JOURNAL OF RESEARCH IN SCIENCE TEACHING VOL. 49, NO. 10, PP. 1211–1239 (2012) Research Article Pedagogical Content Knowledge as Reflected in Teacher–Student Interactions: Analysis of Two Video Cases Alicia C. Alonzo, 1 Mareike Kobarg, 2 and Tina Seidel 3 1 Department of Teacher Education, Michigan State University, Erickson Hall, 620 Farm Lane, Room 307, East Lansing, Michigan 48824 2 IPN—Leibniz Institute for Science and Mathematics Education, Kiel, Germany 3 TUM School of Education, Technische Universita ¨t Mu ¨nchen, Mu ¨nchen, Germany Received 4 August 2011; Accepted 14 September 2012 Abstract: Despite the theorized centrality of pedagogical content knowledge (PCK) for teaching, we have little evidence of the relationship between PCK and students’ learning and know relatively little about how to help teachers to develop PCK. This study is a preliminary attempt to address these gaps in our knowledge of PCK through exploration of two German physics teachers’ classroom instruction in consecutive lessons on optics. We show how video analysis can be used to gather evidence for one aspect of teachers’ PCK: their use of content knowledge in interactions with students. We identify three potentially important characteristics of this aspect of PCK: flexibility, richness, and learner-centeredness. By contrasting teachers with high and low gains in student knowledge and interest, we explore potential mechanisms by which this aspect of PCK might affect student outcomes. Because German teacher preparation programs emphasize content more than pedagogical knowledge, these cases contribute to our understanding of the support that teachers with strong content knowledge may need in translating this knowledge into a form useful for teaching. ß 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 1211–1239, 2012 Abstrakt: Fachdidaktisches Wissen ist aus theoretischer Sicht besonders zentral fu ¨r das Unterrichten. Aus empirischer Sicht gibt es bislang allerdings noch wenig Evidenz fu ¨r den Einsatz fachdidaktischen Wissens wa ¨hrend des Unterrichtens und seine Bedeutung fu ¨r das Lernen von Schu ¨lerinnen und Schu ¨lern. Außerdem wissen wir wenig daru ¨ber, wie Lehrpersonen u ¨ber die Zeit fach- didaktisches Wissen entwickeln. Diese Studie ist ein Versuch, diese Wissenslu ¨cken zum fachdidakti- schen Wissen von Lehrpersonen zu bearbeiten. Dabei wird exemplarisch der Unterricht von zwei deutschen Physiklehrern in aufeinanderfolgenden Stunden zum Thema Optik untersucht. Die Studie zeigt wie Videoanalysen genutzt werden ko ¨nnen, um Belege fu ¨r einen Aspekt des fachdidaktischen Wissens der Lehrpersonen zu sammeln: Ihre Nutzung von inhaltlichem Wissen in der Interaktion mit den Schu ¨lerinnen und Schu ¨lern. In dieser Studie werden drei potentiell wichtige Charakteristika dieses Aspekts des fachdidaktischen Wissens identifiziert: Flexibilita ¨t, Reichhaltigkeit und Schu ¨lerorientierung. Durch die Gegenu ¨berstellung von Lehrpersonen mit hohem und niedrigem Wissens- und Additional Supporting Information may be found in the online version of this article. An earlier version of this article was presented at the 2008 annual meeting of the National Association for Research in Science Teaching, Baltimore, MD. Contract grant sponsor: German Research Foundation (PR 473/2-2); Contract grant sponsor: University of Iowa. Correspondence to: A.C. Alonzo; E-mail: alonzo@msu.edu DOI 10.1002/tea.21055 Published online 22 October 2012 in Wiley Online Library (wileyonlinelibrary.com). ß 2012 Wiley Periodicals, Inc.