Function Words Production and Williams Syndrome in Catalan and Spanish

This study examines the use of function words in adult individuals with Williams syndrome (WS) compared to typically developing (TD) speakers, focusing on spontaneous speech in Catalan and Spanish. The aim is to assess both quantitative and qualitative aspects of function word production and to explore whether WS is associated with distinct grammatical processing patterns. The corpus consisted of 20 five-minute transcripts, equally divided by language (Catalan/Spanish) and group (WS/TD). Analyses included counts of function word categories, error types, and mean length of utterance in morphemes (MLUm). Statistical procedures (t-tests, ANOVA, Mann–Whitney tests, and MANOVA with bootstrapping) were applied depending on distributional assumptions. Results showed significant differences between WS and TD groups in several categories, including prepositions, conjunctions, definite articles, numerals, adverbs, and relative pronouns, with large effect sizes in some cases. MLUm was also significantly lower in the WS group. In contrast, no significant effects of language or interaction between language and group were found. These findings indicate that WS has a robust impact on grammatical usage, particularly affecting function words, independently of language. On the whole, the results support the view that WS is associated with atypical linguistic profiles and contribute cross-linguistic evidence from Romance languages, highlighting the need for further research on language processing in this population.