Susan Empson studies the teaching and learning of mathematics in elementary and middle-school classrooms. Her current work focuses on the role of professional development in teacher learning and the development of responsive decision making in the domain of rational numbers. Her research has been supported by the National Science Foundation and the Spencer Foundation, and published in such journals as Cognition and Instruction, Journal for Research in Mathematics Education, Teaching Children Mathematics, and Journal of Mathematics Teacher Education. She earned her PhD in Mathematics Education at the University of Wisconsin-Madison and has worked on the Cognitively Guided Instruction project. Before going back to graduate school, she was a high school mathematics teacher in New York City at A. Philip Randolph High School, and in the Peace Corps, in Morocco.