Language Subdomains in Children on the Autism Spectrum: Cross-Sectional Study of Morphologically Rich Language

Children on the autism spectrum (AS) show considerable individual differences in language development. It remains unclear whether their lexical and grammatical skills develop in a typical pattern, with or without delays in both domains, or whether they exhibit an atypical language profile in which lexical and grammatical development are differentially affected. Since most existing studies involve English-speaking children, the relationship between these language domains in morphologically rich languages such as Croatian remains underexplored. In morphologically rich languages, grammatical meaning is predominantly encoded morphologically, resulting in high variability of word forms. The aim of this study was to examine the relationship between lexical and grammatical (morphological and syntactic) skills in Croatian-speaking children on the AS and to determine whether they display a typical or atypical language profile.

The study employed a cross-sectional design. The sample consisted of 30 children on the AS and 30 vocabulary-matched typically developing (TD) two-year-old children. Lexical, morphological, and syntactic abilities were assessed using parent reports, and data were analyzed both within and between the groups.

Significant positive correlations were found between vocabulary and grammatical measures in both groups, with no significant differences in grammatical abilities between vocabulary-matched AS and TD children. Although both groups demonstrated more advanced lexical than morphological abilities, this pattern reflects typical Croatian language acquisition rather than a characteristic specific to AS.

The findings support the hypothesis of a typical, though often delayed, language profile in children on the AS, in which grammatical development follows lexical growth. The grammatical development of children on the AS acquiring a morphologically rich language did not differ from that of younger vocabulary-matched TD peers. These results underscore the importance of assessing and targeting both vocabulary and grammar in parallel during early intervention for children on the AS.