Language properties matter: Evidence from vocabulary production in toddlers from low-income immigrant families in Italy with different heritage languages

Introduction. The vocabulary gap between bilingual and monolingual children and the relationship between heritage language (HL) and majority language (ML) in early vocabulary acquisition are still debated in the literature. One possible reason for the apparently contradictory findings in the literature is that the phonological similarity between the HL and ML varies from study to study. Cultural differences between different heritage language groups is another insufficiently examined factor. Different language combinations need to be investigated to understand children’s early bilingual vocabulary development across languages and cultures. This study examined the vocabulary production in two-year-old monolingual, Italian-speaking toddlers and bilingual toddlers from two linguistic communities of immigrant families in Italy coming from different cultures and with heritage languages that differed in their phonological overlap with Italian: Romanian and Nigerian English. Method. Participants were 61 toddlers from low-income families: 22 Italian-speaking monolingual children, 22 Romanian-Italian-speaking children, and 17 Nigerian English-speaking children. Heritage language and Italian-single, total and conceptual vocabulary sizes, vocabulary composition, and TEs were assessed using the Italian/HL version of the short form of the CDI. Results. The Italian vocabulary and conceptual vocabulary sizes of the bilingual children were significantly smaller than those of monolinguals. The Romanian-Italian-speaking children but not the Nigerian English-speaking children were comparable to monolinguals in total vocabulary. Both groups of bilingual children were higher in Italian vocabulary than in their heritage language. Romanian-Italian-speaking children produced higher proportions of TEs than Nigerian English-Italian-speaking children. Discussion. This study provides evidence from two specific language pairs rarely investigated in the literature. The results suggest that there is a gap between bilingual and monolingual toddlers in equivalent low-income conditions in early expressive vocabulary size in the majority-single vocabulary, but not in total vocabulary for the toddlers learning two phonological similar languages. The dominance of the majority language in both groups of young bilingual children from immigrant families indicates that we need to deepen our understanding of the role of educational and cultural contexts in multiple language acquisition. The phonological distance between the two languages should be considered in clinical and educational contexts to identify risk factors for language development.