How to improve group performances on colocated synchronous manipulation tasks?

Collaborative Virtual Environments provide new working methods to associate several users on the same problem through different space and time configurations (synchronous/ asynchronous, distant/colocated). This new approach enables the simultaneous management of complex environments with several constraints for a more robust and efficient process. Previous studies investigate various features of synchronous Collaborative Virtual Environment but they mainly focus on configurations involving mainly 2 users. This paper presents an experimental study which investigates the collaborative work for more users. We propose to compare 2 users with 4 users to perform a closely coupled molecular deformation task. The results show that groups of 4 participants are more efficient than pairs, even more if they plan their actions during a brainstorming step. An important outcome of this study shows that the role of a leader improve the coordination between the participants and limit the conflicting communication.