Modeling Vocabulary Growth in Autistic and Non-Autistic Children

Document Type

Article

Publication Date

2024

Abstract

Background: Autistic children are typically late to develop their expressive vocabulary, but little is known about their early word learning process. This study compared three network growth models on their ability to account for the trajectories of expressive vocabulary acquisition in autistic and non-autistic children.

Methods: We studied expressive vocabularies using item-level data from a child vocabulary checklist (n = 721 records from young autistic children; n = 2,166 records from non-autistic toddlers). We estimated vocabulary growth trajectories for autistic and non-autistic children and assessed the goodness of fit of three models of vocabulary growth, with varying sensitivity to the structure of the environment and the learner's existing vocabulary knowledge. To do so, we first computed word-level acquisition norms that indicate the vocabulary size at which individual words tend to be learned by each group. Then we evaluated how well network growth models, based on natural language co-occurrence structure and word associations, accounted for variance in the autistic and non-autistic acquisition norms.

Results: Our word-level vocabulary size of acquisition norms closely aligned with age of acquisition data, indicating their utility when age of acquisition norms cannot be derived for neurodivergent populations. Furthermore, we extended key observations and demonstrated that the growth models explained similar amounts of variance in each group. Both groups are biased to learn words that have many connections to words that have been previously learned; however, even after accounting for this learning influence, autistic and non-autistic vocabulary growth trajectories receive an added boost in learning when words are connected to many other words in the learning environment, indicating a similar learning profile.

Conclusions: Both groups preferentially acquire new words by leveraging the semantic structure in the learning environment, indicating an overlap in theoretical accounts of vocabulary growth.

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