Chapter 1 introduces linguistic illusions, focusing on how the mind processes language in real time and how systematic errors, such as agreement attraction, occur. The chapter first explains how linguistic illusions are cases where listeners or readers misunderstand or fail to notice anomalies in language. Agreement attraction, a phenomenon where mismatched subject–verb agreement is overlooked due to interference from nearby elements, serves as the primary case study. The chapter draws parallels between linguistic illusions and optical illusions, emphasizing that while both reveal discrepancies between perception and reality, linguistic illusions are more probabilistic and context dependent. This chapter also sets up the importance of studying these illusions to uncover fundamental cognitive mechanisms and processes underlying language comprehension. By systematically analyzing linguistic illusions, researchers can gain deeper insights into the cognitive architecture of language and the role of memory encoding and retrieval in language processing. The chapter concludes by outlining the book’s structure and key questions that the study of linguistic illusions aims to answer.