Investigation of coarticulation in typically developing children and adults

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.

Coarticulatory patterns in developing speech have long been considered to provide a window into speech maturation. Previous research showing that children demonstrate greater degrees of intra-syllabic lingual coarticulation compared to adults has attributed these findings to developmental differences in independent control of speech articulators. This study investigated the relationship between developmental differences in intra-syllabic coarticulation degree and developmental differences in articulatory strategies.

This work tests the hypothesis that age-related differences in coarticulatory patterns are related to developmental changes in articulatory strategies using ultrasound data analysis and task dynamical computational simulation.

Understanding the development of spoken language in young children has become increasingly important for advancing basic theories of language acquisition and for clinical practice. However, such a goal requires refined measurements of speech articulation (e.g., from the tongue), which are difficult to obtain from young children. In recent years though, technological advances have allowed developmental researchers to make significant steps in that direction. For instance, movements of the tongue, an articulator that is essential for spoken language, can now be tracked and recorded in children with ultrasound imaging. This technique has opened novel research avenues in (a)typical language acquisition, enabling researchers to reliably capture what has long remained invisible in the speech of young children. Within this context, we have designed an experimental platform for the recording and the processing of kinematic data: SOLLAR (Sonographic and Optical Linguo-Labial Articulatory Recording system). The method has been tailored for children, but it is suitable for adults. In the present article, we introduce the recording environment developed to record over 100 children and 30 adults within SOLLAR. We then describe SOLLAR’s data processing framework, providing examples of data visualization and a summary of strengths and limitations.

This study is the first to use kinematic data to assess lingual carryover coarticulation in children. We investigated whether the developmental decrease previously attested in anticipatory coarticulation, as well as the relation between coarticulatory degree and the consonantal context, also characterize carryover coarticulation. Sixty-two children and 13 adults, all native speakers of German, were recruited according to five age cohorts: three-year-olds, four-year-olds, five-year-olds, seven-year-olds, and adults. Tongue movements during the production of ə.CV.Cə utterances (C = /b, d, g/, V = /i, y, e, a, o, u/) were recorded with ultrasound. We measured vowel-induced horizontal displacement of the tongue dorsum within the last syllable and compared the resulting coarticulatory patterns between age cohorts and consonantal contexts. Results indicate that the degree of vocalic carryover coarticulation decreases with age. Vocalic prominence within an utterance as well as its change across childhood depended on the postvocalic consonant’s articulatory demands for the tongue dorsum (i.e., its coarticulatory resistance): Low resistant /b/ and /g/ allowed for more vocalic perseveration and a continuous decrease, while the highly resistant /d/ displayed lower coarticulation degrees and discontinuous effects. These findings parallel those in anticipation suggesting a similar organization of anticipatory and carryover coarticulation. Implications for theories of speech production are discussed.

The development of phonological awareness, the knowledge of the structural combinatoriality of a language, has been widely investigated in relation to reading (dis)ability across languages. However, the extent to which knowledge of phonemic units may interact with spoken language organization in (transparent) alphabetical languages has hardly been investigated. The present study examined whether phonemic awareness correlates with coarticulation degree, commonly used as a metric for estimating the size of children’s production units. A speech production task was designed to test for developmental differences in intra-syllabic coarticulation degree in 41 German children from 4 to 7 years of age. The technique of ultrasound imaging allowed for comparing the articulatory foundations of children’s coarticulatory patterns. Four behavioral tasks assessing various levels of phonological awareness from large to small units and expressive vocabulary were also administered. Generalized additive modeling revealed strong interactions between children’s vocabulary and phonological awareness with coarticulatory patterns. Greater knowledge of sub-lexical units was associated with lower intra-syllabic coarticulation degree and greater differentiation of articulatory gestures for individual segments. This interaction was mostly nonlinear: an increase in children’s phonological proficiency was not systematically associated with an equivalent change in coarticulation degree. Similar findings were drawn between vocabulary and coarticulatory patterns. Overall, results suggest that the process of developing spoken language fluency involves dynamical interactions between cognitive and speech motor domains. Arguments for an integrated-interactive approach to skill development are discussed.

