This book provides an overview of affective individual variables that are considered relevant for second language learning and outlines a novel approach to researching them. In the first part of the book, the most prominent concepts and theories in connection with affective individual variables and tasks are discussed, followed by a literature review of the most significant empirical studies conducted on the reviewed individual variables with the help of tasks. The second part of the monograph reports the findings of a research project which investigated the relationships of motivation, emotions, flow experiences, and self-efficacy beliefs of secondary school students studying English in Hungary. These constructs are examined at two levels: in connection with learners’ English classes in general and in connection with a particular language task, thus linking task performance measures to specific affective states experienced while performing a task and their general trait versions reported in connection with the language classes. Teacher interviews provide further insights into the language tasks used by the teachers of the students taking part in the study and their affective correlates. The book offers multi-level interpretations of the results, puts forward pedagogical implications, and delineates further research directions.