David Kirsh has made close observations of the way architects use physical mock-ups of the buildings they are designing; when they interact with the models they have constructed, he maintains, “they are literally thinking with these objects.” Interactions carried out in three dimensions, he says, “enable forms of thought that would be hard if not impossible to reach otherwise.” Kirsh calls this the “cognitive extra” that comes from moving concrete objects through physical space—a mental dividend that made the difference for one scientist struggling with a seemingly insoluble problem.
