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Thursday, August 22, 2019

Repetition increases perceived truth equally for plausible and implausible statements

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


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.