How to maintain first and second language skills

In the comments to "Cantonese as a Second Language" (4/22/19), there's an interesting discussion going on about how to maintain and / or acquire competency in more than one language.  This post started out as a comment to that thread, but it soon grew too long, so I've separated it off here.

My son was born in Taiwan and spent the first two years of his life in Taipei in an all-Mandarin household with lots of members (father, mother, grandfather, grandmother, and two aunts), and plenty of other relatives in the Taipei area (more uncles, aunts, cousins, etc.) — all mainlanders.  They all spoke Mandarin with him.

We moved to America (Boston area) when TK was two years old, and the core of the family moved with us, so the Mandarin-speaking nucleus of the extended family was still intact.

For the next four years, most of the people we visited with and his closest playmates also all spoke Mandarin.  During that period, he continued to speak almost exclusively in Mandarin.

Many of TK's older Chinese relatives had thick Shandong accents, and the younger ones spoke Táiwān guóyǔ 台灣國語 (Taiwanese Mandarin), and there were also varying amounts of Sichuanese thrown in to the mix, because the family had spent about a decade in that province during WWII and picked up a fair amount of Sichuaneseisms there and in the communities they lived in after they moved to Taiwan toward the end of the 40s.

Despite all the topolectal influences swirling around him, my son spoke only perfect, exact Modern Standard Mandarin (MSM), because my wife spoke that to him, and I followed suit.  My son's MSM at age three was so good that he could correct his Grandma's pronunciation.  I shall never forget when she was telling him the story of "Snow White and the Seven Dwarfs", she pronounced the heroine's name with a Shandong accent so thick that you could cut it with a knife, something like "bei4shyueh3 gung1choo4", and little TK merrily and enthusiastically chirped with perfect MSM tones, vowels, and consonants:

"Bù, wàipó.  Bùshì 'Bei4shyueh3 gung1choo4'.  Shì 'Báixuě gōngzhǔ'."

"不,外婆,不是'Bei4shyueh3 gung1choo4'. 是'白雪公主'."

"No, grandma.  It's not 'Pansis Sney Wit', it's 'Princess Snow White'."

I could tell endless stories of this sort about TK's fantastic Mandarin at age two (here's one), and also about my mother-in-law's linguistic inventions and adventures trying to communicate in America when she had only a smattering of English (e.g., "Radcliffe" became  "Dawtaw Hawfo" — see if you can figure that one out).

TK's Mandarin from ages two to six was so good and so confident that my sister Heidi, when my wife and I were working at the Middlebury Summer School of Chinese in 1972, came to help us by babysitting TK and learned quite a bit of the language from him so that now, nearly half a century later, she can still say with exquisite pronunciation:

wǒ yào táng wǒ èle wǒ yào niàoniào māmā zài nǎ'er

我要糖 我餓了 我要尿尿 媽媽在哪兒

I want candy I'm hungry I have to peepee Where's Mom?

At age six, like most other children in America, TK went to elementary school, and then he learned English rapidly.  But his Mandarin to this day is still pretty good, because he had such a solid foundation, and we often were in situations, whether in America or in Taiwan or in China, where everybody was speaking Mandarin.

As for Chinese characters, we never forced TK to learn them, but he already recognized a few before we left Taiwan and he did acquire some literacy by attending weekend classes while he was in middle school.  When he was in his early 20s, TK spent a year in Hangzhou and learned to read and write with characters fairly well then.  We still have a precious scroll on which he wrote a long, loving poem to his Mother — all in Chinese, and illustrated with beautiful Chinese-style water colors.

I think that the lesson to be learned from my son's experience with Mandarin and Chinese characters may best be exemplified by one of my favorite Chinese expressions:  "Tīngqízìrán 聽其自然" ("Let nature follow its own course; let it be").  Never compel a child to learn a language or a script.  If it's meant to be, provide a nurturing environment, and just let it happen.