Speaking Rate Effects on Locus Equation Slope

A locus equation describes a 1st order regression fit to a scatter of vowel steady-state frequency values predicting vowel onset frequency values. Locus equation coefficients are often interpreted as indices of coarticulation. Speaking rate variations with a constant consonant–vowel form are thought to induce changes in the degree of coarticulation. In the current work, the hypothesis that locus slope is a transparent index of coarticulation is examined through the analysis of acoustic samples of large-scale, nearly continuous variations in speaking rate. Following the methodological conventions for locus equation derivation, data pooled across ten vowels yield locus equation slopes that are mostly consistent with the hypothesis that locus equations vary systematically with coarticulation. Comparable analyses between different four-vowel pools reveal variations in the locus slope range and changes in locus slope sensitivity to rate change. Analyses across rate but within vowels are substantially less consistent with the locus hypothesis. Taken together, these findings suggest that the practice of vowel pooling exerts a non-negligible influence on locus outcomes. Results are discussed within the context of articulatory accounts of locus equations and the effects of speaking rate change

Statistical analysis of word-initial /k/ and /t/ produced by normal and phonologically disordered children

The acoustic characteristics of voiceless velar and alveolar stop consonants were investigated for normally articulating and phonologically disordered children using spectral moments. All the disordered children were perceived to produce It/ for /k/, with /k/ being absent from their phonetic inventories. Approximately 82% of the normally articulating children's consonants were classified correctly by discriminant function analysis, on the basis of the mean (first moment), skewness (third moment) and kurtosis (fourth moment) derived from the first 40 ms of the VOT interval. When the discriminant function developed for the normally articulating children was applied to the speech of the phonologically disordered group of children, no distinction was made between the velar and alveolar stops. Application of the model to the speech of individual children in the disordered group revealed that one child produced distinct markings to the velar-alveolar contrast. Variability measures of target /t/ and /k/ utterances indicated greater variability in this disordered child's productions compared with the normally articulating children. Phonological analysis of this child's speech after treatment, in which the velar-alveolar contrast was not treated, revealed target appropriate productions of both It/ and /k/. By contrast, the other three phonologically disordered children, for whom no acoustic distinction was found between target It/ and target /k/, did not evidence any knowledge of the contrast after treatment with other target phonemes.National Institutes of Health DC00433, RR7031K, DC00076, DC001694 (PI: Gierut)This is an Accepted Manuscript of an article published by Taylor & Francis in Clinical Linguistics & Phonetics on January 1990, available online: http://wwww.tandfonline.com/10.1080/026992000750020341

A computational simulation of children's performance across three nonword repetition tests

The nonword repetition test has been regularly used to examine children’s vocabulary acquisition, and yet there is no clear explanation of all of the effects seen in nonword repetition. This paper presents a study of 5-6 year-old children’s repetition performance on three nonword repetition tests that vary in the degree of their lexicality. EPAM-VOC, a model of children’s vocabulary acquisition, is then presented that captures the children’s performance in all three repetition tests. The model represents a clear explanation of how working memory and long-term lexical and sub-lexical knowledge interact in a way that is able to simulate repetition performance across three nonword tests within the same model and without the need for test specific parameter settings

Gesture production and comprehension in children with specific language impairment

Children with specific language impairment (SLI) have difficulties with spoken language. However, some recent research suggests that these impairments reflect underlying cognitive limitations. Studying gesture may inform us clinically and theoretically about the nature of the association between language and cognition. A total of 20 children with SLI and 19 typically developing (TD) peers were assessed on a novel measure of gesture production. Children were also assessed for sentence comprehension errors in a speech-gesture integration task. Children with SLI performed equally to peers on gesture production but performed less well when comprehending integrated speech and gesture. Error patterns revealed a significant group interaction: children with SLI made more gesture-based errors, whilst TD children made semantically based ones. Children with SLI accessed and produced lexically encoded gestures despite having impaired spoken vocabulary and this group also showed stronger associations between gesture and language than TD children. When SLI comprehension breaks down, gesture may be relied on over speech, whilst TD children have a preference for spoken cues. The findings suggest that for children with SLI, gesture scaffolds are still more related to language development than for TD peers who have out-grown earlier reliance on gestures. Future clinical implications may include standardized assessment of symbolic gesture and classroom based gesture support for clinical groups

A Kinematic Description of the Temporal Characteristics of Jaw Motion for Early Chewing: Preliminary Findings

Purpose: The purpose of this investigation was to describe age- and consistency-related changes in the temporal characteristics of chewing in typically developing children between the ages of 4 and 35 months and adults using high-resolution optically based motion capture technology. Method: Data were collected from 60 participants (48 children, 12 adults) across 5 age ranges (beginners, 7 months, 12 months, 35 months, and adults); each age group included 12 participants. Three different food consistencies were trialed as appropriate. The data were analyzed to assess changes in chewing rate, chewing sequence duration, and estimated number of chewing cycles. Results: The results revealed both age- and consistency-related changes in chewing rate, sequence duration, and estimated number of chewing cycles, with consistency differences affecting masticatory timing in children as young as 7 months of age. Chewing rate varied as a function of age and consistency, and chewing sequence duration was shorter for adults than for children regardless of consistency type. In addition, the results from the estimated number of chewing cycles measure suggest that chewing effectiveness increased with age; this measure was also dependent on consistency type. Conclusions: The findings suggest that the different temporal chewing variables follow distinct developmental trajectories and are consistency dependent in children as young as 7 months of age. Clinical implications are detailed

Statistical Representation of Word-Initial Obstruents - Adult Data

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Some typological properties of functional misarticulation systems

National Institutes of Health DC00433, RR7031K, DC00076, DC001694 (PI: Gierut

Spectral analysis of target-appropriate /t/ and /k/ produced by phonologically disordered and normally articulating children

Previous research (Forrest, Weismer, Hodge, Dinnsen and Elbert, 1990) has shown that some phonologically disordered children differentially mark seemingly homophonous phonemes; however, the resulting contrast may be spectrally distinct from that produced by normally articulating children of the same age. In the present investigation possible sources for these differences between normally articulating and phonologically disordered children's productions of target-appropriate phonemes were pursued. Spectral characteristics of seemingly correct productions of /t/ and /k/ in word-initial position were analysed for four normally articulating and seven phonologically disordered children to assess the effect of recency of acquisition, depth of knowledge of the contrast and/or the effect of a phonological disorder on accuracy and variability of production. Results revealed that children who had acquired the velar-alveolar contrast more recently, and who had incomplete knowledge of that contrast, produced target-appropriate /t/ and /k/ differently from their normally articulating peers and other phonologically disordered children with greater knowledge of the contrast. Further, the phonologically disordered children with incomplete knowledge of the velar-alveolar contrast were less variable than the other phonologically disordered or normally articulating children in the spectral characteristics across repeated productions. Analysis of the spectral characteristics of word-initial /t/ and /k/ at a later point in time indicated similarities between all speaker groups in the spectral parameters that distinguished the velar from the alveolar stop. However, the stability of these parameters across repeated productions decreased for the phonologically disordered children with greater knowledge of the contrast. These effects are related to motor skill development and found to be consistent with previously demonstrated patterns of skill acquisition.National Institutes of Health DC00433, RR7031K, DC00076, DC001694 (PI: Gierut)This is an Accepted Manuscript of an article published by Taylor & Francis in Clinical Linguistics & Phonetics on January 1994, available online: http://wwww.tandfonline.com/10.3109/02699209408985312