Expressive Vocabulary in Mandarin-Speaking Autistic, Developmentally Delayed, and Typically Developing Children: A Cross-sectional Study.

Purpose: Research investigating the characteristics of expressive vocabulary in children with autism spectrum disorder (ASD) is limited, particularly in cross-linguistic contexts. This study aimed to systematically identify the characteristics of expressive vocabulary in 3- to 6-year-old Mandarin-speaking children with ASD.

Methods: We analyzed 10-min spontaneous language samples from parent-child free play sessions involving 21 children with ASD, 18 developmentally matched children with developmental delay (DD), and 15 chronologically age-matched typically developing (TD) children. The analysis was based on the grammatical characteristics of Mandarin.

Results: All three groups demonstrated a preference for verbs. Children in the ASD group showed a significantly lower number of tokens and types than those in the TD group in 11 content word categories and five function word categories. The ASD group exhibited greater similarities with the DD group in most vocabulary categories regarding the number of tokens, types, and type-to-token ratio (TTR) but still displayed subtle differences. Notably, the ASD group had a significantly higher total TTR than the TD and DD groups. The number of types of common nouns, number of tokens of pronouns were significantly lower in the ASD group than in the DD group.

Conclusion: These preliminary findings suggest that the language development of TD children is reflected in standardized tests and vocabulary expression in spontaneous language samples compared to children with ASD. Additionally, the qualitative differences in expressive vocabulary between the DD and ASD groups indicate that children with ASD may exhibit atypical vocabulary learning mechanisms.