Alignment to a Mandarin Target Correlates With Talker Discrimination Ability in Tibetan-Mandarin Bilinguals

Extracting talker identity from speech signals is a core perceptual function, yet the mechanisms underlying second Language (L2) identity processing remain unclear. Grounded in the DIVA model and Source-Filter Theory, this study investigated the coupling between perception and production in Tibetan-Mandarin bilinguals. Participants performed a delayed imitation task and a talker-identity discrimination task. Imitation performance was quantified within a multidimensional acoustic space defined by fundamental frequency (F0), harmonics-to-noise ratio (HNR), and formant dispersion (FD). Results indicated that learners achieved significant acoustic convergence toward the L2 model speaker, which persisted as episodic traces across short-term temporal delays. In the discrimination task, sensitivity improved with acoustic distance but plateaued between medium and large distances, while a significant negative response bias in the near condition revealed a tendency toward perceptual assimilation. Crucially, regression and machine-learning analyses revealed that only FD distance was significantly associated with discrimination sensitivity. Unlike source-related cues such as F0 that fluctuate with context, FD reflects relatively invariant vocal-tract structures. These findings suggest that the formation of L2 talker-identity representations involves a functional anatomical alignment with the target speaker through sensorimotor inverse mapping. By locking onto structural invariants like FD, learners can overcome within-person variability to form detailed episodic identity representations. This study extends the scope of auditory targets in speech production models from segmental to indexical levels.