Abstract : Design processes rely on the interaction between virtual space of possibility and real space of constructability: this interaction is performed and managed in the designer's mental space. In contemporary Non Standard architecture formal complexity and digital tools are creating a growing gap between virtual space (possibility) and real space (constructability). Our these's aim is to contribute at the understanding of the position of designer's mental space face to this gap. One of our objectives was the definition of a scientific reference frame for the experimental study of the relationships between the designer's mental space and the world's physical space. Cognitive sciences provided the methodology and tools necessary to perform a scientific study of those questions. Two experiments were conduced to identify geometrical invariants and laws which could relate the formal qualities of physical space objects and the correspondent mental space representations. Our results revealed significant data about the perceptual elaboration of the formal qualities of curvature and of complex spatial configurations, in relation with different representation tools (physical scale models, numerical models, drawings).