Topic shifting (Iawasaki, 1997; Jefferson, 1993; Maynard, 1980; Morris-Adams, 2014; West & Garcia, 1988) is an activity collaboratively done by both the current speaker and the hearer. The present study will examine various ways in which two American students who are taking the same Japanese courses during their study abroad in Japan shift topics in their informal conversations that they video-recorded four times during a period of four months, and explore any changes found in their collaborative topic shifting during the period.

While research on interactional competences of second language (L2) speakers tend to focus on one L2 speaker’s competence, the present study will analyze topic shifting as a collaborative activity and uncover a range of ways in which the two L2 speakers contribute to topic shifting, from an abrupt change of topics of after a long moment of silence to smooth transition between related topics. Through the analysis of longitudinally collected data, it will reveal the aspects of L2 speakers’ interactional competences that are co-constructed, affect each other, and change over time as they develop their relationship with each other.