As transfer researchers have begun to investigate a broader range of phenomena, they have correspondingly put forward new processes to provide explanatory accounts for the occurrence of transfer. This move coincides with a call to acknowledge the contribution of social interactions, language, cultural artifacts, and normed practices to the generalization of learning. In this article, we posit "noticing" as a plausible transfer process and investigate both individual noticing and the social organization of noticing via the "focusing framework". Specifically, we relate the nature of students' reasoning on transfer tasks with what students notice mathematically in classrooms when many sources of information compete for their attention, and then we account for noticing as socially situated in classroom discourse practices, features of mathematical tasks, and the nature of mathematical activity. (Contains 16 figures and 4 tables.)