The study reported in this paper applies the commognitive theory as a lens to study teacher learning in lesson study to better understand how and why teachers learn from lesson study. Video recordings were made from reflection meetings in three lesson study cycles with a group of four Norwegian lower secondary school teachers, one person from the school administration and a participating observer. The research revealed the potential of commognitive conflicts to explain teachers' pedagogical discourse. The analyses identified and described patterns in the teachers' pedagogical discourse when focused on observations of student learning during the reflection meetings. The discourse aligned more with a pedagogical delivery discourse rather than an explorative pedagogical discourse that was the aim of lesson study participation. Three examples illuminate the mismatch in the teachers' discourse with the canonical pedagogical discourse.