Chao Han

Mismatch negativity arises from the construction of a memory trace encoding regularities extracted from auditory stimuli in an oddball paradigm. A previous study argued that when phonetic standards are varied within the limits of a phoneme category (i.e., the mental representation of speech sounds), the auditory cortex retrieves a discrete phoneme representation from long‐term memory and uses it as the memory trace for deviance detection. This claim has motivated a body of work using varying‐standards paradigms to probe phonological underspecification. A strong version of this claim predicts that varying standards should eliminate mismatch negativity when both standards and deviants belong to the same phoneme category, because the memory trace is purely phonemic and lacks acoustic detail. We tested this prediction in three electroencephalography experiments using English /t/ varying in voice onset time. In Experiment 1, a within‐category deviant with a long voice onset time elicited a robust mismatch negativity even when standards varied across shorter values, contrary to the prediction of an exclusively symbolic phoneme‐based memory trace. Experiments 2 and 3 further examined whether the within‐category mismatch response reflects long‐term memory representations of phonetic realizations associated with the evoked phoneme category or listeners' ad hoc representation of the stimulus distribution. The weight of the evidence suggests that the within‐category mismatch negativity in the varying‐standards paradigm reflects sensitivity to the statistical structure of the stimulus physical properties, rather than exclusive access to abstract phonological categories. Findings invite reinterpretation of studies using varying‐standards paradigm in light of encoding of stimulus statistics.

Background: Accented speech contains talker-indexical cues that listeners can use to infer social group membership, yet it remains unclear how the auditory system categorizes accent variability and how this process depends on language experience. Methods: The current study used EEG and the MMN oddball paradigm to test pre-attentive neural sensitivity to accent changes of English words stopped produced by Canadian English or Mandarin Chinese-accented English talkers. Three participant groups were tested: Native English listeners, L1-Mandarin listeners, and Heritage Mandarin listeners. Results: In the Native English and L1-Mandarin groups, we observed MMNs to the Canadian accented English deviant, indicating that the brain can group speech by accent despite substantive inter-talker variation and that this grouping is consistent with an experience-dependent sensitivity to accent. Exposure to Mandarin Chinese-accented English modulated MMN magnitude. Time-frequency analyses suggested that α and low-β power during accent encoding varied with language background, with Native English listeners showing stronger activity when presented with Mandarin Chinese-accented English. Finally, the neurophysiological response in the Heritage Mandarin group reflected a broader phonological space encompassing both Canadian English and Mandarin-accented English, and its magnitude was predicted by Chinese proficiency. Conclusions: These findings provide brain-based evidence that automatic accent categorization is not uniform across listeners but interacts with native phonology and second-language experience.

Accented speech contains talker-indexical cues that listeners can use to infer social group membership, yet it remains unclear how the auditory system categorizes accent variability and how this process depends on language experience. The current study used EEG and the MMN oddball paradigm to test pre-attentive neural sensitivity to accent changes of English words stopped produced by Canadian English or Mandarin Chinese accented English talkers. Three participant groups were tested: Native English listeners, L1-Mandarin listeners, and Heritage Mandarin listeners. In the Native English and L1-Mandarin groups, we observed MMNs to the Canadian accented English deviant, indicating that the brain can group speech by accent despite substantive inter-talker variation and is consistent with an experience-dependence sensitivity to accent. Exposure to Mandarin Chinese accented English modulated MMN magnitude. Time-frequency analyses suggested that α and low-β power during accent encoding varied with language background, with Native English listeners showing stronger activity when presented with Mandarin Chinese accented English. Finally, the neurophysiological response in the Heritage Mandarin group reflected a broader phonological space encompassing both Canadian English and Mandarin-accented English, and its magnitude was predicted by Chinese proficiency. These findings provide brain-based evidence that automatic accent categorization is not uniform across listeners but interacts with native phonology and second-language experience.

