Teaching experiments as a methodological approach to Mathematics Education Research

Teaching experiment is a useful methodological approach in mathematics education research to study how students learn. The objective of this article is to present the characteristics of this methodological approach, through the development of a teaching experiment in a third grade of primary education with 9-year-old students. This teaching experiment is aimed at supporting the learning about the concept of polygon. We exemplify the characteristics of this approach in mathematics education research by underlining (i) use of theories about learning in the design of activities, and (ii) diverse information sources that provide a triangulation of inferences that can emerge. Finally, possible uses of the practice records derived from teaching experiments for teacher training are noted.