Lexical development in bilingual infants and toddlers: Comparison to monolingual norms

This study compares lexical development in a sample of 25 simultaneous bilingual and 35 monolingual children for whom semilongitudinal data were collected between the ages of 8 and 30 months. A standardized parent report form, the MacArthur Communicative Development Inventory (1989), was used to assess the children\u27s receptive and productive vocabulary in English and/or Spanish. A methodology was devised to assess the degree of overlap between the bilingual children\u27s lexical knowledge in one language and their knowledge in the other. Using the measures presented here, there was no statistical basis for concluding that the bilingual children were slower to develop early vocabulary than was the monolingual group. The wide range of vocabulary sizes observed at these ages in normally developing children (Fenson et al. 1991) was observed in these bilingual children as well. The close correspondence of the pattern of the bilinguals\u27 growth in two languages at once to monolinguals\u27 growth in one suggests that norms for lexical development in bilinguals should be made with reference to the children\u27s performance in two languages together