The Composition of Early Vocabulary in Spanish Children With Down Syndrome and Their Peers With Typical Development

The role of imageability in noun and verb acquisition in children with Down syndrome and their peers with typical development

Our main objective was to analyze the role of imageability in relation to the age of acquisition (AoA) of nouns and verbs in Spanish-speaking children with Down syndrome (DS) and their peers with typical development (TD). The AoA of nouns and verbs was determined using the MacArthur-Bates CDIs adapted to the profile of children with DS. The AoA was analyzed using a linear mixed-effect model, including factors of imageability, group, and word class, and controlling for word frequency and word length. This analysis showed that high imaginable and short words were acquired early. Children with DS acquired the words later than TD peers. An interaction between imageability and group indicated that the effect of imageability was greater in the DS group. We discuss this effect considering DS children's phonological memory difficulties. The overall results confirm the role that imageability and word length play in lexical acquisition, an effect that goes beyond word class.

Word type and modality in the emerging expressive vocabularies of preschool children with Down syndrome

BACKGROUND

Previous studies have explored the size and word type composition (nouns, predicates, etc.) of expressive vocabularies of preschool children with Down syndrome, both spoken and signed. Separately, overall preferences for modality of expression have also been explored.

AIMS

To extend previous findings by describing the relationships between expressive vocabulary size and both word type and modality of expression in the preschool period including changes to modality preference over time.

METHODS & PROCEDURES

Mothers of 35 children with Down syndrome, aged 36-66 months and attending the same early intervention programme, completed a version - with both spoken word and sign options - of the New Zealand MacArthur-Bates Communicative Development Inventory (CDI): Words and Sentences. Most mothers completed the CDI on multiple occasions across the duration of the study. Completions (n = 114) were analysed cross-sectionally and longitudinally in terms of (1) word type relative to vocabulary size, (2) modality of expression relative to word type and vocabulary size, and (3) individual trajectories in vocabulary size and modality of expression.

OUTCOMES & RESULTS

(1) Word type relative to vocabulary size was similar to previous studies with a greater proportion of the SOCIAL words being present in the children's vocabularies throughout, followed by NOUNS, PREDICATES and CLOSED class words, with proportions converging as vocabulary sizes increase. (2) An initial spoken word preference for SOCIAL and CLOSED class words and sign preference for NOUNS and PREDICATES was found, with more spoken words in larger vocabularies overall. (3) Individual trajectories were highly variable and also revealed temporary points of regression in overall expressive vocabulary size in some children. Children who shifted from reliance on sign to predominantly spoken word expression did so at different ages and at different vocabulary sizes. At school entry, while most of the children used both modalities, some children continued to rely on sign for most vocabulary items whereas others used only spoken words.

CONCLUSIONS & IMPLICATIONS

An appreciation of both the general trends and potential for individual variation in vocabulary structure, modality of expression and change over time will better position clinicians and education specialists to provide individually tailored support to both preschool and school-aged children with Down syndrome.

WHAT THIS STUDY ADDS

What is already known on this subject Preschool children with Down syndrome have been shown to demonstrate developmental patterns in overall conceptual vocabulary size and word type development broadly similar to typical development. The use of signed vocabulary has also been explored, but independently from word type development and with less attention to individual trajectories in either vocabulary size development or modality preferences throughout the preschool period than is necessary for clinical use. What this paper adds to existing knowledge This study found interactions between word type and modality of expression in relation to vocabulary size as well as a few temporary vocabulary size regressions similar to those found in much younger typically developing children. An initial spoken word preference for social and closed class words, and sign preference for nouns and predicates, was followed by a general trend towards spoken words for all word types as vocabulary (with some fluctuations) increased over time. Children demonstrated considerable individual variation in size of vocabulary and age at which they pivoted from a signed to a spoken word preference. Moreover, while most children used both modalities at school entry, a few retained a sign-only vocabulary and others had moved fully onto spoken word-only expression. What are the potential or actual clinical implications of this work? An understanding of both the general trends and individual variation in vocabulary structure and modality of expression development will better position clinicians and educational specialists to provide individually tailored support to children with Down syndrome.

