Finding ways to better understand prospective teachers' development is central to teacher preparation. To effectively foster development, teacher educators must determine how their students conceptualize and understand teachers' work: How do they understand learning and learners? What are their general and specific understandings of subject matter? How do they understand the lines of action open to teachers and the consequences of the various choice made? How does their understanding of each of these aspects of teaching help them build a coherent and integrated understanding of teaching? The "new science of learning" tells us that to foster student understanding one thing teachers must do is to work with the understandings students bring with them and provide opportunities for students to take more control of their own learning (Bransford, Brown, & Cocking, 1999). To do this, teachers must first determine what those understandings are.