Framework for Linking Phonological and Morpho-syntactic Sequential Pattern Rules in Developmental Language Diorders
Funding: NIH, National Institute on Deafness and Other Communication Disorders
A hallmark of English-learning children with developmental language disorder (DLD) is the inconsistent production of grammatical morphology. However, recent work also implicates the phonological domain, as indicated by deficits in nonword repetition and in producing novel word forms. The hypothesis driving the current project is that morphological and phonological deficits are causally linked by a broader deficit in sequential pattern learning. We take a developmental approach, combining what we already know about morphosyntactic deficits in DLD with recent developments in the fields of linguistics and language acquisition. First, it is possible to divide phonological and morphological patterns into three pattern types (Single Feature, OR/Disjunction, Family Resemblance/Prototype), with these types having a long history of study in visual pattern learning. Importantly, children with DLD appear to have maximum difficulty with morpho-syntactic patterns of the OR type (e.g., regular past tense). In contrast, studies using artificial grammars show that infants who are typically developing are highly adept at learning Single Feature and OR pattern types; Family Resemblance patterns may be weaker. Typical adults are adept at Single Feature and Family Resemblance patterns, but appear to be, at least superficially, more like children with DLD in their performance on the disjunctive OR pattern.
The proposed research links deficits in phonological and morphological sequence learning in children with DLD. We also ask if dependence on the associatively organized lexicon can account for the infant-to-adult developmental changes observed for the OR pattern (which is not associatively organized) and thereby explores the possibility that children with DLD rely on their lexicons to compensate for their sequential pattern learning deficit. The results of the proposed studies promise to help identify the underlying mechanism(s) of DLD and to suggest possible intervention strategies, such as employing semantic cues and strengthening lexical organization.
