A Longitudinal Analysis of Vocabulary Structure in Persistent Late-Talkers, Late-Bloomers, and Typically-Developing Toddlers

• In Event: Poster Session 07
  In Poster Session: PS 07 Topic - Language, Communication

Abstract

There is enormous early variability in vocabulary size for toddlers in their second year of life, making it hard to determine who is in the range of typical word learning, and who will continue to have persistent language delays (Rescorla, 2011). The key question has become, “who will show typical language development, who is at risk for these adverse outcomes, and who will show some delay but “catch up” to their typical peers by school-age?” Though total vocabulary size can be one indicator, understanding early differences in vocabulary structure, or the kinds of words toddlers know, may be the key to answering the above question (MacRoy et al., 2016; Rescorla & Arunachalam, 2019).
In the present study we analyze the size and proportions of different word categories in three talker groups over a year-long longitudinal study, with 84 children starting the study at 17.67 months of age (SD = 0.96). Parents filled out the MacArthur-Bates Communicative Development Inventory monthly, which yielded five categories: nouns, verbs, adjectives, grammar function words, and other words (e.g. routine words such as “bye bye”). Using their scores on the CDI, we divided our participants into persistent late talkers (PL, < 20th% at Visit 1 & 12), late bloomers (LB, <20th% at Visit 1, > 20th% at Visit 12), and typically developing children (TD, >20th% at Visit 1 & 12). All pairwise comparisons were adjusted using bonferroni corrections.
At visit 1, differences emerge between LB and TD children in the proportion of their vocabularies composed of verbs and other words (Table 1). Interestingly, LB and PL children only differed in their initial proportion of adjectives, suggesting a possible avenue for future investigation. However, by the end of the study, PL children significantly differed from their LB and TD peers in every category. PL children tend to show more variability in their vocabulary trajectories. Further, PL children show delayed trajectories in every category. However, category analyses suggest that 1) looking at overall vocabulary, which is invariably made up of mostly nouns, may not be the best strategy for identification, and 2) PL children start out with their vocabularies containing higher percentages of other words, and continue to have much larger proportions of these words over time. This second result, along with the large heterogeneity among late talkers, suggests that these populations may differ in how they accrue language. For instance, these results are in line with past work suggesting that this group of children learns more unrelated words, building weak semantic networks that hinder further vocabulary learning (Beckage et al., 2011; Kim & Yim, 2018).
Overall results suggest that analyzing the structure of young toddlers’ vocabularies may help differentiate these groups for early identification, perhaps in combination with other screening tools. Further, this method may elucidate underlying language learning mechanisms of different talker types. Future studies could investigate how to utilize knowledge of vocabulary structure to aid intervention efforts.

Authors

• Jennifer Weber, University of Colorado Boulder
  Presenting Author

• Eliana Colunga, University of Colorado Boulder
  Non-Presenting Author