Down syndrome, a genetic neurodevelopmental disorder, is caused by a chromosomal abnormality and is accompanied by mild to severe intellectual disabilities. From the beginning of people with Down Syndrome's lives, they face learning difficulties, mainly in the areas of grammar, articulation, and syntax with a delay in both non-verbal and verbal communication. Developmental language disorder, the causes of which have not yet been elucidated, consists of the failure to develop language and age-expected language skills in an otherwise typically developing individual. It is noticed in the early developmental period of the person and affects, as in Down syndrome, the quality of life of the person as a whole, as one or more language areas are affected. The purpose of this paper is to describe the language deficits of the above two disorders, to join the different levels of linguistic analysis, to describe the ways of manifestation and the criticality of the deficits, and to evaluate them in terms of their severity for the quality of life of these individuals.
TopIntroduction
Down syndrome (DS) and developmental language disorder (DLD) are two of the disorders that have repeatedly concerned the scientific community, with a lot of research being carried out to clarify the cognitive and linguistic profile of children with these characteristics. Down Syndrome is one of the best known and most frequently occurring syndromes (Katsarou & Andreou, 2019). It is caused by triplication of all or part of the 21st chromosome and affects 1/691 births (Loveall et al., 2016). Significant deficits are found in the development of the brain during the fetal age, which are responsible for the later low mental potential of children. These difficulties combined with the hearing deficits that children with this syndrome often face and various articulatory issues related to the morphology of their mouth, such as the large tongue, cause dysfunctions in communication and language development (Bird & Chapman, 2011).
Developmental language disorder (DLD) is a developmental disorder of unknown etiology characterized by slow pace and deficits in language development (Ricketts, 2011). These difficulties should not be due to cognitive, perceptual or neurological deficits, while there is a discrepancy between the low language level and the child's good index of non-verbal intelligence (Zarzo-Benlloch et al., 2017). Although initially considered a childhood disorder, research shows that it continues to affect individuals both in adolescence and into adulthood (Palikara et al., 2009). Children with DLD have difficulties in expressing speech and even in understanding. A chronological, psychomotor and graphomotor delay in the acquisition of language milestones and variations in the severity and duration of the problem are evident. Disorders of language development concern the field of morphosyntax but also the fields of phonology, vocabulary and pragmatics (Stavrakaki, 2006),
The aim of this chapter is to describe and compare the language development in DS and DLD both in terms of the areas of occurrence and the magnitude of the difficulties faced by these individuals in order to create a specific linguistic profile for these two groups. The characteristics of language development for the two groups are then recorded and compared per domain. The chapter examines the areas of: phonology, semantics, morphology, syntax, pragmatics, the production and reception of spoken and written language. At the end, the comparison between the language domains is made and conclusions are drawn for both language groups. The two groups were selected for comparison because of similarities in communication disorders involving communication difficulties and language disorders involving the structure rather than the use of language.
Down Syndrome
Language development in people with Down syndrome does not follow the same stages observed in typically developing children, according to the differential development hypothesis, implying that the differences observed between the two populations are the result of qualitative differentiation (Hodapp et al., 1995; Polisenska & Kapalkova, 2014). This hypothesis supports the existence of qualitative differences in language between people with Down syndrome and those who are typically developing.