Sona Systems, CloudResearch Connect and Qualtrics.
Cite and describe
Participants completed the Illusory Truth Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Hasher, Goldstein & Toppino, 1977; Henderson, Simons & Barr, 2021), with the standard settings (statements: 48 statements (24 rated first, standard); delay before the truth ratings (seconds): 60). The main score was truth boost (mean truth rating of the statements read before minus that of the new statements, on the scale from 1 to 6).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- 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
- 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), 29. https://doi.org/10.5334/joc.161Truth ratings right after a first reading, the size of the effect and the exclusion of uniform ratings.
- Henderson, E. L., Westwood, S. J., & Simons, D. J. (2022). A reproducible systematic map of research on the illusory truth effect. Psychonomic Bulletin & Review, 29(3), 1065-1088. https://doi.org/10.3758/s13423-021-01995-wThe single-session design most studies use.
- Brashier, N. M., Eliseev, E. D., & Marsh, E. J. (2020). An initial accuracy focus prevents illusory truth. Cognition, 194, 104054. https://doi.org/10.1016/j.cognition.2019.104054Why the first phase asks for interest, not truth.
Source papers
- 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.Paradigm source, Adults
- Henderson EL, Simons DJ, Barr DJ (2021). The trajectory of truth: a longitudinal study of the illusory truth effect. Journal of Cognition, 4(1):29.Paradigm source, Adults 18 to 65, United Kingdom
- Henderson EL, Westwood SJ, Simons DJ (2022). A reproducible systematic map of research on the illusory truth effect. Psychonomic Bulletin & Review, 29(3):1065-1088.Paradigm source, Mixed
- Brashier NM, Eliseev ED, Marsh EJ (2020). An initial accuracy focus prevents illusory truth. Cognition, 194:104054.Paradigm source, Adults
Questions
How long does the Illusory Truth Task take?
About 8 to 11 minutes, as listed in the test library.
What device does a participant need?
Untimed test: runs on desktops, laptops, tablets and phones. The browser must be Chrome, Edge, Firefox or Safari.
What scores does it produce?
Truth Boost, Truth Rating, Repeated, Truth Rating, New, Truth Boost, True Statements, Truth Boost, False Statements, Rated True, Repeated, Rated True, New, True Minus False, Mean Interest Rating, Interest Ratings, Statements Rated for Truth, Statements Planned, Scale Points Used, Median Truth Rating Time, Median Interest Rating Time, Ratings Under 100 ms, Delay and Earlier Sessions. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Illusory Truth Task used in research?
224 papers from 2021 to 2025 name it in their title or abstract, up 113% compared with 2016 to 2020. That ranks it 127 of 495 test families in the ConductCognition test census (use grade C). Source: ConductCognition test census 0.22.0, counted 3 November 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Illusory Truth Task have?
In the published research, 3 papers report its test-retest reliability and 0 registered clinical studies use it as an outcome (evidence grade C in the ConductCognition test census).
Does it report a percentile?
No. Scores and quality flags only.
Which settings can a researcher change?
Statements (32 statements (16 rated first), 48 statements (24 rated first, standard)) and delay before the truth ratings (seconds) (0 to 180). Settings can be changed on yearly plans; free and pay-as-you-go studies use the standard settings.
Which languages can participants use?
Participants can take this test in English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese, with its words in the same language. English is on every plan, and the other languages come with yearly plans. Have a native speaker read the machine-translated text before launch.
Is this a clinical test?
No. ConductCognition is for research use only. It runs, scores and exports the test; clinical interpretation is outside the platform.
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