Responsive teaching is like having a discussion with your students. It’s the practices of attending and responding to the substance of students’ thinking. In order to know the substance of students’ thinking in our advanced physics courses, we use a variety of low-tech formative assessments that help the instructor see student reasoning as it happens, including kinesthetic activities, solving problems in small groups, and small whiteboard questions. Small whiteboard questions, or SWBQs (pronounced “swibik”), paired with a Peer Instruction/Think-Pair-Share strategy, is my go-to pedagogy for both introductory and advanced courses. I will talk about how to use SWBQ’s effectively as a responsive teaching practice.