英語學習「最佳年齡」假說，到底是真是假？To master a language, start learning it early. New evidence suggests a drop-off in results after the age of 17.學外語要趁早。新證據表明，人類在17歲之後語言學習效果將大幅下降。Those who want to learn a foreign language, or want their children to, often feel they are racing against the clock. People seem to get worse at languages as they age. Children often learn their first without any instruction, and can easily become multilingual with the right exposure. But the older people get, the harder it seems to be. Witness the rough edges on the grammar of many immigrants even after many years in their new countries.無論是自己想掌握一門外語，還是想讓孩子學好語言，人們往往感覺這是在跟時間賽跑。隨著年齡的增長，人的語言能力似乎在變差。兒童通常不需要指導就可以學好母語，而且在足量的學習之後，能很容易地掌握多門語言。而這一過程隨著年紀的增加似乎變得越來越困難。大量的移民抵達新國家多年後，語法依然非常生硬。Scientists mostly agree that children are better language learners, but do not know why. Some posit biological factors. Is it because young brains have an extreme kind of plasticity? Or, as Steven Pinker, a Harvard psychologist, argues, an instinct for language-learning specifically, which fades as the brain ages and (in evolutionary terms) is no longer needed? Others think children have special environments and incentives, not more conducive brains. They have a strong motivation to communicate with caregivers and imitate peers, and are not afraid of making mistakes in the way adults are.大部分科學家一致認為相對於成人，兒童是更佳的語言學習者，但是還沒找到原因。部分科學家由此提出了生物因素假說。是不是兒童的大腦具有極致的可塑性？抑或，如哈佛大學心理學家史蒂夫·平克所言，人類專門針對語言學習的本能，隨著大腦的老化而退化，逐漸不再被需要（按照進化論的說辭）？其他科學家則認為這一現象的原因在於兒童擁有特殊的環境和動機，並非大腦對於語言更加靈光。他們想要與照顧他們的人以及親密的同伴交流，因此具有強烈的動機，並且不像成人那樣害怕犯錯誤。Some believe any 「critical period」 may only apply to the sounds of a foreign tongue. Adults struggle with accents: eight decades after immigrating to America and four after serving as secretary of state, Henry Kissinger still sounds fresh off the boat from Fürth—in what is nevertheless elaborately accurate English. (An alternative explanation, runs a joke about Mr Kissinger, is that he never listens.)有些人認為，所謂「關鍵期」也許僅適用於外語的聲音系統。成人常常受困於口音：亨利·基辛格移民美國80年之久（期間還當了40年的國務卿），說話聽著還是像他從德國菲爾特剛到美國那會兒，雖然語言都很準確。（當然還有一個解釋，也就是關於基辛格的段子，說他從來不懂得傾聽。）But grammar is different, and some researchers have reckoned that adults, with their greater reasoning powers, are not really at a disadvantage relative to children. One study found that when adults and children are exposed to the same teaching materials for a new language for several months, the adults actually do better. Most such research has had to rely on small numbers of subjects, given the difficulty of recruiting them; it is hard to know how meaningful the results are.語法卻有所不同。有些研究者猜想成人並不比兒童有優勢，哪怕成人的推理能力更強。只有一項研究發現，讓成人和兒童通過相同的材料來學習一門新的語言，幾個月之後，成人的學習效果更好。由於招募困難，多數類似的研究樣本量很小，因此我們難以確定這些研究結果到底有多大意義。Now a large new study led by Joshua Hartshorne of Boston College (with Mr Pinker and Joshua Tenenbaum as co-authors) has buttressed the critical-period hypothesis. The study ingeniously recruited 670,000 online test-takers by framing the exercise as a quiz that would guess the participants』 native language or dialect. This made it a viral hit. The real point was to test English-learners』 knowledge of tricky bits of grammar, and to see how this correlates with the age at which their studies began.