Phonetic complexity affects children's Mandarin tone production accuracy in disyllabic words: A perceptual study

Focus-marking in a tonal language: Prosodic differences between Cantonese-speaking children with and without autism spectrum disorder

Abnormal speech prosody has been widely reported in individuals with autism. Many studies on children and adults with autism spectrum disorder speaking a non-tonal language showed deficits in using prosodic cues to mark focus. However, focus marking by autistic children speaking a tonal language is rarely examined. Cantonese-speaking children may face additional difficulties because tonal languages require them to use prosodic cues to achieve multiple functions simultaneously such as lexical contrasting and focus marking. This study bridges this research gap by acoustically evaluating the use of Cantonese speech prosody to mark information structure by Cantonese-speaking children with and without autism spectrum disorder. We designed speech production tasks to elicit natural broad and narrow focus production among these children in sentences with different tone combinations. Acoustic correlates of prosodic focus marking like f0, duration and intensity of each syllable were analyzed to examine the effect of participant group, focus condition and lexical tones. Our results showed differences in focus marking patterns between Cantonese-speaking children with and without autism spectrum disorder. The autistic children not only showed insufficient on-focus expansion in terms of f0 range and duration when marking focus, but also produced less distinctive tone shapes in general. There was no evidence that the prosodic complexity (i.e. sentences with single tones or combinations of tones) significantly affected focus marking in these autistic children and their typically-developing (TD) peers.

Production of Tone 2 in disyllabic words in Mandarin Chinese speaking children aged 3-5 with a cochlear implant and a contralateral hearing aid

To investigate Mandarin Tone 2 production of disyllabic words of prelingually deafened children with a cochlear implant (CI) and a contralateral hearing aid (HA) and to evaluate the relationship between their demographic variables and tone-production ability. Thirty prelingually Mandarin-speaking preschoolers with CI+HA and 30 age-matched normal-hearing (NH) children participated in the study. Fourteen disyllabic words were recorded from each child. A total of 840 tokens (14 × 60) were then used in tone-perception tests in which four speech therapists participated. The production of T2-related disyllabic words of the bimodal group was significantly worse than that of the NH group, as reflected in the overall accuracy (88.57% ± 16.31% vs 99.29% ± 21.79%, p < 0.05), the accuracy of T1+T2 (93.33% vs 100%), the accuracy of T2+T1 (66.67 ± 37.91% vs 98.33 ± 9.13%), and the accuracy of T2+T4 (78.33 ± 33.95% vs 100%). In addition, the bimodal group showed significantly inferior production accuracy of T2+T1 than T2+T2 and T3+T2, p < 0.05. Both bimodal age and implantation age were significantly negatively correlated with the overall production accuracy, p < 0.05. For the error patterns, bimodal participants experienced more errors when T2 was in the first position of the tone combination, and T2 was most likely to be mispronounced as T1 and T3. Bimodal patients aged 3-5 have T2-related disyllabic lexical tone production defects, and their performances are related to tone combination, implantation age, and bimodal age.

Motor constellation theory: A model of infants' phonological development

Every normally developing human infant solves the difficult problem of mapping their native-language phonology, but the neural mechanisms underpinning this behavior remain poorly understood. Here, motor constellation theory, an integrative neurophonological model, is presented, with the goal of explicating this issue. It is assumed that infants' motor-auditory phonological mapping takes place through infants' orosensory "reaching" for phonological elements observed in the language-specific ambient phonology, via reference to kinesthetic feedback from motor systems (e.g., articulators), and auditory feedback from resulting speech and speech-like sounds. Attempts are regulated by basal ganglion-cerebellar speech neural circuitry, and successful attempts at reproduction are enforced through dopaminergic signaling. Early in life, the pace of anatomical development constrains mapping such that complete language-specific phonological mapping is prohibited by infants' undeveloped supralaryngeal vocal tract and undescended larynx; constraints gradually dissolve with age, enabling adult phonology. Where appropriate, reference is made to findings from animal and clinical models. Some implications for future modeling and simulation efforts, as well as clinical settings, are also discussed.

