Illusory truth effect

The illusory truth effect is a principle that explains the phenomenon of why people tend to believe false information after repeated exposure to it, even if they initially were able to identify the information as false. It is based on the premise that when a person assesses what they believe to be a truth, they rely on whether the information is familiar to them. Researchers have found that repetitively hearing a wrong fact can overpower rationality and cause the perception of the erroneous fact as truth, and the mind is tricked into making a false memory that it relies on to make an informed decision. In effect, it causes a person to think to themselves: “That fact sounds familiar, so it must be correct.” Research has shown this result even when a person knew a particular answer on a test was correct but chose a wrong answer after being persuaded by exposure to the repetition of the wrong answer.

The illusory truth effect is significant to the decisions people make and, as a field of study, closely ties in with advertising, news media, and political campaigns and propaganda. It adds a theoretical understanding of why people believe fake news or obvious propaganda and how people are influenced by advertising campaigns. This effect is also exemplified in social media, where bias or misinformation can be spread to large numbers of individuals and shown on feeds multiple times or by multiple accounts.

Background

Although the concept has long been understood and exploited, especially by influential politicians, the term illusory truth effect was coined in a 1977 Villanova and Temple University study. College student participants in the study were asked to decide whether a series of plausible statements sourced from trivia questions were true or false. Those statements dealt with obscure facts that the participants likely would not be familiar with. The students were given three lists, each two weeks apart. On each list were sixty statements, totaling 180 statements in all. However, twenty of the total 180 statements appeared each time on all three lists, while the other 160 statements were unique. Thus, the purpose of this was to expose the students to those twenty particular statements repetitively. After exposure to the lists, the students were presented with each statement and asked to grade their belief of its truthfulness on a scale of one to seven. The student’s average confidence in the truthfulness of the repeated statements was noticeable, which led the researchers to conclude that repeated exposure to a statement makes it appear factual without any other supporting evidence.

Similar studies have been repeated by other researchers that showed similar results. Studies usually used three or fewer repetitions of information to produce the effect, but a 2020 study used higher rates of repetition, up to twenty-seven times. The studies generally found similar results of improved recognition of truthfulness with repetition. However, the greatest increase in perceived truth occurred when encountering the same statement twice; later exposures led to only incremental increases. Conversely, studies also revealed that participants who were repetitively told a statement is false will tend to believe that statement is wrong. In addition, studies determined that repetition of false information could alter a person’s belief in information they initially knew to be true.

A study in 2014 added another facet to the study to see if it produced similar results. The researchers asked participants to judge the accuracy of statements made by people with various names. The names of the people to whom the statements were attributed also had various levels of pronunciation difficulty. The study found that the participants ranked the truthfulness higher when the statement was credited to a person with an easier-to-pronounce or more-familiar name. The conclusion was that not only the information but also the source of the information can be made more believable by making it more familiar. This is often demonstrated by advertising tactics, such as celebrity endorsements, where familiar names and faces promote a product.

Overview

People’s minds naturally follow the logic of comparing new information to what they already have identified to be true, thus using accepted truth as a touchstone for new information. Repetition of something, true or not, can skew this way of processing information to make something seem more truthful the more often a person has exposure to it. Although studies have varied the amount of repetition required for this effect, it seems that exposure to a statement just twice significantly makes the statement more believable. However, familiarity may also take the form of baseless statements consistently repeated by people in general, sometimes known as old wives’ tales.

The ability to use information to make a judgment is known as processing fluency. Swift processing fluency helps people quickly comprehend information and make everyday decisions efficiently. Processing fluency is a necessary function to allow the tens of thousands of decisions made each day to flow seamlessly and to allow people to make sense of the world around them. However, the fluency of processing something that has previously been processed without factual basis, or even as knowingly false, can be mistaken by the mind as a signal of truthfulness.

Social media, political propaganda, and advertising often rely on the illusory truth effect. Even if the instigator knows that the message will be initially identified as false or rejected at first, repetition of even obvious untruths can lead to a sizable percentage of the targeted audience eventually responding favorably. This has contributed to the rise to power of questionable politicians and the wholesale acceptance of wildly unsubstantiated commercial claims.

Other cognitive biases have been linked to the illusory truth effect, such as hindsight bias, which makes a person perceive past events more predictably and clearly after they have occurred and the full sequence of events and consequences is understood. The two effects have been linked by researchers, and the illusory truth effect is considered a type of hindsight bias. Confirmation bias, the tendency to give priority to information that confirms or supports a person’s values or existing beliefs, is also closely linked to illusory truth since both rely on the familiarity of information.

Bibliography

Hassan, Aumyo, and Sarah J. Barber. "The Effects of Repetition Frequency on the Illusory Truth Effect." Cognitive Research: Principles and Implications, vol. 6, 2021, p. 38, doi.org/10.1186/s41235-021-00301-5. Accessed 13 Dec. 2024.

Henderson, Emma, D. Simons, and D. Barr. “The Trajectory of Truth: A Longitudinal Study of the Illusory Truth Effect.” Journal of Cognition, 8 June 2021, www.journalofcognition.org/articles/10.5334/joc.161. Accessed 13 Dec. 2024.

“Illusory Truth Effect.” Psychology Today, www.psychologytoday.com/us/basics/illusory-truth-effect. Accessed 13 Dec. 2024.

“Repeating Misinformation Doesn’t Make It True, But Does Make It More Likely to Be Believed.” Association for Psychological Science, 2 Sept. 2020, www.psychologicalscience.org/news/repeating-misinformation-doesnt-make-it-true-but-does-make-it-more-likely-to-be-believed.html. Accessed 13 Dec. 2024.

Stanley, Jason. How Propaganda Works. Princeton University Press, 2015.

Udry, Jessica, et al. "The Effects of Repetition Spacing on the Illusory Truth Effect." Cognition, vol. 225, 2022, p. 105157, doi.org/10.1016/j.cognition.2022.105157. Accessed 13 Dec. 2024.

Unkelbach, Christian, and Rainer Greifeneder. The Experience of Thinking: How the Fluency of Mental Processes Influences Cognition and Behavior. Psychology Press, 2013.

“Why Do We Believe Misinformation More Easily when It’s Repeated Many Times?” The Decision Lab, thedecisionlab.com/biases/illusory-truth-effect. Accessed 13 Dec. 2024.