Introduction to teacher cognition -- Foundations for the study of teacher cognition: a cognitive modeling perspective -- A cognitive model of pedagogical reasoning -- A study of collaborative pedagogical reasoning -- A study of individual pedagogical reasoning -- Outcomes of the two studies -- The added value of collaboration in learning and performance: cognitive and social cognitive modeling as a rationale and strategy for empirical investigations -- An essay on the nature and structure of teacher knowledge -- Epilogue: from a research agenda to contributions to teacher education on a trajectory to expertise in pedagogical reasoning.