Speech Development Between 30 and 119 Months in Typical Children II: Articulation Rate Growth Curves

A Preliminary Investigation of Within-Word Silent Intervals Produced by Children With and Without Neurodevelopmental Disorders

PURPOSE

The categorization of silent intervals during speech production is necessary for accurate measurement of articulation rate and pauses. The primary purpose of this preliminary study was to examine the within-word silent interval associated with the stop closure in word-final stop consonants produced by children with and without neurodevelopmental disorders.

METHOD

Seven children diagnosed with either cerebral palsy or Down syndrome (i.e., children with neurodevelopmental disorders) and eight typically developing children produced a reading passage. Participants were between the ages of 11 and 16 years. Fifty-eight words from the reading passage were identified as having word-final stop consonants. The closure duration of the word-final stop consonant was calculated, both in absolute duration and percent pause time. The articulation rate of the entire passage was calculated. The number of closure durations that met or exceeded the minimum duration threshold to be considered a pause (150 ms) was examined descriptively.

RESULTS

Children with neurodevelopmental disorders produced significantly longer closure durations and significantly slower articulation rates than typically developing children. Children with neurodevelopmental disorders produced closure durations that met or exceeded the minimum duration threshold of a pause, but typically developing children, generally, did not.

CONCLUSION

These data indicate the need to examine the location of silent intervals that meet the minimum duration threshold of a pause and correct for articulatory events during the measurement of articulation rate and pauses in children with neurodevelopmental disorders.

A case study of bilingual neurogenic stuttering: Measures of fluency, emotion, and articulation rate

INTRODUCTION

This study explores the features of bilingual neurogenic stuttering and the potential connection between emotion and articulation rate on speech disfluencies.

METHOD

The participant is  a 59-year old, Yiddish-English bilingual male with a moderate non-fluent aphasia. Thirty-two narratives (16 in each language), elicited using cue words, were analyzed for frequency of disfluency, type of disfluency (stuttering vs. non-stuttering-like), word-type (content vs. function), within-word location of disfluency, and occurrence of accessory behaviors. Additionally, the percentage and type of emotion (positive vs. negative) expressed, and articulation rate (fluent syllables spoken/duration of fluent utterances) was assessed.

RESULTS

Disfluency occurred in each language with approximately equal frequency. The most common stuttering-like disfluencies were repetitions (monosyllabic, sound, and syllable) and prolongations. The most common non-stuttering-like disfluencies were self-correction/revisions, phrase and multisyllabic word repetitions, and pauses (silent and filled). In both languages, disfluencies occurred on both content and function words, but primarily content words, and in any position of the word, although primarily initial position. No accessory behaviors were noted. There was a similar amount of emotion words used in each language although the first acquired language, L1/Yiddish, had an overall more positive tone, and his second acquired language, L2/English, had a more negative tone. Additionally, there was a negative relationship between emotion and the number of disfluencies in L1/Yiddish, and a positive relationship in L2/English. A faster articulation rate was found in his native and more proficient language, Yiddish, than English. There was a negative relationship between articulation rate and the number of disfluencies in L1/Yiddish, and a positive relationship in L2/English.

CONCLUSIONS

Cross-linguistics differences for emotion and articulation rate demonstrates that these aspects impact on fluency and contributes to the disfluencies in each language. Clinical implications of the study demonstrates the importance of assessment of bilingual (i.e., proficiency and dominance) and fluency features of each language in the diagnostic process and the significance of considering emotional processes and articulation rate as part of a comprehensive intervention plan for acquired stuttering.

Intelligibility in Context Scale: Growth Curves for Typically Developing English-Speaking Children Between Ages 2;6 and 9;11

PURPOSE

The aim of this study was to quantify the clinical utility of the Intelligibility in Context Scale (ICS) English version by characterizing the growth patterns of the ICS composite scores and seven ICS individual item scores of typically developing American English-speaking children.

METHOD

Parents of 545 typically developing children aged 2;6-9;11 (years;months) completed the ICS. Using a proportional odds model, we regressed ICS composite scores on age and computed for model-estimated mean and lower quantile ICS composite scores. Logistic regression and proportional odds modeling were utilized to quantify the relationship of individual ICS items and age.

