The Trajectory of Truth: A Longitudinal Study of the Illusory Truth Effect

Henderson, E. L., Simons, D. J., & Barr, D. J.

(2021). Journal of Cognition, 4(1), 29.

DOI: http://doi.org/10.5334/joc.161

Abstract

Repeated statements are rated as subjectively truer than comparable new statements, even though repetition alone provides no new, probative information (the illusory truth effect). Contrary to some theoretical predictions, the illusory truth effect seems to be similar in magnitude for repetitions occurring after minutes or weeks. This Registered Report describes a longitudinal investigation of the illusory truth effect (n = 608, n = 567 analysed) in which we systematically manipulated intersession interval (immediately, one day, one week, and one month) in order to test whether the illusory truth effect is immune to time. Both our hypotheses were supported: We observed an illusory truth effect at all four intervals (overall effect: χ2(1) = 169.91; M(repeated) = 4.52, M(new) = 4.14; H1), with the effect diminishing as delay increased (H2). False information repeated over short timescales might have a greater effect on truth judgements than repetitions over longer timescales. Researchers should consider the implications of the choice of intersession interval when designing future illusory truth effect research.

Discussion

We used a repeated measures, longitudinal design to investigate the trajectory of the illusory truth effect over time: immediately, one day, one week, and one month. Both of our hypotheses were supported: We observed a main effect of the illusory truth effect when averaging across all four delay conditions (H1). The illusory truth effect was present at all four intervals, but the size of the effect diminished as the interval duration increased (H2). The repeated-minus-new difference was largest when tested immediately (0.67) and shrank after one day (0.39), one week (0.27), and one month (0.14). This reduction in the illusory truth effect over time is inconsistent with an earlier meta-analysis that found no relationship between the size of the effect and intersession interval across studies (Dechêne et al., 2010), but it is consistent with one between-subjects study showing a smaller effect after one week than after a few minutes (Silva et al., 2017, Experiment 1).

The reduced effect after a delay is consistent with the recognition, familiarity, and processing fluency explanations of the illusory truth effect. All three explanations predict larger effects for recently repeated items and smaller effects as feelings of recognition, familiarity or fluency fade with time.

A caveat to the processing fluency account occurs when the source of fluency is obvious (e.g., when participants recognise that statements have been recently repeated). In such cases, participants might not use processing fluency to make their judgments of truth, thereby eliminating the effect (Alter & Oppenheimer, 2009; Nadarevic & Erdfelder, 2014; Oppenheimer, 2004). Our results challenge this fluency discounting explanation because the size of the illusory truth effect was greatest when tested immediately, when participants should be most aware that some statements had been repeated. Similarly, the source disassociation hypothesis predicts that the illusory truth effect should increase with time as people forget that they saw the statements during the experiment, remembering only the semantic content and attributing it to a source outside the experiment. Here we find the opposite.

The research is here.

Repetition increases perceived truth equally for plausible and implausible statements

Lisa Fazio David Rand Gordon Pennycook
PsyArXiv
Originally created February 28, 2019

Abstract

Repetition increases the likelihood that a statement will be judged as true. This illusory truth effect is well-established; however, it has been argued that repetition will not affect belief in unambiguous statements. When individuals are faced with obviously true or false statements, repetition should have no impact. We report a simulation study and a preregistered experiment that investigate this idea. Contrary to many intuitions, our results suggest that belief in all statements is increased by repetition. The observed illusory truth effect is largest for ambiguous items, but this can be explained by the psychometric properties of the task, rather than an underlying psychological mechanism that blocks the impact of repetition for implausible items. Our results indicate that the illusory truth effect is highly robust and occurs across all levels of plausibility. Therefore, even highly implausible statements will become more plausible with enough repetition.

The research is here.

The conclusion:

In conclusion, our findings are consistent with the hypothesis that repetition increases belief in all statements equally, regardless of their plausibility. However, there is an important difference between this internal mechanism (equal increase across plausibility) and the observable effect. The observable effect of repetition on truth ratings is greatest for items near the midpoint of perceived truth, and small or nonexistent for items at the extremes. While repetition effects are difficult to observe for very high and very low levels of perceived truth, our results suggest that repetition increases participants’ internal representation of truth equally for all statements. These findings have large implications for daily life where people are often repeatedly exposed to both plausible and implausible falsehoods. Even implausible falsehoods may slowly become more plausible with repetition.

Truth by Repetition: Explanations and Implications

Unkelbach, C., Koch, A., Silva, R. R., & Garcia-Marques, T. (2019).
Current Directions in Psychological Science, 28(3), 247–253. https://doi.org/10.1177/0963721419827854

Abstract

People believe repeated information more than novel information; they show a repetition-induced truth effect. In a world of “alternative facts,” “fake news,” and strategic information management, understanding this effect is highly important. We first review explanations of the effect based on frequency, recognition, familiarity, and coherent references. On the basis of the latter explanation, we discuss the relations of these explanations. We then discuss implications of truth by repetition for the maintenance of false beliefs and ways to change potentially harmful false beliefs (e.g., “Vaccination causes autism”), illustrating that the truth-by-repetition phenomenon not only is of theoretical interest but also has immediate practical relevance.

Here is a portion of the closing section:

No matter which mental processes may underlie the repetition-induced truth effect, on a functional level, repetition increases subjective truth. The effect’s robustness may be worrisome if one considers that information nowadays is not randomly but strategically repeated. For example, the phenomenon of the “filter bubble” (Pariser, 2011) suggests that people get verbatim and paraphrased repetition only of what they already know and believe. As discussed, logically, this should not strengthen information’s subjective truth. However, as discussed above, repetition does influence subjective truth psychologically. In combination with phenomena such as selective exposure (e.g., Frey, 1986), confirmation biases (e.g., Nickerson, 1998), or failures to consider the opposite (e.g., Schul, Mayo, & Burnstein, 2004), it becomes apparent how even blatantly false information may come “to fix itself in the mind in such a way that it is accepted in the end as a demonstrated truth” (Le Bon, 1895/1996). For example, within the frame of a referential theory, filter bubbles repeat information and thereby add supporting coherent references for existing belief networks, which makes them difficult to change once they are established. Simultaneously, people should also process such information more fluently. In the studies reviewed here, statement content was mostly trivia. Yet, even for this trivia, participants evaluated contradictory information as being less true compared with novel information, even when they were explicitly told that it was 100% false (Unkelbach & Greifeneder, 2018). If one considers how many corresponding references the information that “vaccination leads to autism” may instigate for parents who must decide whether to vaccinate or not, the relevance of the truth-by-repetition phenomenon becomes apparent.

How Goodness Arises from Evolutionary Competition

By Martin A. Nowak
Big Ideas from Slate.com

Here is an excerpt:

In the human sphere, cooperation means helping each other. In some contexts cooperation can imply “being good.” And suddenly the conundrum disappears. The moral imperative of world religions and philosophical systems seems to make sense.  It simply asks us to be true to our cooperative heritage, to cooperate and not only to compete.

The evolutionary process among humans is not only genetic but also cultural. We have language. We write books, articles, and emails, come up with ideas, replicate knowledge. A group of humans learning from each other instantiate a cultural evolutionary process with mutation and selection. And cooperation.

What makes cooperation a possible strategy among humans? The answer is repetition and reputation. Most of our crucial social interactions occur repeatedly with the same people or in situations where we are known, where actions can be observed by others, and thus affect our reputation.

The entire piece is here.