She is a cognitive and developmental psychologist who studies children’s knowledge and communication about mathematical concepts. Her research focuses on mechanisms of knowledge change in cognitive development and learning. In particular, she investigates the change processes that take place when children learn new concepts and problem-solving strategies, and when they express and communicate their knowledge in gestures and in speech. Her current research projects examine the function of spontaneous gestures in thinking and speaking, the transition from arithmetic to algebraic reasoning, and the nature of mathematical reasoning and communication in children with language impairments. Her work has been or is currently funded by the U.S. Department of Education, the National Science Foundation, the National Institutes of Health, the James S. McDonnell Foundation, the Spencer Foundation, and the Interagency Educational Research Initiative. She earned her Ph.D. in Psychology at the University of Chicago.