This book breaks new ground towards an understanding of the mental processes involved in presupposition, the comprehension of information taken for granted. Various psycholinguistic experiments are discussed to support the idea that involved in ordinary language comprehension are complex and demanding cognitive processes. The author demonstrates that these processes exist not only at the explicit level of an utterance but also at a deeper level of computing, where the background information taken for granted as already known and shared between interlocutors is processed. The author shows that experimental research can suggest new theoretical models for presupposition, thus this book will be of interest to researchers and students of psycholinguistics, the philosophy of language and experimental pragmatics.