Functional Diversification and Progressive Routinization of a Multiword Expression in and for Social Interaction: A Longitudinal L2 Study

In this article, we bring together conversation analysis and usage‐based linguistics to investigate the second language (L2) developmental trajectory of a linguistic construction within the complex multimodal ecology of naturally occurring social interaction. We document how, over the course of 15 months, an L2 speaker's use of the French multiword expression comment on dit [how do you say] diversifies in both form and function. Two types of longitudinal change are observed: (a) The expression expands in its context of use: “Literal” uses are observed initially to request a candidate lexical item but are later also found in requests for confirmation, (b) these literal uses become proportionally less frequent, and the expression progressively routinizes as a marker‐like element used for indexing cognitive search and floor‐holding, and eventually also as a preface to self‐correction. This routinization entails erosion in form and meaning, in concert with systematic change in co‐occurring bodily‐visual conduct, in particular gaze and gesture. By documenting change over time in the functional use and the multimodal delivery of the target construction, the findings evidence the longitudinal development of L2 grammar‐for‐interaction and showcase how linguistic and bodily resources may interface in L2 development. They also have important implications for language teaching and learning.