Parents tune their vowels to the emergence of children's words.

The aim of this study was to investigate the acoustic vowel space area in infant directed speech (IDS). The research question is whether the vowel space is expanded or remains constant in IDS. A corpus of spontaneous interactions of 9 dyads followed monthly from the age of 6 to 24 months was analyzed. The occurrences in the parents' speech of each word that the children eventually acquired were extracted. The surface of the vowel triangle and the convex hull of all vowels were computed. The main result is that the development of the vowel space in IDS follows an inverted U-shaped curve: the vowel space starts relatively small, gradually increases as the child's first word use approaches, and decreases again afterwards. These findings show that parents adapt their articulation to the evolving linguistic abilities of their child, and this adaptation can be detected at the level of individual lexical items.

Spontaneous speech intelligibility: early cochlear implanted children versus their normally hearing peers at seven years of age.

Speaking intelligibly is an important achievement in children's language development. How far do congenitally severe-to-profound hearing-impaired children who received a cochlear implant (CI) in the first two years of their life advance on the path to intelligibility in comparison to children with typical hearing (NH)? Spontaneous speech samples of children with CI and children with NH were orthographically transcribed by naïve transcribers. The entropy of the transcriptions was computed to analyze their degree of uniformity. The same samples were also rated on a continuous rating scale by another group of adult listeners. The transcriptions of the NH children's speech were more uniform, i.e., had significantly lower entropy, than those of the CI children, suggesting that the latter group displayed lower intelligibility. This was confirmed by the ratings on the continuous scale. Despite the relatively restricted age ranges, older children reached better intelligibility scores in both groups.

Intraword Variability in Children With Auditory Brainstem Implants: A Longitudinal Comparison With Children With Cochlear Implants.

PURPOSE: Intraword variability designates the phenomenon that a particular target word is produced variably by a child at one point in the child's development. In this study, the amount of intraword variability is studied longitudinally in children with auditory brainstem implants (ABIs). Auditory brainstem implantation is a relative recent technique in pediatric hearing restoration. Therefore, little is known about the phonological development of these children's speech. METHOD: The intraword variability is investigated in three children with ABI, in comparison to children with cochlear implants, matched on lexical development. Intraword variability is measured using relative entropy in order to take into account the frequency distribution in children's productions. RESULT: Results showed considerable variation between the three children with ABI. Still, all children had higher levels of intraword variability in their spontaneous speech productions as compared to children with cochlear implants. CONCLUSION: It seems that children with ABI are lagging behind their phonological development in reference to children with cochlear implants.

Speech intelligibility of children with an auditory brainstem implant: a triple-case study.

Auditory brainstem implantation (ABI) is a relative recent development in paediatric hearing restoration. Consequently, young-implanted children's productive language has not received much attention. This study investigated speech intelligibility of children with ABI (N = 3) in comparison to children with cochlear implants (CI) and children with typical hearing (TH). Spontaneous speech samples were recorded from children representing the three groups matched on cumulative vocabulary level. Untrained listeners (N = 101) rated the intelligibility of one-word utterances on a continuous scale and transcribed each utterance. The rating task yielded a numerical score between 0 and 100, and similarities and differences between the listeners' transcriptions were captured by a relative entropy score. The speech intelligibility of children with CI and children with TH was similar. Speech intelligibility of children with ABI was well below that of the children with CI and TH. But whereas one child with ABI's intelligibility approached that of the control groups with increasing lexicon size, the intelligibility of the two other children with ABI did not develop in a similar direction. Overall, speech intelligibility was only moderate in the three groups of children, with quite low ratings and considerable differences in the listeners' transcriptions, resulting in high relative entropy scores.

Tailoring the Input to Children's Needs: The Use of Fine Lexical Tuning in Speech Directed to Normally Hearing Children and Children With Cochlear Implants.

