Collective Spatial Interaction for Immersive Museum Storytelling: The MEI (Museo Egizio Interattivo) Experience

Immersive museum installations rely on pre-authored cinematic content or on interaction mediated by individual devices. Interactive storytelling adds visitor agency, but at the individual level. This paper investigates collective spatial interaction for device-free group agency through MEI (Museo Egizio Interattivo), a collective experience for the immersive room of Museo Egizio. During the experience, visitors drive a branching story by standing in floor zones while a Stage Manager aggregates their positions to select the next branch. The narrative is authored by museum curators with LLM assistance. A pilot with 30 participants reports high involvement, agency, and user experience, with moderate general and spatial presence. Cross-session differences hint at a possible effect of group size and composition on spatial presence, though limited by sample size. Qualitative responses reveal a trade-off between session-completion safeguards (the RetryScene recovery) and perceived freedom. The findings carry design implications for choice resolution, narrative recovery, and group configuration.