How do modelers read UML diagrams?: preliminary results from an eye-tracking study

Background: Conceptual diagrams are widely used. Previous research suggested layout quality, diagram size, and expertise level are relevant impact factors on understanding, while diagram type is not. Surprisingly little is known about how diagrams are read. Objective: Eventually, we want to understand the cognitive processes of diagram and model understanding. In this paper, we study the behavior of modelers while reading UML diagrams in terms of reading strategies and how they affect diagram understanding. Method: We conduct an eye tracking study with 28 participants, reusing diagrams and items from previous experiments. We record several objective and subjective performance indicators as well as eye movement and pupil dilation. Results: We discover behavioral regularities and aggregate them into reading strategies which vary with expertise level and diagram type, but not with layout quality. Conclusions: Modelers exhibit specific strategies of diagram understanding. Experts employ different strategies than novices, which explains performance differences irrespective of layout quality.