Repetition and modality in information trustworthiness judgments: Investigating the illusory truth effect in multimodal health information environments

The illusory truth effect, in which repeated exposure increases trust regardless of accuracy, poses significant challenges to the perceived trustworthiness of health information in digital environments. Although repetition is known to enhance cognitive fluency, little is known about how different modalities influence this effect. Drawing on cognitive fluency and dual‐coding theories, this research investigates how repetition and modality interact to shape trustworthiness judgments of health information. Three online experiments were conducted to examine users' perceived trustworthiness of health information across different conditions. Experiment 1 the effect of repetition on messages varying in truthfulness (true vs. false) and familiarity (familiar vs. unfamiliar). Experiments 2 and 3 examined the role of modality (text‐only, text‐and‐image, short video) and cross‐modal repetition. Results show that, in the text‐only condition, an unfamiliar true message is perceived as more trustworthy than other information. Repetition significantly increases perceived trustworthiness in text‐and‐image and short video formats, albeit with diminishing returns after two exposures. Cross‐modal repetition further amplifies such trustworthiness effects. These findings extend theoretical understanding of the illusory truth effect in multimodal health information environments and offer practical insights for designing interventions to reduce the spread of misinformation on social media.