Prosodic hierarchy and the encoding of modality: a study of L2 French statements and commands by Mandarin learners

The interface between lexical tone and phrase-level intonation constitutes a complex functional interface constraint in Second Language Acquisition (SLA). This study investigates the acquisition of French prosody by Mandarin learners (n = 35) at two proficiency levels compared to a native baseline (n = 8), identifying a developmental dissociation between structural and pragmatic functions. Utilizing Linear Mixed-Effects Models (LMM), we analyzed four acoustic parameters-Global Pitch Span, Final Pitch Span, Final Expansion, and Final Lengthening-across a factorial design crossing modality (Statement vs. Command) and utterance length. The results reveal a bifurcated acquisition trajectory: while intermediate learners demonstrate convergence toward native-like macro-prosodic framing (successfully expanding global pitch envelopes for structural demarcation), they reach a persistent plateau in micro-prosodic pragmatic encoding. Specifically, learners failed to implement the sharp nuclear reshaping and pitch intensification required to signal directive force, resulting in a systematic "prosodic merging" of modalities. Based on these findings, we propose the Modality-Prosody Acquisition Hierarchy (MPAH), which posits that the automation of a stable structural frame (Tier 2) serves as a functional prerequisite for the high-resolution modulation of illocutionary intent (Tier 3). These findings refine the Prosodic Transfer Hypothesis by isolating the selective processing constraints at the tone-to-intonation transition and offer a tiered roadmap for pedagogical intervention.