Dynamic insights into incomplete neutralisation in Beijing Mandarin: retroflex suffixation and rime merger through GAMM analyses

Incomplete neutralisation (IN), wherein phonologically neutralised categories yield phonetically non-neutralising outputs, has been documented in a variety of languages. Frequently-discussed evidence includes American /t/-flapping (Braver, 2014) and German final devoicing (Oostendorp, 2008). This study examines IN in Beijing Mandarin (BM) through retroflex suffixation (BRS) using generalised additive mixed models (GAMMs, Hastie & Tibshirani, 1986). In BRS, an [ɚ] suffix denotes diminutiveness, altering rime quality and potentially merging phonological contrasts. A production experiment was conducted with 11 native BM speakers producing 136 rime pairs, both suffixed and unsuffixed. Acoustic data, including formant frequencies and F0 values, were extracted at 21 equidistant points of rime course and analysed through GAMMs, with 77 models fitted to capture dynamic changes across rime and tonal conditions. The findings indicate that BRS induces significant spectral alterations across rimes, with varying degrees of vowel raising, lowering, or retraction. Low-nuclear vowels like [a], [ai], and [an] merge fully after suffixation, while high-nuclear rime groups with [i] and [y] nuclei show partial merger. Mid-nuclear vowel [ɤ] remains distinct after suffixation. Tone contours are preserved, though F0 values generally decrease. Such phonetic incompleteness or gradience challenges the assumption that phonologically-neutralised contrast, which is categorical, should not yield gradient surface distinctions. Therefore, it poses challenges to the traditional modular feed-forward phonology-phonetics interface (Bermúdez-Otero, 2007; Chomsky & Halle, 1991; Kenstowicz, 1994; Pierrehumbert, 2002), which posits that phonetics only has access to the discrete phonological output that does not contain any gradient phonetic information.