Word-Learning Biases Contribute Differently to Late-Talker and Typically Developing Vocabulary Trajectories

AbstractThis study explores how the vocabulary growth trajectories of typically developing and late-talker children change in relation to their word learning biases. Thirty-nine late talkers and 45 typically developing toddlers visited the lab once a month for one year starting at about 18 months of age. Word-learning trajectories were tracked using a parent-reported vocabulary measure, and shape and material bias measures were collected using the novel noun generalization task each month. A two-level hierarchical linear model was utilized for the longitudinal analyses. Results indicate that, at the first visit, a stronger shape bias was significantly associated with a larger vocabulary in typically developing talkers. In late talkers, however, a stronger initial shape bias was associated with a smaller vocabulary. Over the course of the study, for every additional visit, stronger shape biases were associated with larger vocabularies in late talkers, but not in typically developing toddlers. Results for the material bias mirrored the shape bias results. These findings suggest different possible underlying mechanisms for the two groups of children, as well as avenues for the design of language interventions that might support young late talkers.

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