Purpose: The aim of the present study was to explore fine lexical tuning in Dutch infant-directed speech (IDS) addressed to congenitally deaf infants who received a cochlear implant (CI) early in life (<2 years of age) in comparison with children with normal hearing (NH). The longitudinal pattern of parents' utterance length in the initial stages of the child's lexical development was examined. Parents' utterances containing the words the children eventually acquired in the earliest developmental stages were selected and their MLU (Mean Length of Utterance) was measured. Method: Transcriptions of monthly recordings of spontaneous interactions of 10 CI children and 30 NH children with their parents were analyzed. The children with CI were followed from the moment their device was switched on, and the NH children from the age of 6 months onwards. A total of 57,846 utterances of parents of CI children and 149,468 utterances of parents of NH children were analyzed. Results: IDS addressed to children with NH and children with CI exhibits fine lexical tuning: parents adjust the MLU of the utterances that contain the words that children are on the verge of producing themselves. More specifically, the parents' mean length of those utterances decreased in relation to the point when the children began using the item. Consequently, the number of occurrences in isolation of the lexical item increased. The speech addressed to all the children exhibited this phenomenon, but it was significantly more strongly present in speech addressed to the children with CI. Conclusions: The speech addressed to children with NH and CI is characterized by fine lexical tuning and a high incidence of single-word utterances in the period leading up to the children's first use of words in speech production. Notwithstanding striking commonalities, IDS addressed to children with a hearing impairment is markedly different, which suggests that parents take this specific character of the children into account.

Consonant and vowel production in the spontaneous speech productions of children with auditory brainstem implants.

Auditory brainstem implantation provides hearing sensations in children and adults with anomalies of the auditory nerves. In children, perceptual benefits have been established, and research already demonstrated (limited) effects on children's speech production. The current study extends the literature by scrutinizing the phonological development of three children with ABI. Spontaneous speech samples were used to establish their phonemic inventories of vowels, word-initial consonants and word-final consonants, both independently of the target phoneme and relative to the target phoneme. The three children produced all vowels with longer device use and larger vocabulary size. Word-initial and word-final consonants appeared in the three children's spontaneous productions. However, the segmental accuracy was only moderate in the children's productions.

Word characteristics and speech production accuracy in children with auditory brainstem implants: a longitudinal triple case report.

Auditory brainstem implants (ABI) in children in the first years of life is a recent innovation. Analyses of their speech and language development on the basis of spontaneous language samples are still largely lacking. The aim was to investigate the phonological complexity of the words children with ABI use in their spontaneous speech, and to compare their accuracy with that of children with cochlear implants (CI) and children with normal hearing (NH). Longitudinal recordings of spontaneous speech were collected of three children with ABI. Children with ABI target mainly words of low phonological complexity in their spontaneous speech, just as children with NH and children with CI do. The complexity of the words they attempt increases over time, but this development is less outspoken in comparison to children with CI and NH at the same hearing ages. The accuracy of the ABI children's word productions is situated in the lower ranges of the 95% confidence intervals of the NH and the CI groups, and - depending on the specific measure - even fall below the 95% border. The ABI intervention appears to be beneficial in the three cases studied, although their development is slow compared to children with CI and NH.

Fine lexical tuning in infant directed speech to typically developing children.

Do parents fine-tune the MLU of utterances with a particular word as the word is on the verge of appearing in the child's production? We analyzed a corpus of spontaneous interactions of 30 dyads. The children were in the initial stages of their lexical development, and the parents' utterances containing the words the children eventually acquired were selected. The main finding is that the MLU of the parental utterances containing the target words gradually decreased up to the point of the children's first production of those words. This suggests that parents fine-tune their utterances to support the children's linguistic development.

Native and non-native listeners' judgements on the overall speech quality of hearing-impaired children.

This study focuses on the influence of listeners' native language on their judgement of the overall speech quality of normally hearing (NH) and hearing-impaired (HI) children. Studies have shown that listeners' native language influences their judgements on linguistic aspects of a foreign language. Since judging speech quality does in principle not require any knowledge of the language, the question arose if the native language influences listeners' judgements. For this purpose, the overall speech quality of seven-year-old Dutch speaking children (n = 21) with an acoustic hearing aid (HA), a cochlear implant (CI) and normal hearing (NH) was judged by four listener groups (native speakers of Italian, German, French and Dutch). Listeners completed a comparative judgement task in which stimuli were presented in pairs. For each pair, they selected the better sounding stimulus. This procedure ultimately led to a ranking of the stimuli according to their speech quality. The ranking showed that NH children had a significantly higher speech quality than HI children. Interestingly, there was no significant effect of language background. Both native and non-native listeners perceived a significant difference in speech quality. Also, within the group of HI children, all listener groups preferred the speech of CI children when comparing them to HA children. These results indicated that the differences were purely speech related since the non-native listeners had no linguistic knowledge of Dutch. Considering that all listeners perceived a similar qualitative difference, we conclude that there was no transfer of native language in this type of judgement.

