Individual differences in processing pitch contour and rise time in adults: A behavioral and electrophysiological study of Cantonese tone merging

A New System of Cantonese Tones? Tone Perception and Production in Hong Kong South Asian Cantonese

Studies in language contact have identified many instances of linguistic variation and grammatical innovations introduced by speakers from multi-ethnic urban neighborhoods. This study focuses on the variety of Cantonese spoken by South Asian youths in Hong Kong, specifically their production and perception of Hong Kong Cantonese tones. Our findings show that the South Asian Cantonese speakers have a smaller tonal inventory than the canonical six-tone system of standard Hong Kong Cantonese and their tonal discrimination abilities are also more impoverished relative to their ethnic Chinese peers. Further analysis shows a positive correlation between tonal discrimination accuracy and tonal realization distinctness among the South Asian speakers, but not among the ethnic Chinese. These findings suggest that South Asian Cantonese speakers might have developed a distinct tone system from their ethnic Chinese peers.

Characteristics of Effective Auditory Training: Implications From Two Training Programs That Successfully Trained Nonnative Cantonese Tone Identification in Monolingual Mandarin and Bilingual Mandarin-Taiwanese Tone Speakers

Purpose Auditory training is important in pedagogical and clinical settings. In search of a more effective perceptual program for training new suprasegmental categories, this study examined the effect of two auditory programs that incorporated five elements that have previously been identified to be effective for training nonnative segmental and suprasegmental speech sounds on the identification of a complex foreign lexical tone system (Cantonese) that contrasts both pitch shapes and pitch heights. To investigate the training outcomes in learners with different tonal systems, monolingual Mandarin-speaking learners who have a smaller native tonal system that contrasts pitch shapes only and bilingual Mandarin-Taiwanese-speaking learners who have a larger native tonal system that contrasts both pitch shapes and pitch heights were recruited for training. Method Thirty Mandarin-speaking monolinguals and 33 Mandarin-Taiwanese-speaking bilinguals in Taiwan were randomly assigned to two training programs, one with different tones and the other with the same tone preceding the target words in the same training block, and received six 90-min training sessions within 2 weeks. They took a Cantonese Tone Identification Test before training and after each training session. Twenty Cantonese native speakers in Hong Kong served as the reference group and took the same Cantonese Tone Identification Test. Results The two training programs were equally effective. Before training, the monolinguals performed poorer than the bilinguals. After training, the monolinguals and bilinguals in both training programs identified the six Cantonese tones in new words, new utterances, and novel speakers with comparable results, and their overall accuracy did not differ from that of the Cantonese native speakers. Conclusions Though learners with a larger and more complex native tonal system have initial advantage in learning nonnative tones, the intensive high-variability full-set training programs that provide explicit phonetic instruction and contrastive feedback of nonnative tones effectively promote nonnative tone acquisition in learners of different tone languages. The findings revealed factors affecting nonnative tone acquisition in tone speakers. The design of the two programs can be adopted in future programs for effective auditory training of segmental and suprasegmental speech sounds.

Dissociation of tone merger and congenital amusia in Hong Kong Cantonese

While the issue of individual variation has been widely studied in second language learning or processing, it is less well understood how perceptual and musical aptitude differences can explain individual variation in native speech processing. In the current study, we make use of tone merger in Hong Kong Cantonese, an ongoing sound change that concerns the merging of tones in perception, production or both in a portion of native speakers, to examine the possible relationship between tone merger and musical and pitch abilities. Although a previous study has reported the occurrence of tone merger independently of musical training, it has not been investigated before whether tone-merging individuals, especially those merging tones in perception, would have inferior musical perception and fine-grained pitch sensitivities, given the close relationship of speech and music. To this end, we tested three groups of tone-merging individuals with various tone perception and production profiles on musical perception and pitch threshold tasks, in comparison to a group of Cantonese speakers with congenital amusia, and another group of controls without tone merger or amusia. Additionally, the amusics were compared with tone-merging individuals on the details of their tone discrimination and production profiles. The results showed a clear dissociation of tone merger and amusia, with the tone-merging individuals exhibiting intact musical and pitch abilities; on the other hand, the amusics demonstrated widespread difficulties in tone discrimination yet intact tone production, in contrast to the highly selective confusion of a specific tone pair in production or discrimination in tone-merging individuals. These findings provide the first evidence that tone merger and amusia are distinct from each other, and further suggest that the cause of tone merger may lie elsewhere rather than being driven by musical or pitch deficits. We also discussed issues arising from the current findings regarding the neural mechanisms of tone merger and amusia.

