JULIE AMADOR PROFESSIONAL NOTICING PRACTICES OF NOVICE MATHEMATICS TEACHER EDUCATORS Received: 3 September 2013; Accepted: 3 August 2014 ABSTRACT. The focus on professional noticing in mathematics education has recently gained increased interest as researchers work to understand how and what is noticed and how this translates into practice. Much of this work has focused on the professional noticing practices of inservice teachers and preservice teachers, with less attention focused on those educating teachers. This research explores how novice mathematics teacher educators professionally notice as they engage in teaching experiments and create models of student’s mathematical thinking. Findings indicate the novice teacher educators are including some evaluative comments in their professional noticing practices but lack in- depth interpretive analysis about student thinking and rarely make connections between student’s thinking and the broader principles of teaching and learning. These findings provide evidence for the importance of supporting teacher educators with developing their abilities to professionally notice. KEYWORDS: mathematics, model building, professional noticing, teacher educators, teaching experiments As educators engage in teaching, experts are distinguished based on what they professionally notice as well as what they do not notice; those who excel emulate an observer of practice as they engage in professional opportunities (Miller, 2011). As highlighted in the work of Jacobs, Lamb, & Philipp (2010), professional noticing demands that teachers attend to students’ thinking, interpret their thinking, and make decisions about how to respond based on their own assertions. Noticing student thinking is an intentional act requiring active engagement from the educator (Mason, 2011; Sherin, Jacobs, & Philipp, 2011). The assumption is that educators who come to notice student thinking and make decisions based on what is noticed will implement lessons focused on what students know and need to learn. The focus on professional noticing in mathematics education has recently gained increased interest as researchers work to understand how and what is noticed and how this translates into practice (Star & Strickland, 2008; van Es, 2011). Much of this work has focused on the professional noticing practices of inservice teachers, finding that the development of professional noticing is dependent on extended opportunities to focus on students’ thinking and make connections International Journal of Science and Mathematics Education (2016) 14: 217Y241 # Ministry of Science and Technology, Taiwan 2015