Embedded Falsehoods: How Misinformation Amid Truth Influences Public 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 studying the effects of exclusively false vaccination information. To address this gap, we conducted a large Signal Detection Theory experiment (N = 2,100) to examine how different information environments—those that mix truths with falsehoods versus those presenting exclusive falsehoods—affect vaccination belief accuracy, confidence in these beliefs, and attitudes. Results revealed common and distinct effects across information environments. Common effects included consistent shifts in truth discernment (d’; reducing participants’ ability to differentiate truth from falsehood) and response bias (c; increasing overall gullibility) in response to misinformation. Additionally, vaccination misinformation consistently raised False Positives (accepting falsehoods), with minimal impact on Misses (rejecting truths), and this pattern extended to metacognitive judgments, where misinformation selectively increased confidence in believing falsehoods without diminishing confidence in truths. ... mehrDifferential effects emerged primarily in relation to belief accuracy: While exclusive misinformation most effectively impaired truth discernment (d’), environments mixing truths with logically inconsistent falsehoods (“bullshit” environments) most effectively shifted response bias (c), fostering generalized gullibility. By highlighting the common and distinct effects of exclusive falsehoods and mixed information environments, this study deepens our understanding of a defining feature of pandemic-era information landscapes: the simultaneous exposure to vaccination facts and falsehoods.