This study is the first to use kinematic data to assess lingual carryover coarticulation in children. We investigated whether the developmental decrease previously attested in anticipatory coarticulation, as well as the relation between coarticulatory degree and the consonantal context, also characterize carryover coarticulation. Sixty-two children and 13 adults, all native speakers of German, were recruited according to five age cohorts: three-year-olds, four-year-olds, five-year-olds, seven-year-olds, and adults. Tongue movements during the production of ə.CV.Cə utterances (C = /b, d, g/, V = /i, y, e, a, o, u/) were recorded with ultrasound. We measured vowel-induced horizontal displacement of the tongue dorsum within the last syllable and compared the resulting coarticulatory patterns between age cohorts and consonantal contexts. Results indicate that the degree of vocalic carryover coarticulation decreases with age. Vocalic prominence within an utterance as well as its change across childhood depended on the postvocalic consonant’s articulatory demands for the tongue dorsum (i.e., its coarticulatory resistance): Low resistant /b/ and /g/ allowed for more vocalic perseveration and a continuous decrease, while the highly resistant /d/ displayed lower coarticulation degrees and discontinuous effects. These findings parallel those in anticipation suggesting a similar organization of anticipatory and carryover coarticulation. Implications for theories of speech production are discussed.

The development of phonological awareness, the knowledge of the structural combinatoriality of a language, has been widely investigated in relation to reading (dis)ability across languages. However, the extent to which knowledge of phonemic units may interact with spoken language organization in (transparent) alphabetical languages, has hardly been investigated. The present study examined whether a developmental gain in phonemic awareness correlates with a decrease in coarticulation degree, commonly used as a metric for estimating the size of children´s production units. A speech production task was designed to test for developmental differences in intra-syllabic coarticulation degree in 66 German children from 4 to 7 years of age. The technique of ultrasound imaging allowed for comparing the articulatory foundations of children´s coarticulatory patterns. Four behavioral tasks assessing various levels of phonological awareness from large to small units and expressive vocabulary were also administered. Generalized additive modelling revealed strong interactions between children´s vocabulary, phonological awareness and coarticulatory patterns. Greater knowledge of sub-lexical units correlated with lower intra-syllabic coarticulation degree and greater differentiation of articulatory gestures for consecutive segments. This interaction was mostly nonlinear: an increase in children’s phonological proficiency was not systematically associated with an equivalent change in coarticulation degree. Similar findings were drawn between vocabulary and coarticulatory patterns. Overall, results suggest that the process of developing spoken language fluency involves dynamical interactions between vocabulary, phonological awareness and speech motor control. Arguments for an integrated-interactive approach to skill development are discussed.

This study examines the temporal organization of vocalic anticipation in German children from 3 to 7 years of age and adults. The main objective was to test for non-linear processes in vocalic anticipation, which may result from the interaction between lingual gestural goals for individual vowels, and those for their neighbors over time. The technique of ultrasound imaging was employed to record tongue movement at five time points throughout short utterances of the form V1#CV2. Vocalic anticipation was examined with Generalized Additive Modeling, an analytical approach allowing for the estimation of both linear and non-linear influences on anticipatory processes. Both adults and children exhibit non-linear patterns of vocalic anticipation over time with the degree and extent of vocalic anticipation varying as a function of the individual consonants and vowels assembled. However, noticeable developmental discrepancies were found with vocalic anticipation being present earlier in children´s utterances at 3-4-5 years of age in comparison to adults and to some extent 7-year-old children. A narrowing of speech production organization from large chunks in kindergarten to more segmentally differentiated and contextually-specified organizations from kindergarten to primary school to adulthood, although variation in the temporal overlap of lingual gestures for consecutive segments is already present in the youngest cohorts. In adults, non-linear anticipatory patterns over time suggest a strong differentiation between the gestural goals for consecutive segments. In children, this differentiation is not yet mature: vowels show greater prominence over time and seem activated more in-phase with those of previous segments relative to adults.

