Values. Uses. Materials: the expression of users in the co-creation through virtual and tangible representation systems.

Co-creation [1] aims to involve users at the heart of the design process. The specificity of this approach is to allow for a more detailed identification of the activities and future needs of users through a practice of « making ». But to genuinely participate in design ideation, end-users must be provided with proper representation tools. Therefore, these assumptions lead to two main questions: what kind of ideas do users actually produce in co-creation workshops? And how VR and tangible representation support the expression of those ideas? In this study, we analyze the development of the core concept of a 7-participants groups involved in the design of a University Lobby, supported by a hybrid tangible/virtual representation system. We explore, through the prism of levels of abstraction [Rasmussen 1983], how the core concept is gradually shaped and the roles of tangible and virtual representations, as well as the real space to be designed, in the co-creation process. We show that participants succeed in designing very concrete features but that core decisions are taken on an abstract level. Representations support expression of concrete ideas, but we found no difference between virtual and tangible tools. We conclude on perspectives to deepen this ongoing work.