Building on the conceptual framework (Chapter 1) and the theoretical foundation (Chapter 2) of comprehensible input (CI), this chapter presents a comprehensive account of the term from the views of five subfields of linguistics. The applied linguistics section focuses on the role of CI in L2A and use in different contexts while the sociolinguistics section discusses how CI relates to sociolinguistic variation (e.g. indices of social categories) and micro- (e.g. discourse) and macro-level (e.g. power) aspects of language use in society. The psycholinguistic section concentrates on the nature of cognitive processes (e.g. recognition), style and speech act, as well as positionality and identity formation in L2A and use. While the neurolinguistics part describes the relationship between language and the brain (neurocognitive and neurobiological) and the structure of language faculties (locations in the brain), the computational linguistics section examines the intersections of neuroscience, cognition and mathematics with the complex nature of input and its comprehensibility.

Applied Linguistic Perspectives

As an interdisciplinary field, applied linguistics (AL) covers a broad range of topics related to why and how languages are learned and used in particular ways by different people or social groups in different contexts (Davies & Elder, 2004; Schmidt, 2002). Thus, by generating theoretical, research-based and pedagogical knowledge, AL contributes to the individual lives of people and the well-being of communities around the world regarding solutions to numerous languageand culture-related problems. AL draws on theory and research in numerous areas of study, including educational psychology, literacy and language acquisition and language policy, pedagogy and assessment, as well as applications of sub-linguistics fields, linguistic theory, society and culture, sign language, translation and interpretation and language and computer technology. The nature, content and methodological orientations in which AL intersects are rather vague and controversial. Without delving into the ontological and epistemological tenets (e.g. AL versus linguistics applied) of the field (Davies & Elder, 2004), it appears that the field has historically allowed for different aspects of these enumerated topics to take centrality in theory and research.