Learning to speak a language is related to the emergence of sensorimotor “maps” in which vowels and consonants are associated with articulatory-acoustic vocal tract configurations. One main challenge for young children is to develop these associations while integrating anatomical changes, as well as motor, perceptual, and cognitive abilities (Green, Moore, & Reilly, 2002; Kuhl & Meltzoff, 1982; Vorperian et al., 2005). There is empirical evidence that the physical growth in the vocal tract is not complete until adolescence (Kent, 2004). Hence, from birth to adulthood, the production of vowels and consonants is likely to reflect continuous articulatory and acoustic adjustments, as the production system matures. Determining the exact role of each component (anatomical, motor, perceptual, and cognitive) for producing intelligible speech is a complex task, especially from an ontogenetic perspective. The objective of this paper is to study the articulatory strategies used by children to produce speech targets. Those targets can be considered as phonological goals, implemented by phonetic articulatory gestures. Considering the facts that (i) 4-year-old children can produce intelligible phonemes, (ii) their motor control capacities are still immature, and (iii) their vocal tract anatomy greatly differs from that of adults, it is hypothesized that they use different phonetic strategies compared to adults to implement phonological targets. This report is part of a larger research program we have developed with our collaborators for the last decade (Ménard et al., 2000; 2004). For the first time, this paper reports on articulatory data recorded via an ultrasound system. Data acquired by this method are compared to simulations with an articulatory-to-acoustic model (VLAM model), described below (Boë, 1999).

This is an abstract submitted for the 7th International Conference on Speech Motor Control on the developmental changes in lingual control for vowel production in German preschoolers and schoolchildren.

In this study, we examined whether reading disordered (RD) children differ in lingual coarticulatory patterns as compared to their typically developing (TD) peers as a result of potential phonological processing deficits that often include poor phoneme segmentation skills (e.g. Bryant & Bradely, 1981), speech production errors (e.g., Mann & Foy, 2007) and slow articulation speed (e.g. Parilla et al., 2004). We tested whether German RD children at the end of the first year into primary school show weaker or stronger vowel-on-consonant coarticulation effects as compared to TD children at the same age.

In the first years of life, children differ greatly from adults in the temporal organization of their speech gestures in fluent language production. However, dissent remains as to the maturational direction of such organization. The present study sheds new light on this process by tracking the development of anticipatory vowel-to-vowel coarticulation in a cross-sectional investigation of 62 German children (from 3.5 to 7 years of age) and 13 adults. It focuses on gestures of the tongue, a complex organ whose spatiotemporal control is indispensable for speech production. The goal of the study was threefold: 1) investigate whether children as well as adults initiate the articulation for a target vowel in advance of its acoustic onset, 2) test if the identity of the intervocalic consonant matters and finally, 3) describe age-related developments of these lingual coarticulatory patterns.

(In press. Pre-final version, due to copyright) In previous research, Mutual Information (MI) was employed to quantify the physical information shared between consecutive phonological segments, based on electromagnetic articulography data (EMA). In this study, MI is extended to quantifying coarticulatory resistance (CR) versus overlap in German adult speakers using ultrasound imaging. Two measurements are tested as input to MI: 1) the highest point on the tongue body and, 2) the first coefficient of the discrete Fourier transform (DFT) of the whole tongue contour.

