Pandemic Preparedness and Embedded Falsehoods: How Misinformation Amid Truth Influences Perception of Vaccines

Pandemic preparedness requires understanding how vaccination misinformation functions in typical pandemic-era information environments which expose citizens to both true and false vaccination information. However, prior experiments predominantly focused on the effects of exclusively false information, rather than more structurally complex information environments. To address this gap, we conducted a highly powered Signal Detection Theory experiment (N = 2,805) examining how different information environments—exclusive falsehoods, exclusive truths, and mixed true–false environments—shape vaccination belief accuracy, confidence, and attitudes. Relative to a true-only baseline, we identified both shared and distinct effects across misinformation environments. Common effects revealed that all misinformation environments undermined truth sensitivity, confidence in True Positives (believing true statements), and vaccination attitudes, while not affecting confidence in False Positives (believing false statements). Differential effects revealed that exclusively false environments most effectively reduced truth sensitivity and shifted vaccination attitudes, while mixed environments were more effective at shifting response bias.