During the last few days we have seen several examples on how it has become possible to use refined methods to study how man perceives and reacts to the built environment. There have been many examples on the advancement of technique and knowledge within this field. We have also been complaining over the lack of communication between architects and psychologists, i.e. the discrepancy between knowledge about man's reactions on his environment on one side, and knowledge about those physical and social realities, which form the environment on the other side. The psychologist has his rather elaborate field and the architect has his. What remains is to develope that field which we ought to share, i.e. to chart the relations between what we perceive and how it is perceived. There is a need of useful models to relate stimuli to perceptions. Such models are a necessary prerequisite for the much demanded cooperation between consumer, psychologist and architect in the process of planning.