The development of vocabulary, working memory and phonological awareness among Kuwaiti Arabic individuals with Down syndrome and typically developing children

Abstract

A large body of research has focused on language development throughout childhood among typically developing (TD) children due to its importance for communication, expressing feelings and needs, and maintaining relationships. Most research on language development within the context of intellectual disability, such as Down syndrome (DS), has been conducted among English speakers. However, there is a lack of research examining how trajectories among Arabic-speaking DS individuals might differ. This study employed a cross-sectional developmental trajectory approach to investigate vocabulary, phonological short-term memory and phonological awareness (PA) in relation to non-verbal mental ability as measured by Ravens Coloured Progressive Matrices (RCPM) raw scores in Gulf Arabic (Kuwaiti) DS and TD groups. It also addressed the relationships between phonological awareness and vocabulary knowledge (related to the lexical restructuring [LR] model), as well as theorized relationships between phonological short-term memory and vocabulary, and phonological short-term memory and phonological awareness. Forty-eight individuals with DS aged 6–20 years old were matched on RCPM with 44 TD children aged 3–10 years old. Data were collected for each participant in two sessions, assessing phonological short-term memory using a non-word recognition (NWR) test, testing receptive and expressive vocabulary, and assessing phonological awareness at the level of syllable, rhyme and phoneme. The findings show a similar onset and rate of development in PA and vocabulary across nonverbal mental ability for the DS and TD groups, but not in phonological short-term memory. In addition, there is a strong correlation between non-verbal mental ability (NVMA) and these skills in the DS group, but not with phonological short-term memory. Significant correlations between NVMA and some language skills would be predicted by neuro-constructivist theory, while further findings showing an association between vocabulary and phonological awareness to a similar extent across the DS and TD groups are in line with the LR model. Another important finding is that phonological short-term memory is associated with phonological awareness in different ways in the DS and TD groups. Moreover, phonological short-term memory is not significantly correlated with non-verbal mental ability or vocabulary measures in the DS group, implying that NWR plays no part in vocabulary development for individuals with DS. In contrast, there is a strong correlation between phonological short-term memory and vocabulary in the TD group, consistent with the phonological short-term memory theory. The

educational, clinical and policy implications discussed highlight the need for further study in this area, as well as for standardized Arabic tests.