Top-down and bottom-up mechanisms as reflected by beta and gamma oscillations in speech perception: An individual-difference approach

Recent neurophysiological studies have proposed distinct roles of β and γ oscillations in implementing top-down and bottom-up processes. The present study aims to test this hypothesis in the domain of speech perception. We examined β and γ oscillations elicited to a tone contrast in a passive oddball paradigm, and their relationships with discrimination sensitivity d' and RT from two groups of healthy adults who showed high and low discrimination sensitivity to the contrast. The low-sensitivity group showed a significant reduction in β, which was further related to d'. Individual differences in RT were related to different frequency bands in the two groups, with a RT-β correlation in the low-sensitivity group, and a RT-γ relation in the high-sensitivity group. Based on these findings, we suggest that β, implicated in top-down processing, reflects individual differences in phonological representations, and that γ, involved in bottom-up processing, reflects individual differences in acoustic encoding.

Induced gamma oscillations index individual differences in speech sound perception and production

Auditory neuroscience has provided strong evidence that neural oscillations synchronize to the rhythm of speech stimuli, and oscillations at different frequencies have been linked to processing of different language structures. The present study aims to examine how these ubiquitous neurophysiological attributes may inform us about the brain processes that underpin individual differences in speech perception and production, which in turn elucidate the specific functions of neural oscillations in the domain of speech processing. To this end, we recorded electrophysiological responses to a lexical tone contrast in a passive auditory oddball paradigm from two groups of healthy tone-language speakers who were equal in perceptual discriminability but differed in response latency and production distinctiveness of the tone contrast. Time-frequency analysis was applied to the EEG data, and decomposed into theta (4-7 Hz), beta (12-30 Hz), and gamma (30-50 Hz) frequency bands. Results show that listeners with longer discrimination RT and less distinctive production showed significantly higher induced (non-phase-locked) gamma during tone processing. Moreover, among speakers with less distinctive production, individual differences in induced gamma were significantly correlated with discrimination latency and production distinction. Based on the present findings, we propose that differences in gamma oscillations reflect differential sensory/perceptual computations during acoustic encoding, impacting the quality of perceptual representations, which further mediates individual differences in speech perception and production.

Cognitive basis of individual differences in speech perception, production and representations: The role of domain general attentional switching

This study investigated whether individual differences in cognitive functions, attentional abilities in particular, were associated with individual differences in the quality of phonological representations, resulting in variability in speech perception and production. To do so, we took advantage of a tone merging phenomenon in Cantonese, and identified three groups of typically developed speakers who could differentiate the two rising tones (high and low rising) in both perception and production [+Per+Pro], only in perception [+Per-Pro], or in neither modalities [-Per-Pro]. Perception and production were reflected, respectively, by discrimination sensitivity d' and acoustic measures of pitch offset and rise time differences. Components of event-related potential (ERP)-the mismatch negativity (MMN) and the ERPs to amplitude rise time-were taken to reflect the representations of the acoustic cues of tones. Components of attention and working memory in the auditory and visual modalities were assessed with published test batteries. The results show that individual differences in both perception and production are linked to how listeners encode and represent the acoustic cues (pitch contour and rise time) as reflected by ERPs. The present study has advanced our knowledge from previous work by integrating measures of perception, production, attention, and those reflecting quality of representation, to offer a comprehensive account for the underlying cognitive factors of individual differences in speech processing. Particularly, it is proposed that domain-general attentional switching affects the quality of perceptual representations of the acoustic cues, giving rise to individual differences in perception and production.