Most studies of mathematics teacher noticing employ information-processing-based models of noticing. While information processing has been used productively to research the cognitive requirements of noticing, critics have argued that these accounts conceptualise noticing as a relatively passive and mental act. This paper demonstrates how an alternative perception/action cycle model of noticing can draw attention to how teacher noticing is supported by active interaction with the classroom environment mid-lesson. Data from two primary mathematics lessons were gathered using a head-mounted camera technique. These data are analysed using the perception/action cycle model to demonstrate the model's capacity to enable productive research. The model draws attention to aspects of teacher behaviour that support noticing that are given little weight when information processing informs analysis. By contrasting the noticing of one experienced and one beginning teacher, differences in the way that each teacher deployed their attention and looked for information mid-lesson can be ascertained. The experienced teacher took action that increased the likelihood that students would create mathematical representations that enabled perception of students' mathematical thinking and deployed their attention so that they were more likely to be in the right place at the right time to notice. The perception/action cycle model draws attention to these under-researched aspects of mathematics teacher noticing.