而現在一項大規模的新研究佐證了「關鍵期假說」，該研究由波士頓學院心理學助理教授喬舒亞·哈茨霍恩主導（平克教授和喬舒亞·哈茨霍恩作為共同合著者）。該研究把練習做成線上測試，用以推測參與者的母語或方言。這一作法引發了病毒式傳播，從而巧妙地招募了67萬參與者。而真正的目的是為了測試英語學習者對於語法難點的知識，從而揭示這與他們幾歲開始學語言的相關性。Do younger beginners do better because their earlier start gave them more learning time, or because they learned faster in early years? It can be hard to tease apart these two questions. But testing a huge amount of data against a number of possible learning curves allowed Mr Hartshorne to do precisely that. Many previous researchers had posited a drop-off at around puberty. The new study found it to be rather later, just after 17.起步早的學習者表現更好，是因為他們早開始，有更多的學習時間，還是由於他們在早期學得更快？要把這兩個問題分開很難。但通過把海量數據與若干可能的學習曲線進行對比，哈茨霍恩卻做到了這點。很多之前的研究者猜測學習效果大幅下降發生在青春期前後。而這項研究發現下滑要晚得多，正好在17歲之後。Despite that later cut-off, learners must begin at around ten if they are to get to near-native fluency. If they start at, say, 14, they cannot accumulate enough expertise in the critical period. Unfortunately, 14 or so is precisely when many students, especially in America, are first introduced to a new language. (Even worse, this is an age when children are acutely sensitive to embarrassment in front of peers.)儘管下滑要晚得多，如果要達到近乎母語的流利度，學習者就必須在10歲左右開始學習。假如他們是在14歲才起步，那麼就無法在關鍵期內積累足夠的練習。不幸的是，14歲左右，正是很多學生，尤其美國學生，剛開始被要求修習一門新語言的年齡。（更糟的是，這個年紀的孩子特別害怕在同伴面前出醜。）Children who start at five don’t do noticeably better than those who start at ten over their lifetimes. But there is still reason to begin in the first years of school, as in Denmark and Sweden. Because mastery takes a long time—perhaps 30 years until improvement ceases—those who begin at five and are obliged to read and write English at university will by then have made much more progress than those who took the plunge at ten, even if their level is roughly the same by 40.整體來看，與10歲開始的學習者相比，5歲起步的學習者取得的成果並沒有明顯的差別。但是我們仍有理由相信最好從上學第一年就開始，像丹麥和瑞典一樣。因為熟練掌握語言所需的時間很長——也許要30年才會停止進步——那些5歲起步的學習者，如果在大學期間需要用英語閱讀和寫作，那時他們在之前累積的進步比那些10歲才開始的學習者要多得多，哪怕他們的語言水平在40歲時相差無幾。The existence of the critical period is not a reason for anyone 11 or older to give up. Some people remain excellent language students into adulthood. And Mr Hartshorne tested some truly subtle features of grammar that take years to master. A language learned even to a lower level can still be extraordinarily useful at work or enjoyable while travelling.關鍵期的存在並不意味著，11歲或者更大的孩子就得放棄了。有些人直到成年後還是非常優秀的語言學習者。哈茨霍恩還發現了一些需要多年學習才能掌握的語法難點。而一門語言，即使掌握的水平低一點兒，依然可能會在工作中相當有用，或者在旅行中增添樂趣。But for policymakers, the implication is clear. Earlier is better. Students outside the English-speaking world will eventually face English in the classroom or at work: they』ll have a better shot if they start younger. As for the Anglophone countries, getting foreign languages into the tender years is a hard sell. Many bureaucrats can hardly see past reading and maths. That is a mistake for many reasons. This study demonstrates one of them.但對於政策制定者來說，意義很明顯。越早，越好。非英語母語國家的學生終將在學校或者工作中面對英語：他們起步得越早，將越有利。而對於英語母語國家來說，把外語引入到兒童發展的早期，將很困難。很多官員還局限在閱讀和數學上。導致這一錯誤有很多原因。本研究揭示了其中的一個。