Introducing WCM-SE: The word complexity measure phonetically justified and adapted to Swedish

Speech sound development of young Dutch children with a developmental language disorder: A complex matter

BACKGROUND

Approximately 50% of all young children with a developmental language disorder (DLD) also have problems with speech production. Research on speech sound development and clinical diagnostics of speech production difficulties focuses mostly on accuracy; it relates children's phonological realizations to adult models. Contrarily to these relational analyses, independent analyses indicate the sounds and structures children produce irrespective of accuracy. Such analyses are likely to provide more insight into a child's phonological strengths and limitations, and may thus provide better leads for treatment.

AIMS

Ram (1) To contribute to a more comprehensive overview of the speech sound development of young Dutch children with DLD by including independent and relational analyses, (2) to develop an independent measure to assess these children's speech production capacities; and (3) to examine the relation between independent and relational speech production measures for children with DLD.

METHODS & PROCEDURES

We describe the syllable structures and sounds of words elicited in two picture-naming tasks of 82 children with DLD and speech production difficulties between ages 2;7 and 6;8. The children were divided into four age groups to examine developmental patterns in a cross-sectional manner. Overviews of the children's productions on both independent and relational measures are provided. We conducted a Spearman correlation analysis to examine the relation between accuracy and independent measures.

OUTCOMES & RESULTS

The overviews show these children are able to produce a greater variety of syllable structures and consonants irrespective of target positions than they can produce correctly in targets. This is especially true for children below the age of 4;5. The data indicate that children with DLD have difficulty with the production of clusters, fricatives, liquids and the velar nasal (/ŋ/). Based on existing literature and our results, we designed a Dutch version of an independent measure of word complexity, originally designed for English (word complexity measure-WCM) in which word productions receive points for specific word, syllable and sound characteristics, irrespective of accuracy. We found a strong positive correlation between accuracy scores and scores on this independent measure.

CONCLUSIONS & IMPLICATIONS

The results indicate that the use of independent measures, including the proposed WCM, complement traditional relational measures by indicating which sounds and syllable structures a child can produce (irrespective of correctness). Therefore, the proposed measure can be used to monitor the speech sound development of children with DLD and to better identify treatment goals, in combination with existing relational measures.

WHAT THIS PAPER ADDS

What is already known on the subject Speech production skills can be assessed in different ways: (1) using analyses indicating the structures and sounds a child produces irrespective of accuracy, that is, performance analyses; and (2) using analyses indicating how the productions of a child relate to the adult targets, that is, accuracy analyses. In scientific research as well as in clinical practice the focus is most often on accuracy analyses. As a consequence, we do not know if children who do not improve in accuracy scores, improve in other phonological aspects that are not captured in these analyses, but can be captured by performance analyses. What this study adds to the existing knowledge The overviews show these children are able to produce a greater variety of syllable structures and consonants irrespective of target positions than they can produce correctly in targets. Consequently, adding performance analyses to existing accuracy analyses provides a more complete picture of a child's speech sound development. What are the potential or actual clinical implications of this work? We propose a Dutch version of a WCM, originally designed for English, in which word productions receive points for word structures, syllable structures and sounds, irrespective of accuracy. This measure may be used by Dutch clinicians to monitor the speech sound development of children with DLD and to formulate better treatment goals, in addition to accuracy measures that are already used.

Expressive vocabulary intervention for four 2- to 3-year-old children with cerebral palsy and speech/language difficulties: A single-case A-B study

PURPOSE

To evaluate a parent-delivered expressive vocabulary intervention using focused stimulation for young children with cerebral palsy (CP).

METHOD

A single case A-B design was used. Use of expressive target words was evaluated during the baseline (A) and intervention (B) phases. Untrained expressive words were used as control behaviour. Four 2- to 3-year-old boys with CP and their parents participated. All participants had an expressive vocabulary of less than 50 words at study intake. Following training, parents delivered the intervention daily at home for 5 weeks. Generalisation of the intervention was measured with a parent-rated vocabulary checklist.