Is the spontaneous speech of 7-year-old cochlear implanted children as intelligible as that of their normally hearing peers?

OBJECTIVES: Studies on speech intelligibility usually focus on either individual words, sentences or longer sequences of speech. Since these different kinds of speech samples can be judged using different methodologies, a difference in the reported intelligibility scores can either be due to the difference in the type of sample or methodology. The present study compares the speech intelligibility of seven-year-old children with a cochlear implant (CI) with that of their normally hearing (NH) peers. The first aim is to compare the intelligibility of short sentences and longer sequences of speech using the same methodology. Secondly, it has been suggested that i.a. advances in CI technology and changes in candidacy criteria may have had a positive influence on the intelligibility of children with CI. In order to assess this issue, the intelligibility of seven-year-olds implanted ten years apart will be compared. METHOD: The speech of two cohorts of early implanted children with CI (n = 16) and NH peers (n = 16), matched on several criteria but implanted in different years, was collected. More specifically, short and longer samples were selected from recordings of a wordless picture book retelling. Both types of samples were judged on a visual analogue scale by 105 inexperienced listeners. RESULTS: The results showed that the intelligibility of children with CI was lower than that of their NH peers. Moreover, longer samples were significantly more intelligible than short samples for both groups. No significant effect was found between the two cohorts of children with CI. However, the intelligibility of three out of four children with CI was found to be on a par with that of their NH peers, indicating a large amount of variability between subjects. CONCLUSION: Listeners ascribed higher intelligibility to longer samples than to short samples, despite the fact that both types were extracted from the same recordings and listeners followed the same judgement procedure. The amount of context thus facilitated speech decoding. No effect of the calendar year of implantation was found, suggesting that e.g., the evolution in CI technology did not have a significant impact on CI users' intelligibility after six years of device use.

Input-output relations in Hebrew verb acquisition at the morpho-lexical interface.

This study examined early Hebrew verb acquisition, highlighting CDS-CS relations across inflectional and derivational verb learning. It was carried out on a corpus of longitudinal dense dyadic interactions of two Hebrew-speaking toddlers aged 1;8-2;2 and their parents. Findings revealed correlated patterns within and between CDS and CS corpora in terms of verbs, structural root categories, and their components (roots, binyan conjugations, and derivational verb families), and clear relations between lexical-derivational development and inflectional growth in input-output relations, measured by MSP. It also showed that both corpora had few, yet highly semantically coherent, derivational families. Lexical learning in Hebrew was shown to be morphologically oriented, with both inflectional and derivational learning supporting and being supported by the development of the verb lexicon. These findings support findings in the general literature regarding the close relationship between parental input and child speech, and the affinity between lexical and grammatical growth.

Rating the overall speech quality of hearing-impaired children by means of comparative judgements.

OBJECTIVE: Acoustic measurements have shown that the speech of hearing-impaired (HI) children deviates from the speech of normally hearing (NH) peers. The aim of the present study is to examine whether listeners with varying degrees of experience with (HI) children's speech perceive a difference in the overall speech quality of seven-year-old NH children and their HI peers who received a device before the age of two. METHOD: Short speech samples of seven children with NH, seven children with an acoustic hearing aid (HA) and seven children with a cochlear implant (CI) were judged by three groups of listeners (audiologists, primary school teachers and inexperienced listeners) in a comparative judgement task. In this task, listeners compared stimuli in pairs and decided which stimulus sounded better, leading to a ranking of the stimuli according to their overall speech quality. RESULTS: The ranking showed that the overall speech quality differed considerably for HI and NH children. The latter group had a significantly higher overall speech quality than HI children. In the group of HI children, children with CI were ranked higher than children with HA. Moreover, length of device use was found to have a significant effect in the group of children with CI: longer device experience led to better ratings. This effect was significantly less strong in HA children. No significant differences were found between the three groups of listeners. CONCLUSION: Listeners agree that the speech of NH children sounds better than the speech of HI children. This result indicates that even after almost seven years of device use, the speech of HI children still differs from the speech of NH children. The overall speech quality of CI children was better than that of HA children, and this effect increased with longer device use. No effect of listeners' experience with (NH and/or HI) children's speech was established.

