Extracting Phonetic Features From Natural Classes: A Mismatch Negativity Study of Mandarin Chinese Retroflex Consonants

Abstract

How speech sounds are represented in the brain is not fully understood. The mismatch negativity (MMN) has proven to be a powerful tool in this regard. The MMN event-related potential is elicited by a deviant stimulus embedded within a series of repeating standard stimuli. Listeners construct auditory memory representations of these standards despite acoustic variability. In most designs that test speech sounds, however, this variation is typically intra-category: All standards belong to the same phonetic category. In the current paper, inter-category variation is presented in the standards. These standards vary in manner of articulation but share a common phonetic feature. In the standard retroflex experimental block, Mandarin Chinese speaking participants are presented with a series of “standard” consonants that share the feature [retroflex], interrupted by infrequent non-retroflex deviants. In the non-retroflex standard experimental block, non-retroflex standards are interrupted by infrequent retroflex deviants. The within-block MMN was calculated, as was the identity MMN (iMMN) to account for intrinsic differences in responses to the stimuli. We only observed a within-block MMN to the non-retroflex deviant embedded in the standard retroflex block. This suggests that listeners extract [retroflex] despite significant inter-category variation. In the non-retroflex standard block, because there is little on which to base a coherent auditory memory representation, no within-block MMN was observed. The iMMN to the retroflex was observed in a late time-window at centro-parieto-occipital electrode sites instead of fronto-central electrodes, where the MMN is typically observed, potentially reflecting the increased difficulty posed by the added variation in the standards. In short, participants can construct auditory memory representations despite significant acoustic and inter-category phonological variation so long as a shared phonetic feature binds them together.

Unified Coding of Spectral and Temporal Phonetic Cues: Electrophysiological Evidence for Abstract Phonological Features

“…This is especially relevant in designs where asymmetric responses are predicted, as in the current experiment. Second, the responses in the late time-window here are consistent with previous findings (Fu & Monahan, 2021). There, the deviant in the underspecified standard block elicited a positivity in the ~300 ms -ms time-window, and the deviant in the specified standard block elicited a negativity in a similar time-window.…”

“…Similar experiments testing phonetic and phonological representations have also reported the iMMN (Cornell et al, 2011(Cornell et al, , 2013Fu & Monahan, 2021;Hestvik & Durvasula, 2016). In the current iMMN analysis, the ERP to the voiced deviants was more negative relative to the ERP to the voiced standards around 200 ms post-stimulus onset.…”

“…The timing and distribution of the larger negativity to the voiced deviants are consistent with previous MMN reports (Näätänen et al, 2007). The larger positivity to the voiceless deviants in the voicedstandard block is not likely an MMN, but is also consistent with previous reports that have used an inter-category variation many-to-one oddball paradigm for the unmarked standards (Fu & Monahan, 2021).…”

“…Negative deflections in this study also occurred around 316 ms -440 ms post-stimulus onset, which is later than the normal MMN window (Čeponienė et al, 2002;Cheour et al, 2001;Martynova et al, 2003;Strotseva-Feinschmidt et al, 2015). Late negativities have been observed in both speech (Datta et al, 2020;Fu & Monahan, 2021;Hestvik & Durvasula, 2016) and non-speech paradigms (Peter et al, 2012;Zachau et al, 2005). These late negativities typically appear with the traditional MMN but can also appear independently (Strotseva-Feinschmidt et al, 2015).…”

“…As noted above, Fu and Monahan (2021) also report an asymmetric MMN with inter-category variation in the standards but tested retroflex consonants in Mandarin Chinese. There, Mandarin speaking participants were exposed to inter-category variation in the standards.…”