title: Exploring Expressive Vocabulary Variability in Two-Year-Olds: The Role of Working Memory.
abstract: OBJECTIVE
  This study explored whether measures of working memory ability contribute to the wide variation in 2-year-olds' expressive vocabulary skills.
  
  
  METHODS
  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.
authors.forename: Jayne
authors.initials: J
authors.lastname: Newbury
authors.forename: Thomas
authors.initials: T
authors.lastname: Klee
authors.forename: Stephanie F
authors.initials: SF
authors.lastname: Stokes
authors.forename: Catherine
authors.initials: C
authors.lastname: Moran
mesh_terms: D000367:Age Factors; D002663:Child Language; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007807:Language Tests; D008297:Male; D008570:Memory, Short-Term; D015999:Multivariate Analysis; D010700:Phonetics; D012727:Sex Characteristics; D013067:Speech Perception; D013997:Time Factors; D014825:Vocabulary