Developing Students' Spatial Thinking through Culture-Based Geometry Learning: A Qualitative Analysis of Van Hiele Theory and Problem-Based Learning

Spatial thinking is fundamental to geometry learning, yet classroom instruction often provides limited opportunities for students to develop meaningful spatial representations. This study explored how geometry learning integrating Nias cultural contexts, Problem-Based Learning (PBL), and instructional principles derived from Van Hiele's theory facilitated students' spatial thinking. A qualitative case study was conducted with 24 eighth-grade students in Indonesia. Data were collected through classroom observations, spatial ability tasks, and semi-structured interviews and analysed using the interactive model of Miles, Huberman, and Saldaña (2014), supported by data triangulation. The findings revealed a progressive development of students' spatial thinking. Students initially constructed visual representations of geometric objects, then coordinated spatial relationships within composite solids, and ultimately integrated multiple representations of transformed three-dimensional objects. Authentic cultural artefacts provided meaningful visual contexts, while PBL and Van Hiele-guided instruction supported collaborative inquiry and the progressive refinement of spatial reasoning. Interview findings corroborated the patterns identified in students' written responses, strengthening the credibility of the findings. This study contributes a pedagogical framework demonstrating how culturally responsive geometry learning, structured through PBL and guided by Van Hiele's instructional principles, can foster the progressive development of students' spatial thinking and provide practical guidance for designing meaningful geometry instruction.