RESULT

Two participants showed clear gains and one participant showed a smaller gain in target words. Two of these three participants did not improve on control words, but one participant increased his use of both target and control words. One participant did not increase his use of either control or target words. All participants improved on parent-reported expressive vocabulary, and for two children, improvements were large.

CONCLUSION

Parent-delivered focused stimulation may lead to gains in expressive vocabulary in children with CP and speech and language difficulties. The intervention would be suitable for larger single-case studies with more experimental control.

The Effects of Phonological Complexity on Word Production in French-Speaking Children

Word complexity indices, such as the Index of Phonetic Complexity (IPC) and the Word Complexity Measure (WCM), code a word in terms of featural and structural properties that pose difficulty in phonological development. Studies have investigated the influence of complexity indices on vocabulary development; however, few have examined their influence on consonant accuracy. Furthermore, these indices were developed for English-speaking children and have not been widely applied to other languages. This study investigates whether a word's phonological complexity influences how accurately it is produced in French-speaking children. Four databases consisting of the productions of children (n = 74), aged 1;11 to 4;9, were analyzed. Words were coded in terms of the IPC, WCM, and parameters that add complexity during phonological development. Using mixed-effects logistic regression, we examined whether phonological complexity as determined by the IPC, WCM, or by alternative indices better accounts for the influence of complexity on production. We also investigated whether the accuracy of a target sound/structure was influenced by a word's complexity. Results indicated that complexity based on the IPC or WCM significantly influenced consonant accuracy; however, indices tapping fewer features provided superior model fit. At younger ages, the presence of fricatives/liquids and, at all ages, the presence of alveopalatal fricatives, codas, and clusters significantly influenced accuracy. Findings were inconclusive as to whether whole word complexity influenced the accuracy of a target sound/structure. Results suggest that current complexity indices provide only approximate indications of how featural and structural properties of words influence production.

Expressive vocabulary development in children with moderate hearing loss - the impact of auditory variables and early consonant production

In this study, the early expressive vocabulary development was investigated in a group of children with moderate hearing loss (HL). Size and development of expressive vocabulary from 18 30 months were analyzed and compared to a group of children with normal hearing (NH). For the children with HL, the impact of auditory variables on number of words were examined. The relationship of early consonant production to number of words produced of both groups were examined and the phonological complexity of reported words was compared between the groups. The results showed that children with HL (n = 8) produced a similar number of words as the NH (n = 8) at 18 months, but fewer at 24 and 30 months. Hours of HA use showed significant correlations to number of words. The number of different true consonants at 18 months for the whole group showed a significant relationship to number of words produced at 24 months. No significant differences were found between children with HL and NH children regarding phonological complexity of reported words. The findings indicate that the children born with moderate HL who were fitted with hearing aids (HAs) before 6 months of age are at risk in their development of expressive vocabulary. Full-time use of HAs and monitoring of early consonant use should be encouraged in the early intervention of this target group.

Simulating Speech Error Patterns Across Languages and Different Datasets

Children's speech acquisition is influenced by universal and language-specific forces. Some speech error patterns (or phonological processes) in children's speech are observed in many languages, but the same error pattern may have different effects in different languages. We aimed to explore phonological effects of the same speech error patterns across different languages, target audiences and discourse modes, using a novel method for large-scale corpus investigation. As an additional aim, we investigated the face validity of five different phonological effect measures by relating them to subjective ratings of assumed effects on intelligibility, as provided by practicing speech-language pathologists. Six frequently attested speech error patterns were simulated in authentic corpus data: backing, fronting, stopping, /r/-weakening, cluster reduction and weak syllable deletion-each simulation resulting in a "misarticulated" version of the original corpus. Phonological effects were quantified using five separate metrics of phonological complexity and distance from expected target forms. Using Swedish child-speech data as a reference, phonological effects were compared between this reference and a) child speech in Norwegian and English, and b) data representing different modes of discourse (spoken/written) and target audiences (adults/children) in Swedish. Of the speech error patterns, backing-the one atypical pattern of those included-was found to cause the most detrimental effects, across languages as well as across modes and speaker ages. However, none of the measures reflects intuitive rankings as provided by clinicians regarding effects on intelligibility, thus corroborating earlier reports that phonological competence is not translatable into levels of intelligibility.