Musicality and Age Interaction in Tone Development

Vocal pitch, which involves not only F0 but also multiple covarying acoustic cues is central to linguistic perception and production at various levels of prosodic structure. Recent studies on language development have shown that differences in learners' musicality affect the F0 cue development in perception of sentence-level intonation or in prosodic realization of focus. This study aims to contribute toward a fuller understanding of the effect of musicality on linguistic pitch development via a close investigation of the relationship between musicality, age, and lexical tone production covering both F0 and spectral cues in children. Forty-three native Mandarin-speaking children between the ages of 4 and 6 years are recruited to participate in both a semi-spontaneous tone production task and a musicality test. For each age (4, 5, and 6 years) and musicality (below or above the median score of each age group) group, the contrastivity of the four tones is evaluated by performing automatic tone classification using three sets of acoustic cues (F0, spectral cues, and both). It has been found that higher musicality is associated with higher contrastivity of the tones produced at the age of 4 and 5 years, but not at the age of 6 years. These results suggest that musicality promotes earlier development of tone production only in earlier stages of prosodic development; by the age of 6 years, the musicality advantage in tone production subsides.

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.

The Relative Weight of Temporal Envelope Cues in Different Frequency Regions for Mandarin Disyllabic Word Recognition

Objectives

Acoustic temporal envelope (E) cues containing speech information are distributed across all frequency spectra. To provide a theoretical basis for the signal coding of hearing devices, we examined the relative weight of E cues in different frequency regions for Mandarin disyllabic word recognition in quiet.

Design

E cues were extracted from 30 continuous frequency bands within the range of 80 to 7,562 Hz using Hilbert decomposition and assigned to five frequency regions from low to high. Disyllabic word recognition of 20 normal-hearing participants were obtained using the E cues available in two, three, or four frequency regions. The relative weights of the five frequency regions were calculated using least-squares approach.

Results

Participants correctly identified 3.13-38.13%, 27.50-83.13%, or 75.00-93.13% of words when presented with two, three, or four frequency regions, respectively. Increasing the number of frequency region combinations improved recognition scores and decreased the magnitude of the differences in scores between combinations. This suggested a synergistic effect among E cues from different frequency regions. The mean weights of E cues of frequency regions 1-5 were 0.31, 0.19, 0.26, 0.22, and 0.02, respectively.

Conclusion

For Mandarin disyllabic words, E cues of frequency regions 1 (80-502 Hz) and 3 (1,022-1,913 Hz) contributed more to word recognition than other regions, while frequency region 5 (3,856-7,562) contributed little.

Going beyond F0: The acquisition of Mandarin tones

Using a semi-spontaneous speech corpus, we present evidence from computational modelling of tonal productions from Mandarin-speaking children (4- to 11-years old) and adults, showing that children exceed the adult-level tonal distinction at the age of 7 to 8 years using F0 cues, but do not reach the high adult-level distinction using spectral cues even at the age of 10 to 11 years. The difference in the developmental curves of F0 and spectral cues suggests that, in Mandarin tone production, secondary cues continue to develop even after the mastery of primary cues.

Nonword repetition stimuli for Vietnamese-speaking children

Nonword repetition (NWR) has been a widely used measure of language-learning ability in children with and without language disorders. Although NWR tasks have been created for a variety of languages, minimal attention has been given to Asian tonal languages. This study introduces a new set of NWR stimuli for Vietnamese. The stimuli include 20 items ranging in length from one to four syllables. The items consist of dialect-neutral phonemes in consonant-vowel (CV) and CVC sequences that follow the phonotactic constraints of the language. They were rated high on wordlikeness and have comparable position segments and biphone probabilities across stimulus lengths. We validated the stimuli with a sample of 59 typically developing Vietnamese-English bilingual children, ages 5 to 8. The stimuli exhibited the expected age and length effects commonly found in NWR tasks: Older children performed better on the task than younger children, and longer items were more difficult to repeat than shorter items. We also compared different scoring systems in order to examine the individual phoneme types (consonants, vowels, and tones) and composite scores (proportions of phonemes correct, with and without tone). The study demonstrates careful construction and validation of the stimuli, and future directions are discussed.

Testing the Hyperarticulation and Prosodic Hypotheses of Child-Directed Speech: Insights From the Perceptual and Acoustic Characteristics of Child-Directed Cantonese Tones

PURPOSE

The function of child-directed speech has been debated for decades. This study examined the perceptual and acoustic characteristics of child- and adult-directed Cantonese tones to test the hyperarticulation and prosodic hypotheses that have been proposed to account for the acoustic modifications in child-directed speech.

