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A long tradition of scholarship, from ancient Greece to Marxism or some contemporary social psychology, portrays humans as strongly gullible—wont to accept harmful messages by being unduly deferent. However, if humans are reasonably well adapted, they should not be strongly gullible: they should be vigilant toward communicated information. Evidence from experimental psychology reveals that humans are equipped with well-functioning mechanisms of epistemic vigilance. They check the plausibility of messages against their background beliefs, calibrate their trust as a function of the source’s competence and benevolence, and critically evaluate arguments offered to them. Even if humans are equipped with well-functioning mechanisms of epistemic vigilance, an adaptive lag might render them gullible in the face of new challenges, from clever marketing to omnipresent propaganda. I review evidence from different cultural domains often taken as proof of strong gullibility: religion, demagoguery, propaganda, political campaigns, advertising, erroneous medical beliefs, and rumors. Converging evidence reveals that communication is much less influential than often believed—that religious proselytizing, propaganda, advertising, and so forth are generally not very effective at changing people’s minds. Beliefs that lead to costly behavior are even less likely to be accepted. Finally, it is also argued that most cases of acceptance of misguided communicated information do not stem from undue deference, but from a fit between the communicated information and the audience’s preexisting beliefs.