When drawings are copied repeatedly in sequence by different people, they tend to undergo characteristic processes of change. Parts of an image become separated out, the whole design is flattened, the outline is emphasized, and perspective occlusion is removed. The drawing becomes more abstract, more schematic—in a word, more diagrammatic. This article focuses on such drawing processes and on the results of experiments in repeated copying by anthropologists, psychologists, architectural students, and Surrealists. The tentative conclusion is that designs are represented mentally in a ‘diagrammatic’ way that affects not only how they are seen but also how they are changed when reproduced.