Pedagogical Knowledge Among Early-Career Undergraduate Instructors: Qualitative Variation, Longitudinal Development, and Influences on Teaching.

Active learning can enhance student outcomes in STEM higher education, but its effectiveness varies with implementation. A key contributor to this variation is the pedagogical knowledge held by instructors. However, little is known about instructors' pedagogical knowledge of how people learn, how these ideas develop over time, and how knowledge development influences active-learning implementation. This longitudinal qualitative study examined variation, development, and instructional implications of pedagogical knowledge among 11 early-career undergraduate life sciences instructors in the context of their active-learning instruction. We conducted semistructured interviews, including stimulated recall, capturing pedagogical knowledge used to plan, implement, and reflect on a lesson, repeating this process across multiple semesters. We used qualitative content analysis and an analytical framework to identify distinct pedagogical ideas about how people learn used by instructors and their alignment with passive, active, and generative cognitive engagement in the ICAP framework. Longitudinal comparisons revealed that participants did not consistently develop ideas aligned with generative cognitive engagement, indicating that teaching experience is necessary but insufficient to foster development of crucial pedagogical knowledge for effective active learning. Case studies illustrated how knowledge development can influence nuances of active-learning design and implementation. We discuss potential mechanisms of knowledge development and instructional implications.