Erik Jacobson is Assistant Professor of Mathematics Education at Indiana University. He received a PhD in mathematics education in 2013 from the University of Georgia. His research focuses on how mathematics teachers develop knowledge and beliefs—including those related to equity and diversity—that support effective instruction. In particular, he studies the affordances of instructional activity (i.e., rehearsal, simulated “micro-teaching,” tutoring, and classrooms instruction) both to assess and to change what teachers know and believe. He was the recipient of an AERA Dissertation Award for a secondary analysis of TEDS-M data that revealed relationships between the type of early field experience in elementary teacher preparation programs and program outcomes including mathematics-related knowledge and beliefs. He currently directs an NSF-funded research project, Assessing the Structure of Knowledge in Teaching Mathematics. This project is developing a multidimensional assessment of pedagogical content knowledge for teaching fractions and decimals to investigate how knowledge, teaching practices, and student learning are reciprocally related at the grain-size of specific curriculum standards. A second ongoing research project, Mathematics Teachers' Beliefs and Practices, is examining how preservice teachers’ perceptions of student gender and race/ethnicity—and their beliefs about who is (or can be) mathematically brilliant—are related to instructional decisions. His work has been published in research journals including the Journal of Research for Mathematics Education and the Journal of Mathematics Teacher Education and in practitioner journals including Teaching Children Mathematics and the Mathematics Teacher.