Purpose: This study reports on a cross-sectional investigation of lingual coarticulation in 57 typically developing German children (four cohorts from 3.5 to 7 years of age) as compared with 12 adults. It examines whether the organization of lingual gestures for intrasyllabic coarticulation differs as a function of age and consonantal context. Method: Using the technique of ultrasound imaging, we recorded movement of the tongue articulator during the production of pseudo words including various vocalic and consonantal contexts. Results: Results from linear mixed effects models show greater lingual coarticulation in all groups of children as compared to adults with a significant decrease from the kindergarten years (at 3; 4; 5) to the end of the first year into primary school (at 7). Additional differences in coarticulation degree were found across and within age groups as a function of the onset consonant identity (/b/, /d/ and /g/). Conclusions: Results support the view that although coarticulation degree decreases with age, children do not organize consecutive articulatory gestures with a uniform organizational scheme (e.g., segmental or syllabic). Instead results suggest coarticulatory organization is sensitive to the underlying articulatory properties of the segments combined.

(in press; excerpt from a non final abstract due to copyright restriction) This study reports on a cross-sectional investigation of lingual coarticulation in 57 typically developing German children (four cohorts from 3.5 to 7 years of age) as compared with 12 adults. It examines whether the organization of lingual gestures for intrasyllabic coarticulation differs as a function of age and consonantal context. Using the technique of ultrasound imaging, we recorded movement of the tongue articulator during the production of pseudo words including various vocalic and consonantal contexts. Results from linear mixed effects models show greater lingual coarticulation in all groups of children as compared to adults with a significant decrease from the kindergarten years (at 3; 4; 5) to the end of the first year into primary school (at 7). Additional differences in coarticulation degree were found across and within age groups as a function of the onset consonant identity (/b/, /d/ and /g/). Results support the view that although coarticulation degree decreases with age, children do not organize consecutive articulatory gestures with a uniform organizational scheme (e.g., segmental or syllabic). Instead results suggest coarticulatory organization is sensitive to the underlying articulatory properties of the segments combined.

Tongue movements for speech segments vary depending on their phonetic context. For adults, it has been shown that these coarticulatory effects do not only occur between adjacent segments but can span several segments in both the anticipatory and carryover direction. Moreover, especially the two directions of vowel-to-vowel (V-to-V) coarticulation are claimed to originate from different underlying processes: While articulatory planning is the driving force for anticipatory coarticulation, carryover effects mainly result from mechanical constraints and articulators' inertia (Recasens, 1987). Lingual V-to-V coarticulation has also been investigated in children to address speech motor control development. However, most acquisition studies have focused on anticipation only and were restricted to acoustic measures. With this study, we shed more light on the development of speech motor control and articulatory planning by comparing lingual V-to-V coarticulation in anticipatory and car-ryover directions across different ages using articulatory measures. We recorded 69 German children (3y, 4y, 5y, & 7y) and adults using SOLLAR, a child-friendly recording platform (Noiray, Ries, & Tiede, 2015). The technique of ultrasound imaging allowed us to trace tongue positions directly instead of inferring them from the acoustic signal. We used a symmetrical stimulus structure (ǝC1VC2ǝ) to test for influences of the me-dial vowel (/i/, /y/, /u/, /a/, /e/, /o/) on both schwas – the preceding one for anticipatory and the following one for carryover coarticulation. The intervocalic consonants varied in their coarticulatory resistance (/d/>/g/≥/b/) (Recasens, Pallarés, & Fontdevila, 1997). Congruent with Recasens' (1987) view, we hypothesized that highly resistant intervocalic consonants decrease lingual V-to-V coarticulation more extensively in the carryover than in the anticipa-tory direction. Our data indicate that all age groups exhibit substantial anticipatory as well as carryover V-to-V coarticulation. In both directions, coarticulation magnitude decreases with age. However , the decrease is stronger and more linear in anticipatory coarticulation. The intervocalic consonant plays a greater role in carryover coarticulation than in anticipatory coarticulation, but its influence on V-to-V coarticulation is not uniform across cohorts. These first results provide more evidence for the two coarticulation directions to be guided by different underlying processes. Implications for the complex development of speech production and tongue control during childhood will be discussed in further detail.

