This paper reports partial results of a broader research entitled: Pedagogical Content Knowledge of Formative Research in three undergraduate programs at the Universidad del Atlántico.The purpose of this study is to develop a profile of pedagogical interaction of teachers from observable behaviors in the classroom that allow infer what pedagogical reasoning processes.The data collection techniques were non-participant observation.The main instrument of data collection is an observation rubric of pedagogical interactions.Results reveal differences between expert teachers and student teachers modes of interaction and thinking.The discussion involves pioneered researches of using categories of pedagogical thought.The findings point to the benefits of investigating expert teachers and student teachers Pedagogical Reasoning.