This work presents a systematic analysis of the psychological phenomena associated with the concept of mental representations — also referred to as cognitive or internal representations. A major restatement of a theory the author of this book first developed in his 1971 book (Imagery and Verbal Processes), this book covers phenomena from the earlier period that remain relevant today but emphasizes cognitive problems and paradigms that have since emerged more fully. It proposes that performance in memory and other cognitive tasks is mediated not only by linguistic processes but also by a distinct nonverbal imagery model of thought as well. It discusses the philosophy of science associated with the dual coding approach, emphasizing the advantages of empiricism in the study of cognitive phenomena and shows that the fundamentals of the theory have stood up well to empirical challenges over the years.