“…In this context, we have seen an emphasis on the need for teachers to base their teaching decisions on their students' learning characteristics of mathematical content (Franke & Kazemi, 2001). This has raised a number of questions about the way in which teachers notice the signs of students' understanding (An & Wu, 2012;Fernandez, Llinares & Valls, 2012;Magiera, van den Kieboom & Moyer, 2013) and about the development of this skill (Bartell, Webel, Bowen & Dyson, 2013;Fernández, Llinares & Valls, 2013;Wilson, Mojica & Confrey, 2013;Spitzer, Phelps, Beyers, Johnson & Sieminski, 2011). These research studies support the idea that teachers must know how students understand mathematical topics in order to make appropriate teaching decisions.…”