Study of a set of reading precursors among Chilean children with Down syndrome

Learning to read for children with Down syndrome is relevant because of the impact this ability has on learning and the development of autonomy. Previous research has described reading development in this population, but it is not clear if the process and precursors are the same in a transparent language like Spanish. This study explores performance in a set of precursors (phonological awareness, visual recognition, vocabulary, letter knowledge and verbal reasoning) in 42 children with Down syndrome between 6:0 and 10:11 years. We hypothesized that the participants would have a lower performance than previously reported with children with typical development, particularly in tasks of phonological awareness, because the method for reading instruction in Chile with this population is usually the global method. Our results show that the precursors improve with age, that there are differences in performance between the skills assessed, and the ceiling effect was not observed as would be expected for children with typical development for the abilities assessed at these ages, which suggests that in the children assessed the precursors are not consolidated at these ages. These results suggest that the stimulation of phonological awareness and other reading precursors in children with Down syndrome is important for reading development.

Word prediction using closely and moderately related verbs in Down syndrome

People with Down syndrome (DS) have several difficulties in language learning, and one of the areas most affected is language production. Theoretical frameworks argue that prediction depends on the production system. Yet, people with DS can predict upcoming nouns using semantically related verbs. Possibly, prediction skills in people with DS are driven by their associative mechanism rather than by the prediction mechanism based on the production system. This study explores prediction mechanisms in people with DS and their relationship with production skills. Three groups were evaluated in a preferential-looking task: young adults, children with DS, and a typically developing control group paired by sex and mental age. Participants saw two images, a target and a distractor. They also heard a sentence in one of the three conditions: with a verb that was closely related to the object (e.g., "The woman read the book"), with a verb that was moderately related to the object (e.g., "My uncle waited for the bus"), or with a verb that was unrelated to the object (e.g., "My sister threw a broom"). Their productive vocabulary was then measured. In the young adult and typically developing groups, the results showed prediction in sentences with highly and moderately related verbs. Participants with DS, however, showed prediction skills only in the highly related context. There was no influence of chronological age, mental age, or production on prediction skills. These results indicate that people with DS base prediction mainly on associative mechanisms and they have difficulty in generating top-down predictions.

Differences and Similarities in Predictors of Expressive Vocabulary Development between Children with Down Syndrome and Young Typically Developing Children

The purpose of this study was to examine potential differences in the predictors of expressive vocabulary development between children with Down syndrome and typically developing children to support preparation for intervention development. An age cohort of 43 children with Down syndrome and 57 typically developing children with similar nonverbal mental age levels were assessed at three time points. Linear mixed models were used to investigate the predictors of expressive vocabulary over time. Both groups achieved progress in expressive vocabulary. The typically developing children had steeper growth than the children with Down syndrome (1.38 SD vs. 0.8 SD, p < 0.001). In both groups, receptive vocabulary, auditory memory, and the home literacy environment were significant predictors of development. In the children with Down syndrome, the phonological awareness and oral motor skills were also significant. Group comparisons showed that receptive vocabulary, auditory memory and oral motor skills were stronger predictors in the children with Down syndrome than in the typically developing children. These results indicate that children with Down syndrome are more vulnerable when it comes to risk factors that are known to influence expressive vocabulary than typically developing children. Children with Down syndrome therefore require early broad-based expressive vocabulary interventions.

Joint attention and vocabulary development in toddlers with Down syndrome and their peers with typical development: The role of maternal interactive style

PURPOSE

Joint attention is considered a prerequisite for language development. Although language is one of the most impaired domains in Down syndrome (DS), few studies have examined the relationship between caregiver behavior during episodes of joint attention and vocabulary development in these children. Consequently, our primary aim was to analyze the behaviors of caregivers of children with DS and of children with typical development (TD) in the early stages of vocabulary development. A second objective was to examine the kind of words that caregivers use to refer to the object that is the focus of attention. We also consider the concurrent relationship between joint attention and vocabulary development in both groups of children.

METHOD

We studied 28 children with DS and 28 children with TD, individually matched on mental age and gender, and their respective caregivers. The mean mental age for children with DS and children with TD was around 12 months. The mean chronological age of caregivers of children with DS and children with TD was around 35 years. Each child and his or her caregiver were video-recorded during a free-play session involving different objects.

RESULTS

Although the total time engaged in joint attention was greater among caregivers of children with DS, caregivers of both groups of children were more likely to direct than follow their child's attentional focus. The caregivers of children with DS used a greater number of appropriate terms to refer to the object of attention. We found no significant correlation in either group of children between vocabulary development and joint attention behaviors.

