My research explores the conceptual development of students in student-centered learning environments. I am interested in the evolution of the system as a whole, including students, tools, teachers, course materials, and the interactions among these components. Another current research interest stems from experience working with prospective and practicing K-12 teachers. Reform methods often encourage the elicitation of students' prior knowledge, but several different notions of what to do with that prior knowledge exist within the community of educational practitioners and researchers. I am currently working to understand how prospective and practicing teachers conceive of students' prior knowledge and how they capitalize on it to empower students to inform their own teaching and as a resource on which students can build.