According to the Historical and Cultural Approach and Leontiev's Activity Theory, the subjects' appropriation of concepts and psychic development are interlinked processes. Monitored learning activities on the concept of volume have been developed in a 3rd year primary school class to investigate the students' conceptual process. Children's activities revealed their psychic development as they used geometrical concepts such as monitoring instruments for the solution of challenging situations. Appropriation is revealed when there is a change in the relationship between subject and object, or rather, when the subject quits activities by trial and error or the mechanical repetition of procedures and acts according to reflection and analysis. The latter requires the mobilization of higher psychic functions.
Activity Theory; Scientific concepts; Volume; Learning; Teaching activities