New research published in Cognition reveals that repeated exposure not only makes people more likely to believe information is true but also falsely remember knowing it beforehand.
The “truth effect’ demonstrates how repeated exposure to a statement can significantly influence our belief in its truthfulness, regardless of its actual accuracy. The ease with which our brain processes these repeated statements—a concept known as processing fluency—is often mistakenly interpreted as a signal of truth.
This effect takes on greater significance with the proliferation of fake news through social media, where sensational and emotionally charged content is repeatedly shared, regardless of its truthfulness. Online platforms exploit the truth effect, embedding misinformation deeper into public consciousness. Memory and knowledge illusions, including source amnesia, further complicate matters by leading individuals to believe they remember or know false information from credible sources.
Researchers Felix Speckmann and Christian Unkelbach recruited 194 participants who evaluated 50 trivia statements in Experiment 1. During the presentation phase, each participant was shown 25 of the 50 statements in a random order. This phase was followed by the judgment phase, where participants reviewed both the previously seen statements and an additional 25 new statements. They were asked to indicate whether they knew the information in each statement prior to the study. The statements covered various topics and were sorted by difficulty (e.g., “A koala’s pouch opens rearward”).
Participants were significantly more likely to report knowing the repeated statements beforehand compared to the new statements. This effect was consistent across different difficulty levels, indicating that repetition substantially influences the perceived familiarity of true statements.
Experiment 2 mirrored the design of Study 1 but with all statements being factually false (e.g., “Golf was originally called mintonette”). It included 191 participants who assessed their prior knowledge of 50 false trivia statements, again divided into 25 repeated and 25 new. The study examined the illusion of knowledge by asking if participants knew the statements to be false.
There was a small but significant increase in the belief that they knew the repeated false statements to be false beforehand compared to the new statements. This suggests that repetition can also enhance the conviction in recognizing false information as familiar.
Experiment 3 recruited 197 participants, following the same basic procedure as Study 1 but added a phase where participants were asked to specify the source of their knowledge after indicating they knew a statement (i.e., “I read it in a book; I read it in a newspaper/ magazine; I heard it on the radio; I saw it on television; I read it / saw it on the internet; I heard it from someone; Other; I do not remember how I know this; I did not know that after all”). This was intended to explore whether providing a source might lead participants to reconsider their initial “known” judgment.
The repetition effect persisted, with participants more frequently reporting prior knowledge of repeated statements. However, very few participants changed their minds about knowing a statement when asked to cite a source, indicating a strong illusion of knowledge effect reinforced by plausible but incorrect source attribution.
Experiment 4 replicated the design of Study 3 but with 191 participants evaluating the false statements from Experiment 2, aiming to eliminate any influence from actual knowledge. After participants judged a statement as known, they were asked where they had heard or seen this information before. Similar to the other studies, repeated statements were more likely to be reported as known.
The study also noted that corrections where participants acknowledged not knowing a statement after all were rare, further highlighting the strength of the illusion of knowledge effect even when the statements were factually incorrect.
Notably, the controlled environment of the study might not fully capture the complexities of memory and knowledge formation in everyday life.
The research, “Illusions of knowledge due to mere repetition”, was authored by Felix Speckmann and Christian Unkelbach.