Date on Senior Honors Thesis

5-2021

Document Type

Senior Honors Thesis

Degree Name

B.S.

Department

Psychological and Brain Sciences

Degree Program

College of Arts and Sciences

Author's Keywords

williams syndrome; early language development; maternal language; expressive vocabulary; lexical diversity; grammatical complexity

Abstract

For typically developing (TD) children, maternal language input (MLI) is an important contributor to early language development. Until now, possible relations between MLI and language development for children with Williams syndrome (WS), a genetic neurodevelopmental disorder associated with language delay and intellectual disability, have not been addressed. The aim of the present study was two-fold: to examine concurrent relations between MLI and child language abilities at 24 months and to determine if individual differences in MLI and children’s lexical and cognitive abilities at 24 months make significant unique contributions to the variance in child language abilities at 48 months for children with WS. Participants included 34 mother-child dyads. Lexical diversity (number of different words; NDW) and grammatical complexity (mean length of utterance in morphemes; MLUm) measures of MLI were assessed during a 30-minute naturalistic play session at 24 months of age. For the child, standardized assessments of language and cognitive ability, as well as lexical (NDW) and grammatical (MLUm) ability measures from the play session were collected at 24 and 48 months of age. Mothers also completed a parent-report measure of child lexical and grammatical abilities at both ages. Concurrent relations between MLI and child measures of language and cognitive development were significant for maternal NDW but not for maternal MLUm. Regression analyses indicated that maternal NDW contributed significant unique variance to child receptive language at 48 months, even after taking into account child 24-month expressive vocabulary and 24-month nonverbal reasoning ability. Maternal MLUm accounted for significant unique variance in child receptive language and child MLUm at 48 months, even after accounting for the contributions of child 24-month expressive vocabulary and nonverbal reasoning ability. Implications of these findings are discussed.

Lay Summary

Williams syndrome (WS) is a developmental disorder that is caused by the deletion of 26 genes on chromosome 7, which results in mild to moderate intellectual disability or learning difficulties. Most children with WS evidence language delay. For typically developing (TD) children, the language used by the mother when talking to them (referred to as maternal language input; MLI) affects the child’s early language development. Until now, there have not been any studies of the relations between MLI and the language abilities of children with WS. This study aimed to address this need. I considered two research questions:

(1) What are the concurrent relations between MLI and child language and cognitive abilities for 24-months-olds with WS?

(2) What aspects of MLI measured when the child was 24 months old significantly predict child language abilities when the child is 48 months of age?

Participants included 34 mother-child pairs. For this study, lexical diversity (defined as the number of different words produced; NDW) and grammatical complexity (defined as the average length of spoken utterances taking into account word endings such as plural -s or past tense -ed, measured by mean length of utterance in morphemes; MLUm) were collected for the mother at the 24-month visit during a 30-minute naturalistic play session with her child. NDW and MLUm were measured for the child at both the 24-month play session and the 48-month play session. The child’s language and cognitive abilities were measured using a standardized assessment at 24 and 48 months of age. Mothers also completed a parent-report measure of child lexical and grammatical abilities at both ages. Regarding the first research question, the correlational analysis at 24 months identified significant relations between maternal lexical diversity and all child language and intellectual measures, whereas maternal grammatical complexity was not significantly related to any of the child measures. To answer the second research question, multiple regression analyses were completed to identify significant MLI predictors from the 24-month play session to child language abilities at 48 months of age. Results indicated that more complex maternal grammar and greater lexical diversity predicted children’s 48-month receptive language ability even after taking into account the roles of children’s 24-month vocabulary size and 24-month nonverbal reasoning ability. Additionally, greater maternal grammatical complexity significantly predicted children’s 48-month grammatical ability, even after taking into account the contributions of children’s 24-month expressive vocabulary and nonverbal reasoning ability. Implications of these findings are discussed.

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