Victor Mair has a fascinating post on this topic over at Language Log, with many interesting comments. He begins:
I'm sitting in the San Francisco International Airport waiting for my flight to Taipei. The guy next to me is happily chattering away on his cell phone to someone (or some people) at the other end of the "line". What is curious is that one moment he is speaking in Taiwanese, the next moment in Japanese, then English, and then Mandarin.I don't know whether it is proper to call this "code switching", because he is speaking each of these languages in whole sentences or even blocks of sentences.He does not speak the languages with equal fluency, but they all sound natural and do not require great effort on his part to produce. The man's first language seems to be Taiwanese, then comes Japanese (with a Chinese accent), English (with a multilingual accent), and Taiwan-style Mandarin.
What's going on? That is, who's on the other end of the conversation? Mair has a speculation of his own and others offer suggestions.
In the comments, for example, Gene Andersen:
As one who is incapable of being very good even at English, let alone anything else, it is always an experience to watch somebody like Lothar von Falkenhausen switch from perfectly polished English to French to German to Japanese to Chinese at a meeting without missing a beat. But the amazing linguists are the people from southern India–they grow up having to know English, Hindi and their usual language, and they generally wind up knowing all the Dravidian languages (which are close), and with that background they can learn anything. We had a Telugu-speaking temp for a while–she started chattering away in Bangali with a colleague from Bengal–I asked her if that was her fifth language or what, and she said "My tenth."
Michael c. Dunn:
I once knew a maitre d' in Cairo in the days when the Russians were still around. he was Armenian and grew up knowing Armenian, Russian, Arabic, and maybe Turkish, and had acquired excellent English and at least conversational French and German. That may not have been all. Also a couple I know: the husband grew up speaking English but knew Brazilian Portuguese, learned Persian in the Peace Corps and Arabic studying abroad, then married a Puerto Rican who was studying Italian literature. I've been at gatherings where there was extensive code-switching.
I worked with a guy who from the Netherlands at an American company. He spoke perfect American English with only the faintest trace of an accent. He lived in Barcelona and thus I assume he spoke Spanish though I never heard it myself. His wife is German and they spoke German in their home.I once met up with him at Schipol Airport to do some business nearby. He had to struggle for a minute to reset his brain to speak his native language!It's really sad that so many of us Americans are monolingual.