The Visual Rhetoric of Data Displays: The Conundrum of Clarity*

The visual rhetoric of data displays (e.g., charts, graphs, maps) has changed profoundly over the past 50 years as a result of research in display techniques, the application of traditional and emerging rhetorical approaches, and the democratizing effects of data design technology. Perhaps in no other visual realm than data design is the notion of clarity more critical or more contested. Indeed the ascendancy of rhetorical approaches was initiated by the perceptual/cognitive science of data design, which in seeking to identify optimal display techniques, fostered a concern for ethics and evoked the universality and minimalism of modernist aesthetics. The rhetoric of adaptation, which emphasizes the variability of audiences, purposes, and situational contexts, rendered clarity contingent and mutable-a moving target that requires constant attention. Social rhetoric considered data design as a collective construct, tethering clarity to visual discourse communities, convention-building, cultural values, and power. The concept of clarity has been further reoriented by the rhetoric of participation, which is fostered by interactive digital design that enables users to adapt displays according to their needs and interests.