How multi-lingual children learn languages

Same thing here: I learned some Spanish in high school, then studied Mandarin later. Now whenever I try to say things in Spanish, Mandarin comes out. It's like it took over the "foreign language" spot in my brain.

I was never really fluent in either of them, though, just barely proficient. I wonder if I had gotten to a higher level in Spanish, would it have been harder to unseat.

I've always thought this subject was very interesting as when I was younger I lived in Germany and German was actually one of my first languages, I used it in school as well as with friends. However when we came back to the US there was simply no opportunity to use it so I have lost most of it. Same goes for Spanish that I used to use semi-regularly when I was in my teens.

Naturally when I joined college I started studying language classes, Japanese the first year and every year after, as well as concurrently learning Chinese starting the second, I also went to college in Japan for a year focused on upper level Japanese. The process was me religiously studying, watching tv shows, constantly writing essays on my thoughts about society, culture, news, Rubik's Cubes, artificial intelligence, etc. even blog daily. Also listen to music. I can't emphasize enough how much I'd write and from the beginning engage daily in only using Japanese and Chinese in conversation. It took a year and a half to be conversational in Japanese (largely due to the completely different grammar and kanji) and for Chinese only around a year. I have also recently started Korean, to find that the overlap of Chinese and Japanese make it almost trivial to learn. So language similarity is also important.

Also in my years of interacting with foreigners who are learning English. The best speakers are typically ones who came here younger, there is even a large difference to students who studied abroad as early as high school (versus college)

I can definitely contest that you can still learn a language to very technical competency as late as in college. It just takes a lot of effort and discipline, and perhaps a bit of accumulated skill. Finally, you certainly get better at learning languages with every new language as with learning any subject.

I suggest reading the review article "Bilingualism and the brain: myth and reality" published in Neurologia in 2010: http://www.elsevier.es/en/abstract/revistas/neurologia-295/b...

I know what you mean about Spanish. I've never really studied it, unless you count a few weeks of introduction in high school and a bit of exposure due to living in the Phoenix area, but thanks to its Latin base and knowing French, I can read it somewhat reliably by guessing that words that look like French words have similar meanings. I can even pronounce it reasonably well according to some Spanish-speaking coworkers because the phonics of other languages have always automagically "clicked" for me, except when I have to learn new vowels or consonants.