1 Introduction
Humans are highly social and possess exceptional skills for communication with other humans. A natural approach for immersive virtual reality systems is thus to rely on interactions that are as close as possible to how humans interact with each other. Animated characters and avatars often emerge as key elements for replicating human forms of communication, improving usability and accessibility to all types of users. The approach is promising for several applications in education, training and rehabilitation [1], [2].