  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 Ph.D. 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.