METHOD

Sixty-two mother-child dyads participated in the study. The mothers verbally labeled 30 pictures in monosyllabic isolated words and in the final position of a carrier sentence to the experimenter and their 1- to 5-year-old children. The 8,634 adult- and child-directed productions were low-pass filtered to eliminate lexical information and presented to 5 judges for tone identification. Acoustic analysis was performed on the productions.

RESULTS

Acoustically, child-directed tones were produced with an elevated pitch, and the pitch level decreased as the child's age increased. Acoustic contrasts between phonetically similar and more confusing tones were not enhanced in child-directed speech, and unexpectedly, child-directed tones were identified with a lower accuracy than adult-directed tones. The perceptual errors of child-directed tones mirrored the errors found in identifying tones excised from sentence-final position, which had a pitch-lowering effect on the tones. The lower perceptual accuracy, the lack of enhanced acoustic contrasts in confusing tone pairs, and the similarities in the error patterns in identifying tones in child-directed speech and tones in utterance-final position suggest that the acoustic modifications in child-directed tones are prosodic effects serving pragmatic purposes.

CONCLUSION

The findings reject the hyperarticulation hypothesis and support the prosodic hypothesis of child-directed speech.

Five-Year-olds' Acoustic Realization of Mandarin Tone Sandhi and Lexical Tones in Context Are Not Yet Fully Adult-Like

Large numbers of children around the world are learning tone languages, but few studies have examined the acoustic properties of children's early tone productions. Even more scarce are acquisition studies on tone sandhi, a tone change phenomenon which alters the surface realization of lexical tones. Two studies using perceptual coding report the emergence of lexical tone and tone sandhi at around 2 years (Li and Thompson, 1977; Hua and Dodd, 2000). However, the only acoustic study available shows that 3-year-olds are not yet adult-like in their lexical tone productions (Wong, 2012). This raises questions about when children's productions become acoustically adult-like and how their tone productions differ from those of adults. These questions were addressed in the current study which compared Mandarin-speaking pre-schoolers' (3-5-year-olds) tone productions to that of adults. A picture naming task was used with disyllabic real words familiar to pre-schoolers. Overall children produced appropriate tone contours for all tones, i.e., level for tone 1, rising for tones 2, 3 and full sandhi, falling for tone 4 and half sandhi. However, children's productions were not adult-like for tones 3, 4, and the sandhi forms, in terms of coordinating pitch range, slope and curvature, with little evidence of development across ages. These results suggest a protracted process in achieving adult-like acoustic realization of both lexical and sandhi tones.

Suprasegmental Features Are Not Acquired Early: Perception and Production of Monosyllabic Cantonese Lexical Tones in 4- to 6-Year-Old Preschool Children

PURPOSE

Previous studies reported that children acquire Cantonese tones before 3 years of age, supporting the assumption in models of phonological development that suprasegmental features are acquired rapidly and early in children. Yet, recent research found a large disparity in the age of Cantonese tone acquisition. This study investigated Cantonese tone development in 4- to 6-year-old children.

METHOD

Forty-eight 4- to 6-year-old Cantonese-speaking children and 28 mothers of the children labeled 30 pictures representing familiar words in the 6 tones in a picture-naming task and identified pictures representing words in different Cantonese tones in a picture-pointing task. To control for lexical biases in tone assessment, tone productions were low-pass filtered to eliminate lexical information. Five judges categorized the tones in filtered stimuli. Tone production accuracy, tone perception accuracy, and correlation between tone production and perception accuracy were examined.

RESULTS

Children did not start to produce adultlike tones until 5 and 6 years of age. Four-year-olds produced none of the tones with adultlike accuracy. Five- and 6-year-olds attained adultlike productions in 2 (T5 and T6) to 3 (T4, T5, and T6) tones, respectively. Children made better progress in tone perception and achieved higher accuracy in perception than in production. However, children in all age groups perceived none of the tones as accurately as adults, except that T1 was perceived with adultlike accuracy by 6-year-olds. Only weak association was found between children's tone perception and production accuracy.

