How can students’ engagement with instructional videos on generalizing with algebraic expressions be scaffolded?: Design research for specifying the content-specific focus of scaffolds

Generalizing with algebraic expressions and variables is a challenging area of algebra content that requires conceptual understanding. Instructional videos can contribute to conceptual understanding only if students deeply engage with the video content. This deep engagement can be scaffolded by activating design features (e.g., brief prompts). However, limited research attention has been given to specifying their content-specific focus. This paper reports on a design research approach concerning generalizing with expressions, conducted in two design-experiment cycles with 16 students. Through qualitative comparative scaffolding analysis, we specified which content-specific processes needed focus at what moment through which activating feature. The first design experiment cycle, using an unscaffolded video, revealed which processes occurred spontaneously and which required scaffolding through activating features. The second cycle indicated that the designed activating features could indeed scaffold the intended processes. We discuss how this design research specification approach for content-specifically focused scaffolds could be transferred to other subject-matter content.