Atypical Language Development
Blog post: Based on the introduction to the JCL’s Special Issue on Atypical Language Development
Written by Letitia R. Naigles and Edith L. Bavin
The Journal of Child Language’s recent special issue on atypical language development includes 11 excellent papers on a range of disorders (Down syndrome (DS), Williams syndrome (WS), Fragile X syndrome (FXS), dyslexia, Autism Spectrum Disorders (ASD), Specific Language Impairment (SLI), Pre/perinatal brain injury (BI)) manifested by children learning a range of languages (English, British Sign Language (BSL), Dutch, German, Hebrew, Kuwaiti Arabic).
To the extent that child language acquisition relies on the neural substrate of the brain, then children with specific kinds of atypical neural substrates should show atypical processes and/or products of language development. Investigations of atypical language development in children, can help reveal which underlying (nonlinguistic) components are required and what they are required for, which processes are resilient or robust, and the degree to which language representations break down in graded or absolute fashion within a given disorder.
Papers in this issue provide compelling evidence that grammar is impaired in both toddlers and school age children with DS or WS (both of whom display lower general cognitive functioning) compared with children with FXS or typical development (TD). Yet a phonological system is clearly available to children with DS even when their articulation is problematic. In other papers, the extent to which social abilities contribute to acquisition is investigated with children with ASD, who show marked restrictions in social interaction, and WS, who are highly social. The research reported shows that removing social engagement from the toolkit of children with ASD impacts on their word learning; however, the presence of social engagement in children with WS does not guarantee intact language development, neither within the pragmatics realm nor with respect to the timing of grammatical development.
Some aspects of language development seem to proceed typically in children with disorders: In the lexical domain, the content and organization of vocabularies encompassing the first 50 words were strikingly similar for children with ASD’s and children with TD; and for children acquiring BSL (TD and those with SLI), semantic clustering effects were found. In the grammatical realm, similarly to children with TD, children with BI produced gesture-speech combinations encompassing simple propositions several months before they produced those propositions entirely in speech; additionally, children with WS and DS learning Hebrew produced many grammatical elements in the same developmental order (i.e., synchronously) as children with TD, suggesting that these elements cohered as a system for these groups. But not all early language development processes show resilience: the research reported showed no evidence of learning non-adjacent dependencies in an artificial language for toddlers at familial risk for dyslexia and, hence, no evidence for sensitivity to regularities when processing such utterances. These findings suggest that language development that appears to be typical at specific points in time may be proceeding via different underlying routes/processes.
For a given disorder and/or across disorders systematic graded or partial impairments may be observed within a given area or subarea of language. Evidence of rule use in German- or Arabic-speaking preschoolers with SLI is reported: Children inflected novel verb or noun stimuli appropriately and produced overgeneralizations at levels comparable to children with TD matched on language-level. However, performance by children with SLI was consistently poorer. Such findings pose a theoretical challenge: how can a given area of language appear to be rule-governed to some extent but not in total?