What Changes When the Interlocutor Is an AI? Interactional Fluency and Linguistic Uptake in L2 Spoken Dialogue
For L2 learners and educators, the study reveals complementary affordances of AI and human dialogue partners, informing design of AI-based speaking practice tools.
The study compared L2 spoken dialogue with a human peer versus an AI partner, finding that AI dialogue resembled supported monologue with greater short-term linguistic uptake and syntactic priming, while human dialogue was faster and more balanced.
Voice-based AI systems are increasingly used for L2 speaking practice, but evaluations rarely characterize the interactional processes they create. We analyze 78 university learners of German across four sites completing a counterbalanced spot-the-difference task with both a human peer and a real-time AI partner. From diarized ASR transcripts, we extract measures of interactional fluency, linguistic uptake, and learner experience. Human dialogue was faster and more balanced, with many short turns; AI dialogue resembled supported monologue, with fewer, longer turns, reduced learner floor share, and greater within-turn fluency. The AI's verbose, syntactically regular input was associated with greater short-term uptake and stronger syntactic priming after controlling for input volume. Attitudes toward AI improved after the task, and satisfaction was predicted by production fluency rather than uptake. The results show complementary affordances for AI and human dialogue in L2 practice.