Research has shown that children learning English plus another language during the early years tend to have a slightly smaller English vocabulary around age 3 or 4, but there is certainly no harm to the child to learn two languages, and there’s a subsequent “catch-up” period. When the research takes into consideration the number of words known in the second language, the bilingual children are about up to par. In addition, some language specialists claim that exposure to two languages helps children become language-proficient in ways that are difficult to demonstrate. That is, learning that objects and events can have more than one name helps the child grasp more readily the fact that words assigned to these objects and events are arbitrary and are related to family and cultural experiences.
Many people consider concern about this issue to be a uniquely American problem. Children living in other countries pick up two or three languages with no ill effects, and certainly the experience makes them more receptive to serious non-native language learning. And now in America hundreds of thousands, if not millions, of children are learning English as a second language and thriving linguistically in the process. Furthermore, we are on the verge of requiring all children to acquire proficiency, not merely exposure, to Spanish in their elementary and secondary educational careers. So giving your child a boost in this regard should be helpful.
My advice to parents, since the research is not definitive, represents a commonsense approach. I would definitely continue two-language exposure but would choose a major language for the household and give it priority when talking to your daughter. And I wouldn’t worry about her private language just now. If it continues to be a major part of her output by the time she is 2½, I would seek out the help of a language specialist.
As a final comment, I feel I have to tell you where I stand on bilingualism. I consider it so important that I am studying Spanish now (I had two years in high school many years ago) and have enrolled in an intensive Spanish program in Mexico this fall. Everyone in North America needs to know how to speak and read Spanish. Good luck to you with your daughter.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.