Dissertations, Theses, and Capstone Projects

Date of Degree

6-2017

Document Type

Dissertation

Degree Name

Ph.D.

Program

Psychology

Advisor

Patricia J. Brooks

Committee Members

Kristen Gillespie-Lynch

Lana Karasik

Anna Stetsenko

David Rindskopf

Subject Categories

Developmental Psychology

Keywords

motor coordination, sequence learning, language development, individual differences

Abstract

Dual-route approaches to language acquisition posit separable mechanisms for acquisition of vocabulary and grammar (e.g., Pinker, 1998). Working within the dualistic framework, Ullman and Pierpont (2005) proposed the procedural deficit hypothesis, which proposes that impairments in rule-based aspects of language (e.g. grammar, phonology) observed in children with Specific Language Impairment (SLI) may be linked to neural deficits that govern procedural memory and are critical for the procedural/sequence learning of both, cognitive and motor skills. In support of this hypothesis, recent meta-analyses indicate significant deficits in sequence learning in children with SLI relative to controls (Lum et al., 2014). Further research has found deficits in nonword repetition among children who are language impaired. Nonword repetition has also been associated with children's vocabulary development (Gathercole & Baddeley, 1990) suggesting that while nonword repetition is hypothesized to be procedural in nature, it is highly associated with children's word learning, which is thought to be learned declaratively.

In contrast to the dual-route framework, which has received more attention in the more recent years, single-route approaches to language development view vocabulary and grammar learning as fundamentally interconnected, as supported by very high correlations between measures of vocabulary diversity and grammatical complexity (e.g., mean utterance length) at all stages of development. This idea that all aspects of language are interrelated emerges from domain-general theories of child development and extends beyond language by suggesting that links exist between children’s language, motor, and cognitive development (Bates & Dick, 2000; Iverson & Thelen, 1999). This approach is supported by neurodevelopmental research (Diamond, 2000), in addition to research showing that children with language impairments also show difficulties in motor control. In line with this view, researchers have been pushing for a unification between the fields of motor and language development (Iverson, 2010).

The majority of the literature that has found support for the dual-route hypothesis has used extreme-group design to examine differences between clinical and typically developing populations. In this study, we use an individual differences approach to examine the role of sequence learning and motor coordination (fine motor coordination in particular) in language development in a community sample of school ages children. We administered a battery of language and cognitive assessments to a diverse community sample of 63 children (33 girls, 30 boys), mean age 8 years; 2 months (SD 1;3). We employed a commonly used measure of sequence learning (the Serial Reaction Time task) in addition to the pegboard task to examine motor coordination and the nonword repetition task to examine phonology. Results showed that while controlling for age and nonverbal working memory, using the traditional measures of sequence learning, we were unable to find a relationship with any measure of language, this finding was in line with some of the individual differences research in the field (Lum & Kidd, 2012) but not with group-level research looking at sequence learning between SLI and typically developing children. On the other hand, measures of motor coordination (as measured using the pegboard task) were related to individual differences in all aspects of language, including vocabulary, grammar, and phonology. Furthermore, all language measures were correlated with one another. In attempts to replicate these findings, we found associations between motor coordination (measured using accuracy on Block 1 of the SRT task) and measures of vocabulary and grammar. Post-hoc analyses also showed that nonverbal intelligence was also associated with performance on the pegboard task. These results implicate fine motor coordination as a factor contributing to variance in language and cognitive abilities, but fail to support the view that word-based (vocabulary) and rule-based (grammar and phonology) aspects of language are different and possibly acquired via separable mechanisms. Our findings are in line with domain-general approaches to development which discuss the relationships between both verbal and motor abilities in children, suggesting that these two developmental areas are largely intertwined (Thelen, 2010).

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