Spoken Language Development and the Challenge of Skill Integration

Exposure to Canadian French Cued Speech Improves Consonant Articulation in Children With Cochlear Implants: Acoustic and Articulatory Data

PURPOSE

One of the strategies that can be used to support speech communication in deaf children is cued speech, a visual code in which manual gestures are used as additional phonological information to supplement the acoustic and labial speech information. Cued speech has been shown to improve speech perception and phonological skills. This exploratory study aims to assess whether and how cued speech reading proficiency may also have a beneficial effect on the acoustic and articulatory correlates of consonant production in children.

METHOD

Eight children with cochlear implants (from 5 to 11 years of age) and with different receptive proficiency in Canadian French Cued Speech (three children with low receptive proficiency vs. five children with high receptive proficiency) are compared to 10 children with typical hearing (from 4 to 11 years of age) on their production of stop and fricative consonants. Articulation was assessed with ultrasound measurements.

RESULTS

The preliminary results reveal that cued speech proficiency seems to sustain the development of speech production in children with cochlear implants and to improve their articulatory gestures, particularly for the place contrast in stops as well as fricatives.

CONCLUSION

This work highlights the importance of studying objective data and comparing acoustic and articulatory measurements to better characterize speech production in children.

Phoneme Representation and Articulatory Impairment: Insights from Adults with Comorbid Motor Coordination Disorder and Dyslexia

Phonemic processing skills are impaired both in children and adults with dyslexia. Since phoneme representation development is based on articulatory gestures, it is likely that these gestures influence oral reading-related skills as assessed through phonemic awareness tasks. In our study, fifty-two young dyslexic adults, with and without motor impairment, and fifty-nine skilled readers performed reading, phonemic awareness, and articulatory tasks. The two dyslexic groups exhibited slower articulatory rates than skilled readers and the comorbid dyslexic group presenting with an additional difficulty in respiratory control (reduced speech proportion and increased pause duration). Two versions of the phoneme awareness task (PAT) with pseudoword strings were administered: a classical version under time pressure and a delayed version in which access to phonemic representations and articulatory programs was facilitated. The two groups with dyslexia were outperformed by the control group in both versions. Although the two groups with dyslexia performed equally well on the classical PAT, the comorbid group performed significantly less efficiently on the delayed PAT, suggesting an additional contribution of articulatory impairment in the task for this group. Overall, our results suggest that impaired phoneme representations in dyslexia may be explained, at least partially, by articulatory deficits affecting access to them.

One-to-One or One Too Many? Linking Sound-to-Letter Mappings to Speech Sound Perception and Production in Early Readers

PURPOSE

Effects related to literacy acquisition have been observed at different levels of speech processing. This study investigated the link between orthographic knowledge and children's perception and production of specific speech sounds.

METHOD

Sixty Spanish-speaking second graders, differing in their phonological decoding skills, completed a speech perception and a production task. In the perception task, a behavioral adaptation of the oddball paradigm was used. Children had to detect orthographically consistent /t/, which has a unique orthographic representation (〈t〉), and inconsistent /k/, which maps onto three different graphemes (〈c〉, 〈qu〉, and 〈k〉), both appearing infrequently within a repetitive auditory sequence. In the production task, children produced these same sounds in meaningless syllables.

RESULTS

Perception results show that all children were faster at detecting consistent than inconsistent sounds regardless of their decoding skills. In the production task, however, the same facilitation for consistent sounds was linked to better decoding skills.

CONCLUSIONS

These findings demonstrate differences in speech sound processing related to literacy acquisition. Literacy acquisition may therefore affect already-formed speech sound representations. Crucially, the strength of this link in production is modulated by individual decoding skills.

Developmental Changes in Coarticulation Degree Relate to Differences in Articulatory Patterns: An Empirically Grounded Modeling Approach

PURPOSE

Coarticulatory effects in speech vary across development, but the sources of this variation remain unclear. This study investigated whether developmental differences in intrasyllabic coarticulation degree could be explained by differences in children's articulatory patterns compared to adults.

METHOD

To address this question, we first compared the tongue configurations of 3- to 7-year-old German children to those of adults. The observed developmental differences were then examined through simulations with Task Dynamics Application, a Task Dynamics simulation system, to establish which articulatory modifications could best reproduce the empirical results. To generate syllables simulating the lack of tongue gesture differentiation, we tested three simulation scenarios.

