What architects see in their sketches

Freehand sketches are essential for crystallizing ideas in the early stages of design. Through the act of putting ideas down on paper and inspecting them, designers see new relations and features that suggest ways to refine and revise their ideas. We claim that seeing different types of information in sketches is the driving force in revising design ideas. Our retrospective protocol analysis revealed that sketches make apparent to designers not only perceptual features but also inherently non-visual functional relations, allowing them to extract function from perception in sketches. This has implications for ways that future sketching tools can stimulate designers to come up with creative ideas.