In the new age of information, the ability to discern truth from falsehood has become more relevant than ever. The current project aims to gain insight into human judgment about the truthfulness of information, beyond mere accuracy, focusing on the type of errors that people tend to make. Indeed, when making incorrect judgments about truthfulness, people can judge factually incorrect information as true (= being too gullible), or can judge factually correct information as false (= being too skeptical). The proposed project advances that people show an overall tendency towards gullibility, but are unaware of this tendency, and judge themselves as relatively skeptical. Building on theoretical insights from social and cognitive psychology, and applying methods from psychophysics, in three research lines, we examine gullibility, its flawed self-assessment, and contributing factors. First, we test actual and self-perceived gullibility in a neutral context, investigating the impact of domain-specific knowledge as well as general factors that may underlie flawed self-assessment of gullibility: perceived undesirability of gullibility, and salience (memory) of skeptical answers. Second, we focus on gullibility and its self-assessment in emotionally charged contexts (politics and climate change), examining the role of attitude congeniality and emotional investment. Finally, we study whether, and in which form, feedback can reduce gullibility, and enhance self-perceptions of gullibility