A big one is institutional pressure. A child’s time spent with a second language is time not spent on their first. So teachers often discourage parents from speaking their languages to their children. (This is especially true if the second language lacks prestige.) Parents often reluctantly comply, worried about their offspring’s education. This is a shame; children really can master two languages or even more. Research does indeed suggest their vocabulary in each language may be somewhat smaller for a while. But other studies hint at cognitive advantages among bilinguals. They may be more adept at complex tasks, better at maintaining attention, and (at the other end of life) suffer the onset of dementia later.
一个大因素就是制度性压力。如果一个孩子的时间花在第二语言上那么讲母语的时间就肯定少了。所以教师总是不鼓励父母和孩子讲自己的母语。（这种情况尤其体现在第二语言没那么普及的时候。）考虑到孩子的教育，父母往往会不情愿地遵从。这确实很可惜；孩子们实际可以掌握两种或更多语言。研究确实表明，一段时间内，每种语言的词汇量会减少。但其他的研究也暗示了双语习得者的认知优势。可能更擅长复杂的任务，更善于保持注意力，（在老年时）更晚得痴呆症。
Even without those side-effects, though, a bilingual child’s connection to relatives and another culture is a good thing in itself. How to bring it about? When both parents share the heritage language, the strategy is often to speak that at home, and the national language outside. But when they have different languages, perhaps the most common approach is “one parent, one language”. François Grosjean, a linguist at the University of Neuchâtel in Switzerland, emphasises necessity. He recommends reserving occasions on which the only language that may be spoken is the one that needs support.
即使没有这些附加优势，掌握双语的儿童和亲人以及另一种文化的连接本身就是一件好事。如何实现？父母双方都使用传承语言，可以采用在家讲传承语在外面讲本国语言的策略。但若父母双方讲不同语言，也许最常见的方法是“和父母各讲一种语言”。瑞士纳沙泰尔大学语言学家弗朗索瓦·格罗让强调了家族内传承语言的重要性。他认为讲一种语言的唯一保留场合正需要支持。
Sabine Little, a German linguist at the University of Sheffield, puts the emphasis elsewhere. Making the heritage language yet another task imposed by parents can lead to rejection, she argues. She recommends letting the child forge their own emotional connection to the language. Her son gave up on German for several years before returning to it. She let him determine when they would speak it together. (He decided on the pair’s trips in her car to after-school activities, during which his father, who doesn’t speak German, would not be excluded.) They joke about his Anglo-German mash-ups and incorporate them into their lexicon. Like many youngsters, his time on YouTube is restricted—but he is allowed more if he watches in German. Ms Little suggests learning through apps and entertainment made for native speakers; the educational type smack of homework, she thinks.
谢菲尔德大学德国语言学家扎比内·利特尔则把重点放在其他地方。她认为让传承语言成为父母强加给孩子又一项任务可能会让孩子反感。她建议让孩子们自己建立和语言的情感联系。她儿子好几年不学德语，后来又重学的。他让孩子决定什么时候一起说德语。（孩子决定坐上她的车参加亲子课外活动，在此期间孩子不会说德语的父亲也不会排除在外。）他们拿他的英德混搭开玩笑，并将其纳入他们的词典。和许多年轻人一样，孩子上YouTube的时间受限——但如果用德语观看就可以看更长时间。利特尔建议通过专为母语人士设计的应用程序和娱乐学习；她认为这种教育类型有点像家庭作业。
Languages are an intimate part of identity; it is wrenching to try and fail to pass them on to a child. Success may be a question of remembering that they are not just another thing to be drilled into a young mind, but a matter of the heart.
语言是身份的重要组成部分；试图将其传递给后代却失败是痛苦的。要想成功得记住语言不仅要灌输到下一代的脑子，还要到达心灵。

来源：经济学人