This example also relates to the fourth major factor identified by Perry andLewis (2009) as contributing to the shift in participants’ view of Lesson Study –an increased focus on mathematical thinking, with a corresponding change in emphasis from superficial aspects to collecting detailed data on which to base substantive conversations about pedagogy and content. One teacher wasreported as saying:A couple of the Japanese men had documented minute by minute what[students] were doing ... It made me realize as an observer how you can just get warm feelings about some things, but it’s really important to be detailed in your observation and really be critically thinking