Evaluating the Impact of Clutter in Linear Diagrams

Linear diagrams are an effective way of visualizing sets and their relationships. Sets are visualized by a collection of straight line segments and the ways in which the lines overlap indicate subset and disjointness relationships. As with many visualization methods, linear diagrams can become cluttered. In previous research, we established a clutter measure for linear diagrams that was empirically shown to correlate with perceived clutter. The aim of this paper is to determine the impact of linear diagram clutter on user task performance. An empirical study was conducted with three levels of clutter. Surprisingly, we found that diagrams with a medium level of clutter had significantly slower task performance than low and high cluttered diagrams. Moreover, we found no significant performance difference between the low and high clutter. We concluded that clutter affects the interpretation of linear diagrams. A future research goal is to establish methods for controlling the level of clutter in linear diagrams, such as using multiple diagrams instead of a single diagram, when visualizing sets.