Benefits of Bilingualism
A number of studies have concluded that bilingualism improves cognitive development and ability regardless of which two languages are involved.
Ricciardelli, L. A. (1993). An investigation of the cognitive development of Italian-English bilinguals and Italian monolinguals from Rome. Journal of Multilingual and Multicultural Development, 14(4), 345-346. from Linguistics and Language Behavior Abstracts database.
For example, an Italian study of students who spoke both Italian and English determined that students who demonstrated high proficiency in both English & Italian achieved higher scores on the creativity, meta-linguistic awareness, and reading achievement tests.
Likewise, a French-Italian study of bilingual children fluent in both languages determined that bilingualism in early childhood exerts a positive effect on the formation of cognitive processes in children.