Expressive Vocabulary Growth After Pediatric Auditory Brainstem Implantation in Two Cases' Spontaneous Productions: A Comparison With Children With Cochlear Implants and Typical Hearing.

Auditory brainstem implants (ABI) are recently being used to restore hearing of children with a congenital hearing loss, due to for instance the absence of auditory nerves. Thus far, the literature has focused on perceptual outcomes. The present study is among the first ones to investigate the spoken language development after implantation. The lexical development of children with ABI is examined longitudinally in comparison to children with typical hearing and children with cochlear implants. Results show that children with ABI still have smaller spoken vocabularies as compared to (hearing) age-matched children with cochlear implants and children with typical hearing. Implications will be discussed.

Listeners' perception of lexical stress in the first words of infants with cochlear implants and normally hearing infants.

Normally hearing (NH) infants are able to produce lexical stress in their first words, but congenitally hearing-impaired children with cochlear implants (CI) may find this more challenging, given the limited transmission of spectro-temporal information by the implant. Acoustic research has shown that the acoustic cues to stress in the first words of Dutch-acquiring CI infants are less pronounced (Pettinato, De Clerck, Verhoeven, & Gillis, 2017). The present study investigates how listeners perceive lexical stress in the first words of CI and NH infants. Two research questions are addressed: (1) How successful are CI and NH children in implementing the prosodic cues to prominence? (2) Is the degree of stress in CI and NH words perceived to be similar? The stimuli used in this study are disyllabic words (n = 1089) produced by 9 infants with CI and 9 NH infants acquiring Dutch. The words were presented to adult listeners in a listening experiment, in which they assessed the stress pattern on a continuous visual analogue scale (VAS) which expresses to what extent syllables are perceived as stressed. The results show that listeners perceive typical word stress production in the first words of infants with CI. The words of CI and NH infants were rated in agreement with the target stress pattern as often, and trochaic words were rated more frequently as such than iambic words. Listeners more frequently perceive unstressed syllables in the first words of infants with CI. However, for the words that are perceived to be clearly stressed, the degree of word stress is comparable in the two groups, and both infant groups are perceived to produce more contrast between stressed and unstressed syllables in trochees than in iambs. It is concluded that that acoustic differences between CI and NH infants' stress production are not necessarily perceptually salient.

Simulating speech processing with cochlear implants: How does channel interaction affect learning in neural networks?

We introduce a novel machine learning approach for investigating speech processing with cochlear implants (CIs)-prostheses used to replace a damaged inner ear. Concretely, we use a simple perceptron and a deep convolutional network to classify speech spectrograms that are modified to approximate CI-delivered speech. Implant-delivered signals suffer from reduced spectral resolution, chiefly due to a small number of frequency channels and a phenomenon called channel interaction. The latter involves the spread of information from neighboring channels to similar populations of neurons and can be modeled by linearly combining adjacent channels. We find that early during training, this input modification degrades performance if the networks are first pre-trained on high-resolution speech-with a larger number of channels, and without added channel interaction. This suggests that the spectral degradation caused by channel interaction alters the signal to conflict with perceptual expectations acquired from high-resolution speech. We thus predict that a reduction of channel interaction will accelerate learning in CI users who are implanted after having adapted to high-resolution speech during normal hearing. (The code for replicating our experiments is available online: https://github.com/clips/SimulatingCochlearImplants).

Children Probably Store Short Rather Than Frequent or Predictable Chunks: Quantitative Evidence From a Corpus Study.

One of the tasks faced by young children is the segmentation of a continuous stream of speech into discrete linguistic units. Early in development, syllables emerge as perceptual primitives, and the wholesale storage of syllable chunks is one possible strategy for bootstrapping the segmentation process. Here, we investigate what types of chunks children store. Our method involves selecting syllabified utterances from corpora of child-directed speech, which we vary according to (a) their length in syllables, (b) the mutual predictability of their syllables, and (c) their frequency. We then use the number of utterances within which words are contained to predict the time course of word learning, arguing that utterances which perform well at this task are also more likely to be stored, by young children, as undersegmented chunks. Our results show that short utterances are best-suited for predicting when children acquire the words contained within them, although the effect is rather small. Beyond this, we also find that short utterances are the most likely to correspond to words. Together, the two findings suggest that children may not store many complete utterances as undersegmented chunks, with most of the units that children store as hypothesized words corresponding to actual words. However, dovetailing with an item-based account of language-acquisition, when children do store undersegmented chunks, these are likely to be short sequences-not frequent or internally predictable multi-word chunks. We end by discussing implications for work on formulaic multi-word sequences.

