This chapter presents a state-of-the-art review of existing emotion theory,
modeling approaches, and affective information extraction and processing methods.
The basic theory of emotions deals with Darwin's evolutionary theory, Schechter's
theory of emotion, and James–Lange's theory. These theories are fundamental building
blocks of Affective Computing research. Emotion modeling approaches can be
categorized into categorical, appraisal, and dimensional models. Noticeable
contributions to Affect recognition systems in terms of modality, database, and
dimensionality are also discussed in this chapter.