Novice Rationales for Sketching and Tracing, and How They Try to Avoid It.

Prior research has shown that sketching out a code trace on paper is correlated with higher scores on code reading problems. Why do students sometimes choose not to draw out a code trace, or if they do, choose a different sketching technique than their instructor has demonstrated? In this study, we interviewed 13 CS1 students retrospectively about their decisions to sketch and draw on a recent programming exam. When students do sketch, we find that their sketching choices do not always align with a strict execution of the notional machine. Sketching choices are driven by a search for a program's patterns, an attempt to create organizational structure among intermediate values, and the tracking of prior steps and results. When novices don't sketch, they often report that they've identified the goal that the code achieves. In either case, novices are searching for the functionality of code, rather than merely tracing its behavior.