RESULTS

ICS composite scores of typically developing children changed with age, but change was small and incremental, with scores compressed between 3 and 5 across the range of ages. An average child (i.e., on the 50th percentile) is expected to have an ICS composite score of 4 beginning at 3;0 and an ICS composite score of 5 by 6;6. On average, parents gave different intelligibility ratings based on communicative partners, and the rating differences between communicative partners decreased with age.

CONCLUSIONS

Given that ICS scores increase with age, the expected score for average children also increases. A child's age is a main factor for interpreting ICS scores.

Developmental Cut-Points for Atypical Speech Intelligibility in Children With Cerebral Palsy

PURPOSE

Early identification of speech motor involvement (SMI) in children with cerebral palsy (CP) is difficult because of overlapping features with many aspects of typical speech development. Quantitative measures of speech intelligibility have the potential to differentiate between children with SMI and those with no SMI (NSMI). We examined thresholds for speech intelligibility development in children with CP relative to the low end of age-specific typical developmental expectations. We sought to determine whether there were intelligibility differences between children with CP and NSMI versus typically developing (TD) age-mates across the range of development and whether there were differences between children with CP who have NSMI and those with CP who have SMI across the range of development based on speech intelligibility.

METHOD

We used two large existing data sets that included speech samples from children between the ages of 2.5 and 8 years. One data set included 511 longitudinal speech samples from children with CP; the other included 505 cross-sectional speech samples from TD children. We examined receiver operating characteristic curves and sensitivity/specificity results by age for differentiating among groups of children.

RESULTS

TD children versus those with CP and NSMI showed differentiation in their speech intelligibility across all ages, but the strength of differentiation was only marginally above chance. Children with CP and NSMI showed clear differentiation in their speech intelligibility from those with CP and SMI beginning at the earliest age point. Children with CP who have intelligibility below 40% at the age of 3 years have a very high probability of having SMI.

CONCLUSIONS

Early intelligibility screening should be performed in children diagnosed with CP. Those with intelligibility below 40% at 3 years of age should be referred immediately for speech assessment and treatment.

Differential Impacts of Sentence Length on Speech Rate in Two Groups of Children With Neurodevelopmental Disorders

PURPOSE

The primary purpose of this study was to examine the effect of sentence length on speech rate and its characteristics, articulation rate, and pauses in children with neurodevelopmental disorders.

METHOD

Nine children diagnosed with cerebral palsy (CP) and seven children diagnosed with Down syndrome (DS) repeated sentences varying in length from two to seven words. Children were between the ages of 8 and 17 years. Dependent variables included speech rate, articulation rate, and proportion of time spent pausing.

RESULTS

For children with CP, there was a significant effect of sentence length for speech rate and articulation rate but not for the proportion of time spent pausing. In general, the longest sentences were produced with a faster speech and articulation rate than the shortest sentences. For children with DS, there was a significant effect of sentence length for the proportion of time spent pausing but not for speech rate or articulation rate. In general, children with DS spent significantly more time pausing in the longest sentences, particularly seven-word sentences, than in any other sentence length.

CONCLUSIONS

Primary findings include the following: (a) Articulation rate and pause time are differentially impacted by sentence length, and (b) children with CP and children with DS respond differently to increases in cognitive-linguistic load.

A Descriptive Study of Speech Breathing in Children With Cerebral Palsy During Two Types of Connected Speech Tasks

PURPOSE

This study examined speech breathing during two connected speech tasks in children with cerebral palsy (CP) and typically developing (TD) peers. Understanding how the respiratory system supports speech production during various speech tasks can help researchers construct appropriate models of speech production and clinicians remediate speech disorders effectively.

METHOD

Four children with CP and four age- and sex-matched TD peers completed two speech tasks, reading and extemporaneous speech. Respiratory kinematic and acoustic data were collected. Dependent variables included utterance length, speech rate, sound pressure level, and lung volume variables.