CONCLUSIONS

The results may be due to the fact that the children studied are still very young in developmental terms and have yet to develop all the skills required for joint attention. At this early stage, directing the child's attention would promote the development of joint attention. A possible explanation for the lack of a correlation between vocabulary development and joint attention is that children may use an associative mechanism in the early stages of lexical learning, and hence the learning of new words is a slow process.

Verb-mediated anticipatory eye movements in people with Down syndrome

BACKGROUND

Children and adults with neurotypical development employ linguistic information to predict and anticipate information. Individuals with Down syndrome (DS) have weaknesses in language production and the domain of grammar but relative strengths in language comprehension and the domain of semantics. What is not clear is the extent to which they can use linguistic information, as it unfolds in real time, to anticipate upcoming information correctly.

AIMS

To investigate whether children and young people with DS employ verb information to predict and anticipate upcoming linguistic information.

METHODS & PROCEDURES

A preferential looking task was performed, using an eye-tracker, with children and teenagers with DS and a typically developing (TD) control group matched by sex and mental age (average = 5.48 years). In each of 10 trials, two images were presented, a target and a distractor, while participants heard a phrase that contained a semantically informative verb (e.g., 'eat') or an uninformative verb (e.g., 'see').

OUTCOMES & RESULTS

Both DS and TD control participants could anticipate the target upon hearing an informative verb, and prediction skills were positively correlated with mental age in those with DS.

CONCLUSIONS & IMPLICATIONS

This work demonstrates for the first time that children and teenagers with DS can predict linguistic information based on semantic cues from verbs, and that sentence processing is driven by predictive relationships between verbs and arguments, as in children with typical development. Clinicians can take advantage of these prediction skills, using them in therapy to support weaker areas.

Verb production by individuals with Down syndrome during narration

BACKGROUND

Despite research identifying verb knowledge as a strong predictor of later syntactic skills in typical development, virtually no research has examined verb development in Down syndrome.

AIMS

The purpose of this study was to examine verb production (density, diversity, and type-token ratios) by individuals with Down syndrome in the context of story generation relative to two comparison groups - nonverbal cognitive ability level matches with typical development and chronological age matches with mixed-etiology intellectual disability.

METHODS AND PROCEDURES

Thirty-five participants with Down syndrome (11-21 years), 27 participants with intellectual disability (13-20 years), and 29 participants with typical development (4-6 years) completed a narrative story generation task. Transcripts were coded and analyzed for verb production.

OUTCOMES AND RESULTS

Examining overall verb production, participants with Down syndrome produced narratives with less verb density than participants with typical development and had smaller verb type-token ratios than participants with intellectual disability. Upon examining lexical verb production, participants with Down syndrome produced narratives with less lexical verb density than participants with typical development.

CONCLUSIONS AND IMPLICATIONS

The results indicate that individuals with Down syndrome have a developmentally appropriate diversity of verbs in their lexicon but are not using verbs as frequently as comparison groups.

The acquisition of different classes of words in Spanish children with Down syndrome

PURPOSE

The primary aim of this study was to analyze the acquisition of different classes of words in Spanish-speaking children with Down syndrome (DS), with special emphasis on nouns and verbs. A second objective was to compare the results obtained with those reported by Checa et al. (2016), who used a different measure to study vocabulary composition.

METHOD

We studied 108 children with DS and 108 children with typical development (TD), with mental ages between 9 and 29 months (DS M = 21;26 months;days, TD M = 20;23) and chronological ages between 8;24 and 68;19 months;days (mean = 41;11 and 20;19 for DS and TD, respectively). Children were matched individually for size of productive vocabulary and gender. Data were gathered using the MacArthur-Bates CDIs, adapted to the profile of children with DS (the CDI-Down). Relative proportions were used as the measure of vocabulary.

RESULTS

The results differed from those obtained by Checa et al. (2016) when using absolute proportions to examine vocabulary composition. The most significant difference was the trend among children with DS to produce fewer verbs and closed-class words (articles, prepositions, pronouns, conjunctions, and auxiliaries). There were no differences in the production of nouns and social words.

CONCLUSIONS

The tendency of children with DS to produce fewer verbs and closed-class words could be due to difficulties with morphology and syntax. This underlines the importance of morphosyntactic skills for learning these classes of words. The methodological and clinical implications of the results are discussed.