Abstract

Presuppositions bypass epistemic vigilance, but it is unclear if this stems from their encoding or their not‐at‐issue status. In a truth‐value judgment task, participants evaluated false statements from a suspect (low reliability) or a witness (high reliability), varying in linguistic encoding (presupposition vs. assertion) and at‐issueness (at‐issue vs. not‐at‐issue). False information was detected faster and more accurately when at‐issue. False assertions were identified faster, while false presuppositions led to more errors when not‐at‐issue. The difference in response time between assertions and presuppositions was smaller for the unreliable source, suggesting that linguistic encoding and source reliability jointly influence false information detection.