Relationship Between Parent Vowel Hyperarticulation in Infant-Directed Speech and Infant Phonetic Complexity on the Level of Conversational Turns

When speaking to infants, parents typically use infant-directed speech, a speech register that in several aspects differs from that directed to adults. Vowel hyperarticulation, that is, extreme articulation of vowels, is one characteristic sometimes found in infant-directed speech, and it has been suggested that there exists a relationship between how much vowel hyperarticulation parents use when speaking to their infant and infant language development. In this study, the relationship between parent vowel hyperarticulation and phonetic complexity of infant vocalizations is investigated. Previous research has shown that on the level of subject means, a positive correlational relationship exists. However, the previous findings do not provide information about the directionality of that relationship. In this study the relationship is investigated on a conversational turn level, which makes it possible to draw conclusions on whether the behavior of the infant is impacting the parent, the behavior of the parent is impacting the infant, or both. Parent vowel hyperarticulation was quantified using the vhh-index, a measure that allows vowel hyperarticulation to be estimated for individual vowel tokens. Phonetic complexity of infant vocalizations was calculated using the Word Complexity Measure for Swedish. Findings were unexpected in that a negative relationship was found between parent vowel hyperarticulation and phonetic complexity of the immediately following infant vocalization. Directionality was suggested by the fact that no such relationship was found between infant phonetic complexity and vowel hyperarticulation of the immediately following parent utterance. A potential explanation for these results is that high degrees of vowel hyperarticulation either provide, or co-occur with, large amounts of phonetic and/or linguistic information, which may occupy processing resources to an extent that affects production of the next vocalization.

An Association Between Phonetic Complexity of Infant Vocalizations and Parent Vowel Hyperarticulation

Extreme or exaggerated articulation of vowels, or vowel hyperarticulation, is a characteristic commonly found in infant-directed speech (IDS). High degrees of vowel hyperarticulation in parent IDS has been tied to better speech sound category development and bigger vocabulary size in infants. In the present study, the relationship between vowel hyperarticulation in Swedish IDS to 12-month-old and phonetic complexity of infant vocalizations is investigated. Articulatory adaptation toward hyperarticulation is quantified as difference in vowel space area between IDS and adult-directed speech (ADS). Phonetic complexity is estimated using the Word Complexity Measure for Swedish (WCM-SE). The results show that vowels in IDS was more hyperarticulated than vowels in ADS, and that parents' articulatory adaptation in terms of hyperarticulation correlates with phonetic complexity of infant vocalizations. This can be explained either by the parents' articulatory behavior impacting the infants' vocalization behavior, the infants' social and communicative cues eliciting hyperarticulation in the parents' speech, or the two variables being impacted by a third, underlying variable such as parents' general communicative adaptiveness.

Range of motion (ROM) in the lips and jaw during vowels assessed with 3D motion analysis in Swedish children with typical speech development and children with speech sound disorders

PURPOSE

The aim was to compare movement patterns of lips and jaw in lateral, vertical and anteroposterior directions during vowel production in children with typical speech development (TSD) and in children with speech sound disorders (SSD) persisting after the age of six.

METHODS

A total of 93 children were included, 42 children with TSD (6:0-12:2 years, mean age 8:9 ± 1:5, 19 girls and 23 boys) and 51 children with SSD (6:0-16:7 years, mean age 8:5 ± 3:0, 14 girls and 37 boys). Range of motion (ROM) in lips and jaw in the vowels [a, ʊ, ɪ] produced in a syllable repetition task and median values in resting position were measured with a system for 3D motion analysis. The analysis was based on the coordinates for the mouth corners and the chin centre.

RESULTS

There were significant differences between the groups on movements in lateral direction in both lips and jaw. Children with TSD had generally smaller and more, symmetrical movements in the lips and jaw, in all three dimensions compared to children with SSD. There were no significant differences between the groups in resting position.

CONCLUSION

Children with SSD persisting after the age of six years show more asymmetrical and more variable movement patterns in lips and jaw during vowel production compared with children with TSD in a simple syllable repetition task. Differences were more pronounced in lateral direction in both lips and jaw.