Bilingualism is the ability of an individual to speak two languages well. A study by Florida Atlantic University researchers found that two languages can develop simultaneously but independently in young bilingual children.

Their study was published in the journal "Developmental Science." The researchers found that each language proceeds to grow independently from another language when children learn them from birth. It grows at a rate that reflects the quality of the children's exposure to each language.

In a press release via EurekAlert, it was reported that the researchers conducted the study on Spanish- and English-speaking children. They discovered that the children's Spanish skills became vulnerable as children's English skills develop but not the other way around.

Their longitudinal data found evidence that the children's rates of Spanish growth declined as they developed stronger English skills. However, their Spanish skills did not cause their English-speaking growth to slow.

Erika Hoff, Ph.D., lead author of the study, said that, similar to monolingual developments, the size of bilingual children's vocabularies and the grammatical complexity of their speech are strongly related. She did clarify, though, that vocabulary and grammar in one language are not related to the same factors of the other language.

Holt and her collaborators David Giguere, a graduate research assistant at FAU and Jamie M. Quinn, a graduate research assistant at Florida State University used longitudinal data on bilingual children who were exposed to English and Spanish at birth. They measured the vocabulary and level of grammatical development in the participants in six-month intervals between the ages of two and a half to four years old.

It was noted that the researchers hypothesized that vocabulary and grammar development on the same timetable may be influenced by an internal factor to the child. They also explored the possibility that children may need specific vocabulary to start learning grammar and that vocabulary can provide the foundation for grammar.