CONCLUSIONS

Contradicting to the long-held assumption that children acquire lexical tone rapidly and early before the mastery of segmentals, this study found that 4- to 6-year-old children have not mastered the perception or production of the full set of Cantonese tones in familiar monosyllabic words. Larger development was found in children's tone perception than tone production. The higher tone perception accuracy but weak correlation between tone perception and production abilities in children suggested that tone perception accuracy is not sufficient for children's tone production accuracy. The findings have clinical and theoretical implications.

Mothers do not enhance tonal contrasts in child-directed speech: Perceptual and acoustic evidence from child-directed Mandarin lexical tones

Prosodically, child-directed speech typically has a higher pitch and more varied pitch contours. Studies that have examined acoustic differences between child-directed and adult-directed vowels and consonants have reported mixed results and proposed two hypotheses explaining the function of the acoustic modifications in child-directed speech. The hyperarticulation hypothesis suggests that mothers enhance the phonemic contrasts in child-directed speech to facilitate speech and language acquisition in children. The pragmatic hypothesis claims that the acoustic differences between child-directed and adult-directed speech result from mothers' expression of affective emotions towards young children. In tone languages, pitch is used at the syllable level to make lexical contrasts and at the utterance level to serve pragmatic functions. This study compared the perceptual clarity and acoustic characteristics of adult-directed and child-directed Mandarin tones to test the two hypotheses. 1648 child-directed and adult-directed tones produced by 20 mothers in monosyllabic and disyllabic words were low-pass filtered to eliminate segmental information and presented to five judges for tone identification. Child-directed tones were identified with poorer accuracy than adult-directed tones. Acoustic analysis revealed that child-directed tones, regardless of tone type, were produced with higher pitch and more positive slopes than adult-directed tones. The findings did not support the hyperarticulation hypothesis.

Acoustic characteristics of highly distinguishable Cantonese entering and non-entering tones

Cantonese has one of the most complex tone systems. Few studies have thoroughly examined or compared the acoustic properties of the full set of Cantonese tones, particularly the entering tones, compromising deeper understanding of Cantonese tone difficulties in various clinical populations. This study (1) describes a theory-driven method for acoustic analysis of tones that successfully normalized the intrinsic pitch of male and female speakers, (2) provides detailed acoustic data on distinctly enunciated Cantonese tones, (3) examines the acoustic similarities and differences between the entering and non-entering tones, and (4) compares the acoustic properties of three easily confused tone pairs. Seventeen male and female native speakers produced 1802 Cantonese tones that were correctly identified by five judges in filtered stimuli. Counter to the established notion that the entering tones are shorter versions of the three level tones, the results revealed that the entering tones have falling contours, suggesting that the entering and non-entering tones should be examined separately in research and clinical settings. The detailed description of the acoustic properties of the nine tones and the acoustic contrasts of the entering and non-entering tones and the three easily confused tone pairs provides references for future Cantonese tone studies with different populations.

Cantonese-Speaking Children Do Not Acquire Tone Perception before Tone Production-A Perceptual and Acoustic Study of Three-Year-Olds' Monosyllabic Tones

Models of phonological development assume that speech perception precedes speech production and that children acquire suprasegmental features earlier than segmental features. Studies of Chinese-speaking children challenge these assumptions. For example, Chinese-speaking children can produce tones before two-and-a-half years but are not able to discriminate the same tones until after 6 years of age. This study compared the perception and production of monosyllabic Cantonese tones directly in 3 -year-old children. Twenty children and their mothers identified Cantonese tones in a picture identification test and produced monosyllabic tones in a picture labeling task. To control for lexical biases on tone ratings, the mother- and child-productions were low-pass filtered to eliminate lexical information and were presented to five judges for tone classification. Detailed acoustic analysis was performed. Contrary to the view that children master lexical tones earlier than segmental phonemes, results showed that 3-year-old children could not perceive or produce any Cantonese tone with adult-like proficiency and incorrect tone productions were acoustically different from criterion. In contrast to previous findings that Cantonese-speaking children mastered tone production before tone perception, we observed more accuracy during speech perception than production. Findings from Cantonese-speaking children challenge some of the established tenets in theories of phonological development that have been tested mostly with native English speakers.