His research examines what happens when learners form beginning conceptions of complex concepts at the middle and high school levels. More specifically, he is interested in the phenomenon of backward transfer, which is how learning something new influences a learner’s prior knowledge. For example, he has conducted a study that investigated how middle school students’ prior knowledge of linear functions changed as a result of learning about quadratic functions. Recently, he discussed his recent article on teachers’ awareness of the relationship between prior knowledge and new learning on Math Ed Podcast.