Abstract. The goal of our study is to evaluate the effect on program comprehension of three factors that have not previously been studied in a single experiment. These factors are programmer expertise (expert versus novice), programming task (documentation versus reuse), and the development of understanding over time (phase 1 versus phase 2). This study is carried out in the context of the mental model approach to comprehension based on van Dijk and Kintsch’s model [(1983) Strategies of Discourse Comprehension. New York: Academic]. One key aspect of this model is the distinction between two kinds of representation the reader might construct from a text: (1) the textbase, which refers to what is said in the text and how it is said, and (2) the situation model, which represents the situation referred to by the text. We have evaluated the effect of the three factors mentioned above on the development of both the textbase (or program model) and the situation model in object-oriented program comprehension. We found a four-way interaction of expertise, phase, task and type of model. For the documentation group we found that experts and novices differ in the elaboration of their situation model but not their program model. There was no interaction of expertise with phase and type of model in the documentation group. For the reuse group, there was a three-way interaction between phase, expertise and type of model. For the novice reuse group, the effect of the phase was to increase the construction of the situation model but not the program model.

Hypertexts present methods to read online texts that are different from those available when reading standard linear texts. Hypertexts give readers more flexibility in choosing paths through the text and in finding relevant information. However, research in hypertext has often shown little or no advantages over the equivalent linear text.

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Wisconsin who helped me to realize that cognitive psychology (not computer science) was what I really wanted to do and that CMU's Psychology Department was the right place to do it. In addition, Rich has been a mentor and a close friend. There are many other friends who deserve special thanks for intellectual and personal support dl,Jring this time, most importantly, Christina Allen, Stephen Casner, Jonathan Cohen, Heather McQuaid, and Lael Schooler. Finally, I must thank my parents for their constant love and encouragement.