Abstract
Three techniques of perceptual grouping were compared in terms of their effect on people's ability to read maps that always remained visible. The techniques differ in the way they create clusters of objects on map-like displays: by using boundary lines to form adjacent “countries” (Common Region), by coloring “city” symbols that belong to the same, contiguous, country in a unique way (Adjacent Color), or by using color to create spatially non-contiguous, overlapping, clusters (Color Only). Subjects were asked to compare the horizontal orientations of two cities at a time, and, in another task, to compare two distances corresponding to three map cities. Results show that orientation statements were verified faster for same-cluster cities than for differentcluster cities, but only in the Common Region condition. Neither distance estimations nor orientation judgments were distorted by any grouping technique, as indicated by an effect on judgment accuracy. The implications of these results for our understanding of map reading ability in relation to techniques for perceptual grouping are discussed.
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