  We discuss the categorization of 20 quantum mechanics problems by 6 physics
professors and 22 undergraduate students from two honors-level quantum
mechanics courses. Professors and students were asked to categorize the
problems based upon similarity of solution. We also had individual discussions
with professors who categorized the problems. Faculty members' categorizations
were overall rated better than those of students by three faculty members who
evaluated all of the categorizations. But the categories created by faculty
members were more diverse compared to the uniformity of the categories they
created when asked to categorize introductory mechanics problems.
