Interlanguage pragmatics (Kasper & Blum-Kulka, 1993) is a research area that is concerned with what second language (L2) learners do with the target language, and how their competence in using the language develops

over time. However, until 1996 when Kasper and Schmidt put out agendas for more developmentally oriented investigations, research on interlanguage pragmatics had been predominated by studies focusing on the former, L2 use at a point in time. This research area has matured more by now in the area of developmental interlanguage pragmatics, as reviewed in Kasper and Rose (2002). Along with an increased attention to longitudinal development arose investigation of the role of interaction, as well as the role of instruction, in L2 pragmatic development. Taking Schieffelin and Ochs’ (1986) language socialization theory (e.g., DuFon, 1999) and Vygotsky’s theory of psychological and language development (e.g., Belz & Kinginger, 2003; Ohta, 2001), researchers have recently began exploring the affordances of social interaction for emergent competence and longitudinal development. In this paper, I will further this line of research with a focus on the examination of microgenesis (Vygotsky, 1979; Wertsch & Stone, 1978) of modal expressions in decision-making activities between a native speaker and an L2 learner of Japanese.