RESULTS

We found that younger speakers use less differentiated articulatory patterns to achieve alveolar constrictions than adults. The simulations corresponding to undifferentiated control of tongue tip and tongue body resulted in (a) tongue shapes similar to those observed in natural speech and (b) higher degrees of intrasyllabic coarticulation in children when compared to adults.

CONCLUSIONS

Results provide evidence that differences in articulatory patterns contribute to developmental differences in coarticulation degree. This study further shows that empirically informed modeling can advance our understanding of changes in coarticulatory patterns across age.

LANGUAGE EXPOSURE PREDICTS CHILDREN'S PHONETIC PATTERNING: EVIDENCE FROM LANGUAGE SHIFT

Although understanding the role of the environment is central to language acquisition theory, rarely has this been studied for children's phonetic development, and receptive and expressive language experiences in the environment are not distinguished. This last distinction may be crucial for child speech production in particular, because production requires coordination of low-level speech-motor planning with high-level linguistic knowledge. In this study, the role of the environment is evaluated in a novel way-by studying phonetic development in a bilingual community undergoing rapid language shift. This sociolinguistic context provides a naturalistic gradient of the amount of children's exposure to two languages and the ratio of expressive to receptive experiences. A large-scale child language corpus encompassing over 500 hours of naturalistic South Bolivian Quechua and Spanish speech was efficiently annotated for children's and their caregivers' bilingual language use. These estimates were correlated with children's patterns in a series of speech production tasks. The role of the environment varied by outcome: children's expressive language experience best predicted their performance on a coarticulation-morphology measure, while their receptive experience predicted performance on a lower-level measure of vowel variability. Overall these bilingual exposure effects suggest a pathway for children's role in language change whereby language shift can result in different learning outcomes within a single speech community. Appropriate ways to model language exposure in development are discussed.

A temporal-based therapy for children with inconsistent phonological disorder: A case-series

Deficits in temporal auditory processing, and in particular higher gap detection thresholds have been reported in children with inconsistent phonological disorder (IPD). Here we hypothesized that providing these children with extra time for phoneme identification may in turn enhance their phonological planning abilities for production, and accordingly improve not only consistency but also accuracy of their speech. We designed and tested a new temporal-based therapy, inspired by Core Vocabulary Therapy and called it T-CVT, where we digitally lengthened formant transitions between phonemes of words used for therapy. This allowed to target both temporal auditory processing and word phonological planning. Four preschool Persian native children with IPD received T-CVT for eight weeks. We measured changes in speech consistency (% inconsistency) and accuracy (percentage of consonants correct PCC) to assess the effects of the intervention. Therapy significantly improved both consistency and accuracy of word production in the four children: % inconsistency decreased from 59% on average before therapy to 2% post-T-CVT, and PCC increased from 61% to 92% on average. Consistency and accuracy were furthermore maintained or even still improved at three-month follow-up (2% inconsistency and 99% PCC). Results in a nonword repetition task showed the generalization of these effects to non-treated material: % inconsistency for nonwords decreased from 67% to 10% post-therapy, and PCC increased from 63% to 90%. These preliminary findings support the efficacy of the T-CVT intervention for children with IPD who show temporal auditory processing deficits as reflected by higher gap detection thresholds.

Auditory feedback experience in the development of phonetic production: Evidence from preschoolers with cochlear implants and their normal-hearing peers

Previous work has found that preschoolers with greater phonological awareness and larger lexicons, who speak more throughout the day, exhibit less intra-syllabic coarticulation in controlled speech production tasks. These findings suggest that both linguistic experience and speech-motor control are important predictors of spoken phonetic development. Still, it remains unclear how preschoolers' speech practice when they talk drives the development of coarticulation because children who talk more are likely to have both increased fine motor control and increased auditory feedback experience. Here, the potential effect of auditory feedback is studied by examining a population-children with cochlear implants (CIs)-which is naturally differing in auditory experience. The results show that (1) developmentally appropriate coarticulation improves with an increased hearing age but not chronological age; (2) children with CIs pattern coarticulatorily closer to their younger, hearing age-matched peers than chronological age-matched peers; and (3) the effects of speech practice on coarticulation, measured using naturalistic, at-home recordings of the children's speech production, only appear in the children with CIs after several years of hearing experience. Together, these results indicate a strong role of auditory feedback experience on coarticulation and suggest that parent-child communicative exchanges could stimulate children's own vocal output, which drives speech development.