In the domain of spoken language acquisition, a large body of empirical research has focused on coarticulation mechanism, which regards the binding of articulatory gestures for neighboring phonemes. Coarticulation is an important mechanism to investigate as it engages multiple speech articulators (e.g., the lips, the tongue) whose actions must be finely coordinated in time and in the space of the vocal tract to produce fluent phonetic output in the native language. However, up to date, the development of temporal and spatial organization of speech gestures, in particular that of the tongue remains poorly understood in young children. Our study addresses this limitation by presenting a quantitative cross-sectional investigation of lingual coarticulation in German children that expands from the preschool years to the beginning of second grade. Unlike previous studies, we investigated the articulatory mechanisms from which differences in coarticulation may originate. Adapting the technique of ultrasound imaging to child study (SOLLAR, Noiray et al. 2015), we recorded movements of the main tongue articulator for vowels and consonants production in a series of C 1 VC 2 ə nonwords. We tested whether the organization of intra-syllabic coarticulatory patterns not only varies as a function of age but also depends on the articulatory demands imposed on the tongue for consecutive phonemes. To achieve these goals, we measured the coarticulation degree (CD) of the tongue body between C 1 and V using consonants (/b, d, g, z/) known in adults to vary in their coarticulatory flexibility (Fowler, 1994). Results from linear mixed effects models highlighted significant age differences in lingual coarticulation with preschoolers showing larger CD than adults. Adults displayed more fine-grained modulations of CD as a function of consonants' articulatory signature compared to children. When further examining the temporal unfolding of the coarticulatory process within the consonant, we found that the coarticulatory span decreased with age. Preschoolers exhibited a strong encroachment of the vowel with the consonant, suggesting an organization of lingual gestures that encompasses both phonemes. School-age children showed less vocalic influence over the tongue configuration within the consonant but did not yet match adults' patterns. Overall, results show that in the second school year, children do not fully control the spatial and temporal organization of lingual gestures for fluently coarticulating the phonemes of their native language. As the degree of lingual control may be tightly intertwined with children's experience with their native language, we are currently testing for effects of phonological development on coarticulatory patterns.

A successful characterization of vocal tract control during speech needs to account for regular variability in the degree of coarticulatory overlap allowed by different speech segments. While some segments allow for large degree of articulatory overlap, others show high coarticulation resistance (CR) i.g. ability to resist influence from neighbors and retain control over articulators across contexts. Despite the importance of the CR phenomenon for theories and models of speech production, a unified quantitative measure of coarticulation resistance has not been established yet. The most prominent description of CR, DAC scale (Recasens & Espinosa, 2009), has some limitations: first, it subjectively divides segments into several categories based exclusively on the degree of lingual coarticulation they exhibit across contexts. Second, this categorization is based on the measures of coarticulation that quantify only linear dependencies. Generally, a wide variety of experimental techniques and corresponding quantification methods make it difficult to directly compare CR estimates across studies. Recently, Iskarous et al. (2013) suggested measuring CR with Mutual Information (MI), or the amount of information shared by a given segment with other segments across contexts. The MI is non-parametric method that does not make assumptions about distribution but rather estimates it from data. The MI values have been shown by Iskarous et al (2013) to capture the CR effects of place and manner, as well as time differences in CR. In our study we extend the application of MI to quantifying coarticulation from ultrasound images. We investigate the effect of consonantal context on vowel-to-consonant coarticulation in German adults by looking at the position of the highest point of the tongue. Our results show that CR of German consonants exhibits the pattern /z > d > g > b/ in horizontal dimension and /z > g > d > b/ in the vertical dimension. These finding corroborates those made by Iskarous et al (2013) for German voiceless consonants for tongue body articulator using EMA data. This suggests that MI measure allows for cross-methodological comparisons and generalizations of quantitative findings. Temporal aspects of coarticulation resistance for different segments are currently being investigated by comparing MI values at different time points during consonant production. We are also applying MI to quantify whole tongue contours to compare aspects of coarticulation captured by different methods of tongue shape quantification.

