Dunn, Richard, Framed Rectangle Charts or Statistical Maps with Shading: An Experiment in Graphical Perception, American statistician , 42(2), 1988, pp. 123-129
This article presents and discusses the results of an experiment in human graphical perception designed to assess the relative accuracy with which quantitative information is extracted from a framed rectangle chart compared to an unclassed choropleth map.The basis for and results of this experiment are discussed in relation to recent developments in theories of graphical perception and statistical mapping.