The coarticulation-duration relationship in early Quechua speech

Evidence from acoustic and articulatory phonetics suggests that children coarticulate more than adults, but previous work has focused on the instantiation of coarticulation with phonology in a typologically homogeneous sample. The interplay of coarticulation with children's speaking rate has also been ignored. How do coarticulation and speaking rate (duration) interact over the course of development, and does the interaction manifest differently across distinct morphological environments? To answer this, the current study measured the speech patterns of bilingual Quechua-Spanish children (5-10 years) and adults. Coarticulation and duration were measured in two word environments, within morphemes and across morpheme boundaries. Unsurprisingly, adults consistently coarticulated more in shorter duration sequences, in both morphological environments. The children's coarticulation-duration patterns, however, varied by morphological environment. Additionally, the children's speech patterns, but not the adults', were sensitive to prosodic length: children produced increasingly shorter phones in words with more syllables. It is suggested that the differences between adults and children are attributable to adults' faster speaking rate and increased dominance in Quechua.

Coherence Between Brain Activation and Speech Envelope at Word and Sentence Levels Showed Age-Related Differences in Low Frequency Bands

Speech perception is dynamic and shows changes across development. In parallel, functional differences in brain development over time have been well documented and these differences may interact with changes in speech perception during infancy and childhood. Further, there is evidence that the two hemispheres contribute unequally to speech segmentation at the sentence and phonemic levels. To disentangle those contributions, we studied the cortical tracking of various sized units of speech that are crucial for spoken language processing in children (4.7-9.3 years old, N = 34) and adults (N = 19). We measured participants' magnetoencephalogram (MEG) responses to syllables, words, and sentences, calculated the coherence between the speech signal and MEG responses at the level of words and sentences, and further examined auditory evoked responses to syllables. Age-related differences were found for coherence values at the delta and theta frequency bands. Both frequency bands showed an effect of stimulus type, although this was attributed to the length of the stimulus and not the linguistic unit size. There was no difference between hemispheres at the source level either in coherence values for word or sentence processing or in evoked response to syllables. Results highlight the importance of the lower frequencies for speech tracking in the brain across different lexical units. Further, stimulus length affects the speech-brain associations suggesting methodological approaches should be selected carefully when studying speech envelope processing at the neural level. Speech tracking in the brain seems decoupled from more general maturation of the auditory cortex.

Practice and experience predict coarticulation in child speech

Much research in child speech development suggests that young children coarticulate more than adults. There are multiple, not mutually-exclusive, explanations for this pattern. For example, children may coarticulate more because they are limited by immature motor control. Or they may coarticulate more if they initially represent phonological segments in larger, more holistic units such as syllables or feet. We tested the importance of several different explanations for coarticulation in child speech by evaluating how four-year-olds' language experience, speech practice, and speech planning predicted their coarticulation between adjacent segments in real words and paired nonwords. Children with larger vocabularies coarticulated less, especially in real words, though there were no reliable coarticulatory differences between real words and nonwords after controlling for word duration. Children who vocalized more throughout a daylong audio recording also coarticulated less. Quantity of child vocalizations was more predictive of the degree of children's coarticulation than a measure of receptive language experience, adult word count. Overall, these results suggest strong roles for children's phonological representations and speech practice, as well as their immature fine motor control, for coarticulatory development.

A lexical advantage in four-year-old children's word repetition

This study examined a potential lexicality advantage in young children's early speech production: do children produce sound sequences less accurately in nonwords than real words? Children aged 3;3-4;4 completed two tasks: a real word repetition task and a corresponding nonword repetition task. Each of the 23 real words had a paired consonant-vowel sequence in the nonword in word-initial position (e.g., 'su' in ['sutkes] 'suitcase' and ['sudrɑs]). The word-initial consonant-vowel sequences were kept constant between the paired words. Previous work on this topic compared different sequences of paired sounds, making it hard to determine if those results were due to a lexical or phonetic effect. Our results show that children reliably produced consonant-vowel sequences in real words more accurately than nonwords. The effect was most pronounced in children with smaller receptive vocabularies. Together, these results reinforce theories arguing for interactions between vocabulary size and phonology in language development.