As a part of becoming competent designers, students need to become aware of, accept, and learn to deal with, three cognitive limits. Students often believe (1) that they can imagine forms and geometries accurately in their mind’s eye, (2) that they can keep complex structures in thought, and (3) that they can predict their behaviour and other properties. But people in general are quite bad at all three of these things. Sketching and making models are necessary to overcome these limitations and to prevent unpleasant surprises when conflicts, omissions, and unexpected effects are discovered too late in the process.
People’s geometric envisioning powers are poor. Our visual systems are prone to allowing conflicting shapes, distorted proportions, or downright impossible geometries. Sketching brings out these flaws, ambiguities, and conflicts. Opportunities as well, by the way. Sometimes two parts turn out to be precisely next to each other for instance, when you were expecting them to be relatively far apart, or at different angles.
Second, our working memories are limited. There are only so many parts or components that we can keep in mind simultaneously. As a rule of thumb, we have place for 7 things in our immediate attention. Most designs will have far more. Especially when the relevant elements of the context that designs interact with are taken into consideration. Again, sketching can help us overcome this limit. A sheet of paper can keep much more in our visual field and thus in our attention, even if only peripherally. Also, models, be they virtual or physical, can help tremendously here.
A third limit concerns the operation of these models. Physical thinking requires training and intuitions about stability, strength, friction, deformation, etcetera, are not something people are born with. Everyday experience gives us a rough baseline, but not enough. Here, sketching can only do so much. Of course, a plan drawing of a building can help us imagine walking through it, and drawing products in use can help us to imagine how they would behave. But models and prototypes, because they can be operated in the actual physical world, are key to exploring behaviour and performance.
None of this is rocket science. And I’ve never met a student that wouldn’t agree that all of the above is true in principle. But I also never met a novice or beginner design student that didn’t vastly overestimate their own abilities on all three counts. “I haven’t drawn it yet, but I have it all figured out in my head!”
In fact, I regularly still do this myself, as do experienced and competent designers I know. These seem to be difficult lessons.