Susan B. Empson is an Associate Professor of Science and Mathematics Education at The University of Texas at Austin. Her research has been supported by the National Science Foundation and the Spencer Foundation, and has been published in numerous journals including Cognition and Construction, Journal for Research in Mathematics Education, Teaching Children Mathematics, and Journal of Mathematics Teacher Education. Susan was coauthor of Heinemann's top selling math title Children's Mathematics: Cognitively Guided Instruction, which has helped tens of thousands of teachers understand children's