International Group for the Psychology of Mathematics Education (PME)

Proceedings of the International Group for the Psychology of Mathematics Education · Volume 1

Discovering “whys” Behind the Change Side–change Sign Rule in Algebra

Anna Baccaglini-Frank, Bernardo Nannini, Federica Poli

University of Pisa

49th Annual Conference of the International Group for the Psychology of Mathematics Education, PME 2026Helsinki27 July 2026 - 1 August 2026pp. 115–122ISSN 2790-36482026Scopus conference code 336559
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Abstract

The change side–change sign procedure (CS procedure) for equation solving is often used by students as a memorized rule without justification. This paper reports on findings from the DynaMat project that sees remediation not as repetition of procedures, but as access to mathematical meaning through Digital Exploratory Objects (DEOs). Grounded in Commognition, the study analyzes a case of two grade-10 students to investigate whether and how the remedial activities supported the substantiation of the CS procedure. The findings show that the intervention supported students through a guided process of discourse expansion with the DEOs, followed by a compression in which the CS procedure came to be seen as a substantiated shortcut.

Keywords

commognitionchange side-change sign rulecompressionrote memorizationsense-making

Recommended citation

Baccaglini-Frank, A., Nannini, B., & Poli, F. (2026). Discovering “whys” Behind the Change Side–change Sign Rule in Algebra. In Krzywacki H., Hähkiöniemi M., Haataja E., Hannula M.S., Hästö P. (Eds.), Proceedings of the International Group for the Psychology of Mathematics Education, Volume 1 (pp. 115–122). Psychology of Mathematics Education (PME). ISSN 2790-3648.
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