The robustness of repetition-based illusory truth and certainty effects in social media contexts.

In the past, cognitive illusions, such as the repetition-based illusory truth and certainty effects, were primarily studied in experimental settings that were far removed from real-world conditions. However, information channels - particularly social media - provide competing cues (e.g., likes) that may influence such cognitive phenomena. In the present study (N = 165), participants were assigned to one of two groups that viewed Instagram-like posts either with visible like counts (experimental condition) or without them (control condition). In addition, within the experimental group (N = 82), the number of likes was systematically manipulated. Results showed no moderating effect of like visibility on the repetition-based illusory truth or certainty effects. However, especially when repetition-based cues were absent, low (compared to high) like counts substantially reduced both subjective truth and confidence (experimental condition), highlighting the dominant role of information repetition in shaping perceived truth and confidence in truth evaluations.