Computational models of expressive behaviors for a virtual agent

Expressive behaviors are an indispensable part of any believeable virtual agent. They add liveliness to the virtual character and allow for clearer communication. This chapter is dedicated to computational models of expressive behaviors. The variety of these models arise from the richness of the theories trying to explain human behavior. For this reason, first the chapter introduces the main theories of human expressive behavior and then classifies computational models according to them. Expressive behaviors based on interactions not only consist of the choice of the appropriate set of nonverbal signals (e.g., facial expressions, gestures) to express agent's intentions but also in their appropriate realization. For this reason, the authors also present the computational models of expressive and dynamic qualities of a movement. Finally, the expressive behavior can be influenced by social context or the behavior of its interlocutor. The authors conclude this section by presenting models of regulation of emotional expressions