To identify conditions that make a conversational interaction constructive--in the sense that the participants can find the way toward the success of what they wanted to accomplish--two situations were examined. In one, a professional researcher explained her data to a statistician. In the other, three groups of two people cooperated with each other to figure out how a sewing machine made its stitches. The goal for the statistics problem was to identify conditions for schema changes. It was observed that the two participants had different "starting" schemata, a situation that helped them to come to a constructive conclusion. Starting positions and end results were individualistic; the value of interaction came from the different understanding of the current topic that the participants applied to the interaction. 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 proceeded 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 the errors 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 needed to be changed, it seemed necessary to have a global understanding of the old schema as well as attention to the place where the change was to take place. (HOD)