Learning A New Language May Make You Forget Your Old One

...but only temporarily. It actually makes a lot of sense when you think about it:

naming objects in another language inhibits the corresponding labels in the native language, making them more difficult to retrieve later. Interestingly, the study also showed that the more fluent bilingual students were far less prone to experience these inhibitory effects. These findings suggest that native language inhibition plays a crucial role during the initial stages of second language learning. That is, when first learning a new language, we have to actively ignore our easily accessible native language words while struggling to express our thoughts in a novel tongue. As a speaker achieves bilingual fluency, native-language inhibition becomes less necessary, accounting for the better performances of fluent bilingual speakers in the study.

It certainly chimes with my experience. I guess too that it shows up the necessity of helping people to consolidate new vocabulary in other kinds of learning too.

ScienceDaily: A New Language Barrier: Why Learning A New Language May Make You Forget Your Old One: Filed in: language, acquisition, learning, psychology