Primary teacher preparation courses to need support students in developing not only science content knowledge, but also pedagogical knowledge appropriate to the effective translation and representation of subject matter for learners in classrooms. In the case of the generalist primary trainee, this constitutes a considerable challenge. This study explored how a group of 13 primary trainees developed subject and pedagogical knowledge during university-based training as they investigated shadow production in a variety of contexts using cognitive conflict as a strategy for promoting conceptual change. By using a metacognitive approach, students analysed their own learning in response to increasing depth of conflict within a series of shadow investigations. The results indicate that the depth of conflict perceived by the learners in this study was instrumental in inducing conceptual change and generating pedagogical insight within the domain of light. (Contains 11 figures.)