Does expertise within a domain of knowledge predict accurate self-assessment of the ability to explain topics in that domain? We find that expertise increases confidence in the ability to explain a wide variety of phenomena. However, this confidence is unwarranted; after actually offering full explanations, people are surprised by the limitations in their understanding. For passive expertise, miscalibration is moderated by education; those with more education are accurate in their self-assessments. But when those with more education consider topics related to (...) their area of concentrated study, they also display an illusion of understanding. This “curse of expertise” is explained by a failure to recognize the amount of detailed information that had been forgotten. While expertise can sometimes lead to accurate self-knowledge, it can also create illusions of competence. (shrink)