The authors of Art and Fear tell us a now-classic parable about a pottery class: The instructor divides the class in half and tells one half that they will be graded solely on quantity, while the other half need only produce one perfect pot in order to get a good grade. By the end of the semester, however, the best-quality works were all produced by the group being graded on quantity. Lots of practice, lots of mistakes, and growing familiarity with the material led them inevitably to the best designs in the end. Rapid, iterative, parallel prototyping provably leads to better design.
Prototyping allows us to solidify and test out our design ideas. Every prototype we create during a design process teaches us something. Making a prototype allows us to see our design roughed out and in action, to better identify opportunities and areas that need improvement. In a project with multiple co-dependent parts (e.g., hardware and software, or electronics and encasing) prototypes of each component can allow us to make better progress on the others.
The increasing availability of excellent prototyping materials makes this process ever more fruitful. Arduino allows us to quickly prototype hardware, while Processing allows us to prototype software interaction in the blink of an eye. Apps like LiveView let us extend that capability to iPhone and iPad prototyping. Materials such as hand-moldable plastic and tools like 3D printers and laser-cutters are ever more readily available and augment traditional techniques involving wood, molding, and workshop tools. With experience using all these techniques, we are well-equipped to create quick and informative prototypes for just about any interaction design project.