A framework called 'a function-mechanism hierarchy' was developed to capture a course of understanding in the sewing machine interactions. According to this framework, understanding proceeds from global, functional understanding to local, mechanistic understanding by descending 'levels.' The subjects' conceptual point-of-view was related to this course of understanding. Point of view shifted more when the subjects felt they were not understanding, and this shift appeared to help them descend the levels. People corrected more errors when they reflected the current level of understanding; errors were not corrected when they belonged to already known levels. For both statistics and sewing machine interactions, the issue of 'focus' was identified to be important in understanding. When a schema needs to be changed, it seems necessary to have a global understanding of the old schema as well as attention to the place where the change is to take place. Two person interactions have virtues because the participant can take different roles in the interaction and divide the labor: While one person leads the interaction by engaging in the local task, the other can observe and provide help by criticising and bringing up new motions. (Author)