@inbook { prada08, abstract = {Autonomous virtual agents have the potential to promote social engagement of users in virtual environments, thus enhancing their interaction experience. This effect is supported by the interactions users and virtual agents perform together. These interactions are often in group scenarios, where both users and agents perform collaborative tasks. However, in order to have successful group interactions, it is not enough to assure that the characters behave in a coherent manner from an individual perspective, it is also necessary that they exhibit behaviours that are coherent with the group’s composition, context and structure. Furthermore, nurturing social intelligence in virtual agents has been a major concern in the community of multi-agent systems, specially to endow them with skills to perform well in group tasks. However, when building agents to interact in group with users, to perform well in the task does not, necessarily, assure a good interaction experience. While, it is true that users expect the members of their group to perform well in the task, they also expect believable dynamics of the interpersonal relations. In this chapter, we will present a model (SGD Model) to support the dynamics of group interactions that incorporates task related interactions as well as social emotional ones. The model defines the knowledge that each individual should build about the others and the group, and how this knowledge influences its action decision. We will also describe a study that was performed to assess the effect of the SGD Model in the interaction experience of users while playing a collaborative game with virtual counterparts.}, chapter = {New Advances in Virtual Humans: Artificial Intelligence Environment}, edition = {Nadia Magnenat-Thalmann, Lakhmi C. Jain, Nikhil Ichalkaranje}, keywords = {group dynamics, teamwork, social intelligence, autonomous synthetic characters, believability, computer–human interaction}, month = {September}, pages = {113-132}, publisher = {Springer Berlin / Heidelberg}, series = {Studies in Computational Intelligence}, title = {Social Intelligence in Virtual Groups}, volume = {140}, year = {2008}, author = {Rui Prada and Ana Paiva} }