Auditory brainstem implantation in children with hearing loss: Effect on speech production.

Auditory brainstem implantation (ABI) is a recent technique in children's hearing restoration. Up till now the focus in the literature has mainly been the perceptual outcomes after implantation, whereas the effect of ABI on spoken language is still an almost unexplored area of research. This study presents a one-year follow-up of the volubility of two children with ABI. The volubility of signed and oral productions is investigated and oral productions are examined in more detail. Results show clear developmental trends in both children, indicating a beneficial effect of ABI on spoken language development.

Can listeners hear the difference between children with normal hearing and children with a hearing impairment?

Acoustic measurements have shown that the speech of hearing-impaired (HI) children differs from that of normally hearing (NH) children, even after several years of device use. This study focuses on the perception of HI speech in comparison to NH children's speech. The purpose of this study was to investigate whether adult listeners can identify the speech of NH and HI children. Moreover, it is studied whether listeners' experience and the children's length of device use play a role in that assessment. For this study, short utterances of 7 children with a cochlear implant (CI), 7 children with an acoustic hearing aid (HA) and 7 children with NH were presented to 90 listeners who were required to specify the hearing status of each speech sample. The judges had different degrees of familiarity with hearing disorders: there were 30 audiologists, 30 primary schoolteachers and 30 inexperienced listeners. The results show that the speech of children with NH and HI can reliably be identified. However, listeners do not manage to distinguish between children with CI and HA. Children with CI are increasingly identified as NH with increasing length of device use. For children with HA, there is no similar change with longer device use. Also, experienced listeners seem to display a more lenient attitude towards atypical speech, whereas inexperienced listeners are stricter and generally consider more utterances to be produced by children with HI.

Lexical category acquisition is facilitated by uncertainty in distributional co-occurrences.

This paper analyzes distributional properties that facilitate the categorization of words into lexical categories. First, word-context co-occurrence counts were collected using corpora of transcribed English child-directed speech. Then, an unsupervised k-nearest neighbor algorithm was used to categorize words into lexical categories. The categorization outcome was regressed over three main distributional predictors computed for each word, including frequency, contextual diversity, and average conditional probability given all the co-occurring contexts. Results show that both contextual diversity and frequency have a positive effect while the average conditional probability has a negative effect. This indicates that words are easier to categorize in the face of uncertainty: categorization works best for words which are frequent, diverse, and hard to predict given the co-occurring contexts. This shows how, in order for the learner to see an opportunity to form a category, there needs to be a certain degree of uncertainty in the co-occurrence pattern.

Intraword Variability in Children With Cochlear Implants: The Long-Term Development up to 5 Years of Age and a Comparison With Children With Normal Hearing.

Purpose: This study evaluates intraword or token-to-token variability in the spontaneous speech of Dutch-speaking children with cochlear implants (CIs) longitudinally up to 5 years of age in comparison with intraword variability in age-matched peers with normal hearing (NH). Method: Spontaneous speech samples of 9 children with CI were collected longitudinally up to age 5. The data of the NH control group consisted of cross-sectional recordings. Children's word productions were categorized into 4 response types of the variability score (consistent correct, consistent incorrect, variable with hits, variable with no hits), and the proportion of whole-word variation (PWV) was calculated. Results: PWV was high in both groups of children but decreased with age. All response types of the variability score appeared in both groups. Children with CI were significantly more variable than their peers with NH up to age 4, but this difference has disappeared by age 5. Longer words had a higher PWV and were more often consistent incorrect and variable. Conclusions: Intraword variability was characteristic of children with CI's spontaneous speech productions as it was in children with NH, and a similar factor (word length) affected variability in production. Group comparisons showed higher rates of intraword variability in children with CI, but they seemed to catch up with their peers with NH by age 5.