"Left to myself, I wouldn’t have done it”: Dagen H in mathematics education.

This paper investigates how undergraduate mathematics students negotiate their identities within a collaborative problem-solving activity structured around assigned roles. Drawing on the metaphor of Dagen H—the day Sweden transitioned from left- to right-hand traffic—the study investigates what occurs when students are invited to engage in unfamiliar forms of mathematical participation. Students were assigned one of three roles—Narrator, Participant, or Specialist—each representing a different way of engaging in and talking about mathematics. By analyzing group-written reports alongside follow-up interviews, the study examines how students enact these roles and narrate their experiences. Findings highlight the interplay between role enactment and self-narration, showing how the role structure invites students to explore alternative ways of participating in mathematics and articulate who they might become within the discipline.