The focus of this paper is methodological and theoretical. By means of a re-analysis of a transcript from a research publication, we attempt to show how the researcher, in a similar way as we have observed teachers in classrooms, guides the students towards more or less general mathematical investigations in the context of solving a task. We intend to raise methodological issues related to the original as compared to our interpretation of the data. In addition, we want to exemplify the starting point of the development of a language of description that allows accounting for the emergence and distribution of unequal attainment in mathematics at the micro-level of classroom interaction.