Exploring Expressive Vocabulary Variability in Two-Year-Olds: The Role of Working Memory Purpose This study explored whether measures of working memory ability contribute to the wide variation in 2-year-olds' expressive vocabulary skills. Method Seventy-nine children (aged 24–30 months) were assessed by using standardized tests of vocabulary and visual cognition, a processing speed measure, and behavioral measures of verbal working memory ... Research Article
Research Article  |   December 01, 2015
Exploring Expressive Vocabulary Variability in Two-Year-Olds: The Role of Working Memory
 
Author Affiliations & Notes
  • Jayne Newbury
    University of Canterbury, Christchurch, New Zealand
  • Thomas Klee
    University of Canterbury, Christchurch, New Zealand
  • Stephanie F. Stokes
    University of Canterbury, Christchurch, New Zealand
  • Catherine Moran
    University of Canterbury, Christchurch, New Zealand
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication. ×
  • Correspondence to Jayne Newbury: jayne.newbury@canterbury.ac.nz
  • Editor: Rhea Paul
    Editor: Rhea Paul×
  • Associate Editor: Lizbeth Finestack
    Associate Editor: Lizbeth Finestack×
Article Information
Development / Attention, Memory & Executive Functions / Language / Research Articles
Research Article   |   December 01, 2015
Exploring Expressive Vocabulary Variability in Two-Year-Olds: The Role of Working Memory
Journal of Speech, Language, and Hearing Research, December 2015, Vol. 58, 1761-1772. doi:10.1044/2015_JSLHR-L-15-0018
History: Received January 21, 2015 , Revised May 12, 2015 , Accepted July 31, 2015
 
Journal of Speech, Language, and Hearing Research, December 2015, Vol. 58, 1761-1772. doi:10.1044/2015_JSLHR-L-15-0018
History: Received January 21, 2015; Revised May 12, 2015; Accepted July 31, 2015

Purpose This study explored whether measures of working memory ability contribute to the wide variation in 2-year-olds' expressive vocabulary skills.

Method Seventy-nine children (aged 24–30 months) were assessed by using standardized tests of vocabulary and visual cognition, a processing speed measure, and behavioral measures of verbal working memory and phonological short-term memory.

Results Strong correlations were observed between phonological short-term memory, verbal working memory, and expressive vocabulary. Speed of spoken word recognition showed a moderate significant correlation with expressive vocabulary. In a multivariate regression model for expressive vocabulary, the most powerful predictor was a measure of phonological short-term memory (accounting for 66% unique variance), followed by verbal working memory (6%), sex (2%), and age (1%). Processing speed did not add significant unique variance.

Conclusions These findings confirm previous research positing a strong role for phonological short-term memory in early expressive vocabulary acquisition. They also extend previous research in two ways. First, a unique association between verbal working memory and expressive vocabulary in 2-year-olds was observed. Second, processing speed was not a unique predictor of variance in expressive vocabulary when included alongside measures of working memory.

Acknowledgments
This research was funded by a grant from the Marsden Fund, Royal Society of New Zealand (Grant uoc1003) and a doctoral scholarship awarded to the first author from the University of Canterbury, New Zealand. We thank our research assistants and technical advisors. Thanks also to our local health and education providers who helped with recruiting participants. Most of all, thanks to the families and children who made this study possible.
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