The ability to categorize problems based upon underlying principles, rather than contexts, is
considered a hallmark of expertise in physics problem solving. With inspiration from a classic study
by Chi, Feltovich, and Glaser, we compared the categorization of 25 introductory mechanics problems
based upon similarity of solution by students in large calculus-based introductory courses with
physics faculty and PhD students. Here, we summarize the study and suggest that a categorization
task, especially when conducted with students working with peers in small groups, can be an
effective pedagogical tool to help students in introductory physics courses learn to discern the
underlying similarity between problems with diverse contexts but the same underlying physics
principles.