Small Multiples

Small multiples exploit a foundational property of human perception: the capacity to detect minute differences between similar things placed in spatial proximity. Present two nearly identical images side by side and the eye registers discrepancies that would be invisible if the images were shown ten seconds apart. Small multiples codify this capacity into a design form. A grid of maps showing population density by decade. A series of scatter plots showing the same variables across experimental conditions. A sequence of charts in which everything stays constant except the one variable under analysis. The consistent format eliminates confounding variables; the spatial proximity enables direct comparison; the reader's attention is freed to focus on what varies rather than on what stays the same. Tufte has argued that small multiples are often the best design form available when the analytical task is comparison — which, he has also argued, is most analytical tasks.