The impact of corrective feedback explicitness on second language acquisition remains a critical area of inquiry, yet research on classroom-based learning of Mandarin tones – particularly challenging for first language (L1) English speakers – remains scarce. Furthermore, most feedback studies are conducted in laboratory settings, which may not reflect real-world second language (L2) classroom learning. The few classroom-based studies that exist often lack internal validity, such as failing to include a control group. Additionally, individual learner differences are rarely considered when investigating feedback effectiveness. To address these gaps, this study compares the effectiveness of two feedback types – recasts and metalinguistic feedback – in U.S. university students’ learning of Chinese tones within an online communicative classroom environment. It also examines whether feedback effects are modulated by learners’ explicit knowledge of vocabulary tone values and working memory capacities. Forty-eight novice learners of Chinese were assigned to three groups (recasts, metalinguistic feedback, control) and completed an online synchronous course comprising four 65–85-minute sessions over two weeks. Feedback effects were assessed through controlled (sentence reading) and spontaneous (picture description) oral production tasks administered before, immediately after, and two weeks post-treatment. Phonological short-term memory was evaluated via a nonword recall test, while executive working memory was measured with a listening span test. Results revealed that recasts produced larger and more sustainable gains than metalinguistic feedback, particularly in spontaneous tone use. While phonological short-term memory had minimal impact, executive working memory predicted pretreatment tone accuracy and enhanced the effects of recasts but was negatively associated with the utility of metalinguistic feedback. Vocabulary tone knowledge was linked to pretreatment tone accuracy; however, improvements in this knowledge resulting from instruction did not influence feedback effectiveness. This study highlights the efficacy of recasts in Mandarin tone learning, reinforcing the superiority of implicit over explicit metalinguistic instruction for similar L2 phonological targets.

A critical part of the Mismatch Negativity (MMN) mechanism is the construction of a memory trace encoding regularities extracted from the stimuli in an oddball paradigm. In an influential study, Phillips et al. (2000) argued that varying phonetic standards within the limits of a phoneme category prompts the auditory cortex to access representations of the “discrete phonological categories” (p. 1050), resulting in a mismatch response by comparing the deviant stimulus to an abstract, evoked category representation. The present study tested the strongest interpretation of this claim–namely, that the phoneme itself is retrieved from long-term memory and serves as the memory trace for the stimulus sequence. This interpretation has been the implicit, if not explicit, basis for a body of research employing the varying-standards paradigm to probe phonological underspecification. However, while previous research has focused on contrasts between distinct phonemes, we examined a previously untested prediction of this interpretation: that varying the standards should eliminate the MMN when the contrast is within a single phoneme category. Contrary to this prediction, we observed a mismatch negativity to a within-category deviant even when standards were varied. In two additional experiments we further examined whether the within-category MMN is from long-term memory representations of phonetic realizations of the phoneme, or from listeners constructing ad hoc statistical representations of the stimulus distribution. The weight of the evidence suggests that the within-category MMN observed with varying standards reflects sensitivity to the statistical structure of the stimuli, rather than activation of abstract phonological categories.

Previous ERP studies showed that false affirmative sentences elicited a larger N400 than their true versions, but they found the reverse pattern when the sentences were of negative form as if N400 was blind to negation. This negation-blind N400 pattern arguably constituted evidence for two-step accounts of negation processing: When processing negative sentences, a comprehender first computes an internal proposition and then considers the negation. However, the prior studies were confounded by a lexical priming relation between subject and object. Therefore, it was an open question whether or not the observed ERP pattern really reflected the two-step process. To tackle this question, we conducted an ERP experiment, using size-comparison statements where subjects and objects are semantically unrelated. This design allowed us to remove the priming confound. We predicted that if the previous negation-blind N400 pattern is unrelated to lexical priming, it would be replicated; if not, it would disappear. The result was consistent with the second prediction. This suggests that the previously observed negation-blind N400 pattern does not necessarily constitute evidence for two-step accounts of negation processing.