The present study investigates the development of coarticulation in German children between 3 and 7 years of age. To quantify coarticulation degree, we will not only apply the commonly used method of Locus Equations (LE) on the acoustic signal, but also on the articulation recorded with ultrasound, which so far has been rarely done in children (Noiray et al., 2013). This allows us to directly track dynamic movements instead of inferring (co)articulation from the acoustic signal. Coarticulation can be viewed as connecting single speech sounds by varying degrees of articulatory overlap. While some aspects of coarticulation are claimed to be universal, resulting from anatomic properties (e.g., overlap of labial consonants and lingual vowels), others are not that predictable and may be language-specific (e.g., vowel-to-vowel coarticulation). The way children acquire the coarticulatory patterns of their native language has been discussed intensively (i.e., holistic versus segmental theory). The present study extends previous work by investigating coarticulation with a broader set of phonemes, multiple age groups, and in both acoustics and articulation. Five cohorts of monolingual German children (3 to 7 years of age) as well as an adult control group are tested. Stimuli are elicited in a repetition task embedded in a child friendly setting. The prerecorded acoustic stimuli consist of disyllabic pseudo words following the pattern C1V1C2V2, preceded by the carrier word " eine " (/͜ aɪnə/). Within the stressed first syllable (C1V1), C1 is /b/, /d/, /g/, or /z/ and V1 one of the tense, long vowels /i/, /y/, /u/, /a/, /e/, and /o/. The second CV syllable consisting of the same consonant set as C1 plus the neutral vowel /ə/ is added to the syllable of interest such that C2 is never equal to C1, resulting in three different contexts per C1V1. In total, there are 72 different pseudo words. Besides the CV coarticulation within the pseudo word, the carrier phrase enables the investigation of V-to-V anticipatory coarticulation from V1 on the preceding schwa. At Ultrafest VII we will present the first results for CV coarticulation in the cohort of 5 year-olds and adults. During the recordings, children are comfortably seated in an adjustable car seat. They are recorded with a portable ultrasound system (Sonosite Edge, sr: 48Hz) with a small probe fixed on a custom-made probe holder. The probe holder was designed to allow for natural vertical motion of the jaw but prevent motion in the lateral and horizontal translations. It is positioned straight below the participant's chin to record the tongue on the midsagittal plane. Ultrasound video data are collected with synchronized audio speech signal (microphone Sennheiser, sr: 48 KHz) on a computer. In addition to tongue motion, a video camera (Sony, sr: 50Hz) records the participant's face to track the labial articulation as well as head and probe motion enabling us to correct the data from a jaw-based to a head-based coordinate system. As for the analysis, target words in the acoustic speech signal as well as relevant tongue data are extracted using custom-made Praat and Matlab programs. Acoustic LE measures of the CV coarticulation will be based on the F2 transitions between the very onset of V1 and its midpoint, while the articulatory analysis will focus on the highest tongue point's motion between C1 and V1. As the ultrasound allows us to track motion earlier than is visible in the acoustic signal, we will not only use the onset of the vowel but move further into the consonant to find early cues of the vowel's influence on the tongue shape.

The study aims to investigate the development of coarticulation in 5-year old German children. The main goal was to examine the way different aspects of consonant production vary on a quantitative coarticulation -invariance scale as a function of age. To achieve this goal, we employed Mutual Information (MI), a method that has been used to measure coarticulation degree by quantifying independence between two variables (Iskarous et al., 2013).

This study investigates lingual V-to-V anticipatory coarticula-tion in German preschoolers and adults using ultrasound measures. In light of conflicting results in the literature, the aim was to study effects in large cohorts and with a widespread set of vowels. Results provide evidence for V-to-V coarticulation in children as well as adults, independent of the intervocalic consonant. Interestingly, coarticulation magnitude decreases with age.