Expressive-receptive gaps in lexical abilities have been documented for bilingual children, but few studies have investigated whether a similar gap is observed at the grammatical level. The current study assessed grammatical abilities through sentence production and comprehension tasks in both languages in 17 Basque-Spanish simultaneous bilingual 6- through 9-year-olds (both languages acquired before three years of age). The children scored lower in Basque than Spanish for sentence production, but no significant differences were found for sentence comprehension. While an expressive-receptive gap was found for both languages, this gap was larger in Basque than in Spanish. Object-verb agreement errors were especially prevalent in Basque production, possibly because verbs in Spanish only agree with the subject. These results demonstrate that expressive-receptive gaps are also observed in bilingual children’s grammatical abilities and may vary depending on the structural similarity between the two languages.

Expressive-receptive gaps in lexical abilities have been documented for bilingual children, but few studies have investigated whether a similar gap is observed at the grammatical level. The current study assessed grammatical abilities through sentence production and comprehension tasks in both languages in 17 Basque-Spanish simultaneous bilingual 6- through 9-year-olds (both languages acquired before three years of age). The children scored lower in Basque than Spanish for sentence production, but no significant differences were found for sentence comprehension. While an expressive-receptive gap was found for both languages, this gap was larger in Basque than in Spanish. Object-verb agreement errors were especially prevalent in Basque production, possibly because verbs in Spanish only agree with the subject. These results demonstrate that expressive-receptive gaps are also observed in bilingual children’s grammatical abilities and may vary depending on the structural similarity between the two languages.