Symbolic functioning and language development in children with Down syndrome.

Background: Understanding the relationship between preverbal skills and language development has important implications for identifying communication delay/disorders and for early childhood intervention. In the case of children with Down syndrome, it is well established that symbolic play is associated with the emergence of language. However, the exact nature of this relationship remains unclear, as many previous studies have addressed functional play and not actual symbolic play, which is felt to have stronger links to language development. The design of studies has also meant that adults may have inadvertently modelled the targeted behaviours, in which case it is unclear whether the children truly comprehend the symbolic acts that they produce.

Aims: This study set out to investigate further symbolic functioning and language in children with Down syndrome by exploring truly symbolic play as opposed to functional play, as well as the understanding of a graded set of novel symbols. The aim was to find out whether the symbolic behaviours would be associated with each other and with language development or non-verbal cognition. It was hypothesized that symbolic functioning on a test of symbolic play and symbolic comprehension would be significantly correlated with each other and with language abilities as they all measure underlying skills in symbolic representation. It was hypothesized that symbolic skills and language would be less closely correlated with non-verbal abilities. Another goal was to study understanding of three types of symbols: gestures, miniatures and abstract symbols. It was hypothesized that gestures would be significantly easier to understand than miniatures or abstract symbols.

Methods & Procedures: Twenty-one children with Down syndrome aged between 32 and 95 months were assessed on the Test of Pretend Play and a novel symbolic comprehension task as well as on standardized language and non-verbal tests. Correlational analysis was carried out to determine the relationship between the various tests, and the children were divided into three age categories to examine how the relationship changed with development. Analysis was also carried out on the children's performance across the gesture, miniature and symbolic subtests of the symbolic comprehension task.

Outcomes & Results: When effects of chronological age were partialled out, symbolic play and symbolic comprehension were significantly correlated with each other and with expressive and receptive language, but not with non-verbal ability. The association between language and symbolic functioning was significantly stronger in the younger children, but these measures started to dissociate with increasing age and language development. The data support the proposition that language becomes more domain specific as a result of experience and development. The results from the symbolic comprehension experiment revealed that the children found gestures significantly easier to understand than miniatures or substitute objects used as abstract symbols to represent other objects.

Conclusions: The findings indicate that tests of symbolic functioning offer valuable contributions to assessment with implications for intervention in children with Down syndrome and to the understanding of disorders of language and communication.