RESULTS

Based on descriptive results, children with CP and speech motor involvement demonstrated reduced utterance length and speech rate, equivalent intensity levels, and changes in lung volume variables indicative of respiratory physiological impairment as compared to their TD peers. However, children with CP and no speech motor involvement exhibited speech production and speech breathing variables in the more typical range. In relation to task effects, the majority of children (CP and TD) produced shorter utterances, slower speech rates, equivalent intensity levels, higher lung volume initiation, termination, excursion, higher percent vital capacity per syllable, and longer inspiratory duration during extemporaneous speech as compared to reading.

CONCLUSIONS

Two major themes emerged from the data: (a) Children with CP, particularly those with concomitant speech motor involvement, demonstrate different speech production and speech breathing patterns than their TD peers. (b) Speech task impacts speech production and speech breathing variables in both children with CP and their TD peers, but the extemporaneous speech task did not seem to exaggerate group differences.

Prosodic Development During the Early School-Age Years

PURPOSE

This study used a cross-sequential design to identify developmental changes in narrative speech rhythm and intonation. The aim was to provide a robust, clinically relevant characterization of normative changes in speech prosody across the early school-age years.

METHOD

Structured spontaneous narratives were elicited annually from 60 children over a 3-year period. Children were aged 5-7 years at study outset and then were aged 7-9 years at study offset. Articulation rate, prominence spacing, and intonational phrase length and duration were calculated for each narrative to index speech rhythm; measures of pitch variability and pitch range indexed intonation. Linear mixed-effects (LME) models tested for cohort-based and within-subject longitudinal change on the prosodic measures; linear regression was used to test for the simple effect of age-in-months within year on the measures.

RESULTS

The LME analyses indicated systematic longitudinal changes in speech rhythm across all measures except phrase duration; there were no longitudinal changes in pitch variability or pitch range across the school-age years. Linear regression results showed an increase in articulation rate with age; there were no systematic differences between age cohorts across years in the study.

CONCLUSIONS

The results indicate that speech rhythm continues to develop during the school-age years. The results also underscore the very strong relationship between the rate and rhythm characteristics of speech and so suggest an important influence of speech motor skills on rhythm production. Finally, the results on pitch variability and pitch range are interpreted to suggest that these are inadequate measures of typical intonation development during the school-age years.

Intelligibility, Speech Rate, and Communication Efficiency in Children With Neurological Conditions: A Longitudinal Study of Childhood Dysarthria

PURPOSE

This study aimed to describe communication-related parameters (i.e., intelligibility, speech rate, and communication efficiency) and their developmental courses in children with neurological conditions against the background of typical development. In addition, interrelations between the developmental courses of communication-related parameters and auditory-perceptual ratings related to speech subsystems were investigated.

METHOD

Fourteen children with neurological conditions (CNC) and 14 typically developing children (CTD), matched for age and gender (four girls; 5;1-8;4 [years;months] at first examination), were assessed at three points in time over an 18-month period. Speech samples were collected using the Bogenhausener Dysarthrie Skalen-Kindliche Dysarthrien (English: Bogenhausen Dysarthria Scales-Childhood Dysarthria), a German tool for the assessment of childhood dysarthria. To assess intelligibility, naïve listeners transcribed audio samples of sentence repetitions of the children. Speech rate was measured by acoustic analyses, and communication efficiency was determined by multiplying the proportion of correctly transcribed syllables with speech rate. Age normalization was performed following a recently published approach.

RESULTS

On the group level, CNC had conspicuous raw and normalized scores for the three communication-related parameters and were more variable than the CTD group regarding their developmental courses. These differences were more pronounced for intelligibility than for speech rate. A strong relationship between communication-related and speech subsystems-related auditory-perceptual characteristics was apparent only between intelligibility and articulation/resonance.

CONCLUSIONS

For the first time, age-normalized scores for communication-related parameters were reported in children with neurological disorders and put into a developmental context within the framework of a longitudinal study. Age-normalized intelligibility was more vulnerable to large developmental changes than speech rate and was best predicted by changes in articulation and resonance. Overall, this study may contribute to a more comprehensive and valid clinical assessment of childhood dysarthria and to a better understanding of its developmental dynamics.