Current Research Projects

A Developmental Framework for Linking Phonological and Morpho-syntactic Sequential Pattern Rules In Developmental Language Disorder

Principal Investigators: Lisa Goffman and LouAnn Gerken (University of Arizona)
Funding: NIH, National Institute on Deafness and Other Communication Disorders

A hallmark of English-learning children with developmental language disorder (DLD, AKA specific language impairment) is the inconsistent production of grammatical morphology. However, recent work also implicates the phonological domain, as indicated by deficits in producing word and nonword forms. The hypothesis driving the current proposal is that morphological and phonological deficits are causally linked by a broader deficit in sequential pattern learning. The unique approach taken here combines what we already know about morpho-syntactic 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 OR pattern.

With these intriguing findings as a starting point, the proposed research links phonological and morphological sequence learning in children with DLD. In Aim 1, we ask if 4- to 6-year-olds (typically developing (TD), DLD alone, DLD + speech sound disorder (SSD), and SSD with no morpho-syntactic deficit) and adults are sensitive to input examples that fit one of these three patterns. We predict that, consistent with their long-documented morpho-syntactic deficit, children with DLD will have particular difficulty with the phonological OR pattern. Consistent with their intact morpho-syntactic skills, children with SSD should show no deficits in the OR pattern, revealing a link between OR pattern learning, phonology, and morpho-syntax. Aim 2 explores whether the inclusion of a semantic subcategory cue facilitates learning the OR pattern. Aim 3 asks 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 to the OR pattern and strengthening lexical organization.

Sequential Pattern Learning in Children with Developmental Language Disorder

Principal Investigator: Lisa Goffman
Funding: NIH, National Institute on Deafness and Other Communication Disorders

Developmental language disorder (DLD; aka specific language impairment) affects approximately 7% of children at the time they enter kindergarten, with longstanding adverse academic, social, and communicative consequences. While there is no question that language deficits feature prominently in children diagnosed with DLD, there are other cognitive and motor capacities affected—such as pattern induction, rhythmic grouping, and sequential organization. Previous findings show that the capacity for deploying sequentially patterned information mediates language and motor production. Sequential patterning is a central component of phonology and morphosyntax–domains of language difficulty presented in children with DLD. It has become apparent that this broad profile of deficits cannot be explained by a general motor co-morbidity, but rather forms a core component of DLD. Therefore, it is crucial to determine whether learning and generalization would be facilitated by the inclusion of these more basic cognitive operations. Indeed, an exclusive focus on language (especially morphosyntactic) factors in intervention has resulted in slow and laborious learning in children with DLD with only small gains observed.

The central aim of this new 5-year project is to implement a novel framework for applying domain general cognitive mechanisms to learning and generalization; specifically all of the proposed experiments have in common the hypothesis that children with DLD will learn more effectively and generalize more broadly when targets are selected to emphasize the regularity of sequential patterns. The outcome of this work has the potential to inform early identification of very young children–when sequence learning (but not grammatical) deficits may be identified–and to alter the substance of intervention to incorporate broad cognitive, language, and motor mechanisms that underlie DLD.