The timeworn claim that a picture is worth a thousand words is
generally well-supported by empirical evidence, suggesting that diagrams and
other information graphics can enhance human cognitive capacities in a wide
range of contexts and applications. But not every picture is worth the space it
occupies. What qualities make a diagram an effective and efficient conduit of
information to the human mind? In this article we argue that the best diagrams
depict information the same way that our internal mental representations do.
That is, “visual thinking” operates largely on relatively sketchy, cartoon-like
representations of the physical world, translating sensory input into efficient
codes before storing and manipulating it. Effective diagrams will assist this
process by stripping away irrelevant detail while preserving or highlighting
essential information about objects and their spatial relations. We discuss
several examples that illustrate this “Representational Correspondence
Principle,” and we consider its implications for the design of systems that use
diagrams to represent abstract, conceptual knowledge, such as social networks,
financial markets, or web content hierarchies.