Abstract
Abstract Background In the age of rapid scientific and technological advancement, cultivating primary students’ scientific inquiry competence has become an educational priority. STEM project-based learning (STEM PBL) offers an authentic context for inquiry, yet its open-ended tasks often require students to coordinate multiple resources across inquiry steps. This can fragment attention, undermine motivation following unsuccessful inquiry attempts, and leave students unsure how to organize the inquiry process. To address these challenges, this study developed a digital metaphor game-mediated STEM PBL (DMG-STEM PBL) approach. Specifically, a front-loaded digital metaphor game was used as a mediating scaffold to introduce a metaphorical inquiry framework, which was then reinforced through metaphor-recall prompts and metaphor-supported reflective narration during STEM project work. Results A quasi-experimental study was conducted to examine its effects on primary students’ perceived scientific inquiry competence, learning experience (including learning motivation and flow experience), and cognitive load. Two sixth-grade classes were randomly assigned at the class level to the experimental group (N = 48), which adopted the DMG-STEM PBL approach, or the control group (N = 42), which used conventional STEM PBL. Results showed that students in the DMG-STEM PBL group reported significantly higher scores on overall perceived scientific inquiry competence and on the dimensions of planning, experimenting and data collection, and analyzing and concluding. They also reported greater learning motivation and flow experience. For cognitive load, students in the DMG-STEM PBL group reported higher overall cognitive load, with higher mental effort but no significant between-group difference in mental load. Conclusions These findings provide insights and practical implications for future research on STEM PBL instruction and the development of primary students’ scientific inquiry competence.