This collaborative concept-mapping exercise was conducted in a second-year mathematics methods course. Teachers' visual representations of their mathematical content and pedagogical knowledge provided insight into their understanding of how students learn mathematics. We collected 28 preservice student teachers' concept maps and analyzed them by counting the number of concepts and links within and across knowledge, teaching, and learning. We also examined the nature of the links between two domains of concepts. Preservice teachers revealed limited knowledge about how students learn mathematics. Concept maps successfully identified areas in which preservice teachers held an unsophisticated understanding of mathematics and its connection to pedagogy.