In this book literary interior monologue is considered in relation to extraliterary phenomena, as well as narrative theory. The central question posed by this study is: what makes a particular interior monologue believable, given the unobservable nature of human thought? The discussion revolves around the unobservable counterpart of literary interior monologue, i.e., what is known in psychology as inner speech. Taking various experimental findings and theories from Soviet and American research on inner speech, the author compares them with literary interior monologue and tries to account for similarities and differences. Examples of literary interior monologue are analyzed in comparison with data from the linguistic study of real oral spontaneous discourse (also known as face-to-face communication). In the context of this interdisciplinary framework four examples of literary interior monologue are considered: V.M. Garshin's Four Days (1877), E. Dujardin's Les Lauriers sont coupés (1887), A Schnitzler's Leutnant Gustl (1900) and V. Larbaud's Amants, heureux amants... (1921). The inclusion of data from psychology and research on face-to-face communication makes a unique contribution not only to narrative theory, but also to the understanding of the relationship between literary and extraliterary communication.