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Neuroscientists have long observed that learning a language presents a different set of opportunities and challenges for adults and children。
Adults easily grasp the vocabulary needed to navigate a grocery store or order food in a restaurant, but children have an innate ability to pick up on subtle nuances of language that often elude adults。
For example, within months of living in a foreign country, a young child may speak a second language like a native 
speaker。
Experts believe that brain structure plays an important role in this “sensitive period” for learning language, which is believed to end around adolescence。
The young brain is equipped with neural circuits that can analyze sounds and build a coherent set of rules for constructing words and sentences out of those sounds。
Once these language structures are established, it’s difficult to build another one for a new language。
持久以来，神经学家一向认为说话的进修对成年人和孩子来讲有着分歧的机会与挑战。
成年人很轻易地把握杂货店或餐馆必备辞汇，孩子就有与生俱来能力，分辨说话中渺小的不同，而这些不同常常会把成年人难住。
例如说，孩子只要在外洋糊口几个月，便可以像外国人同样说外语。
一些专家认为大脑布局会影响人们说话进修的敏感期，而敏感期止于芳华期。
孩子的大脑含有神经回路，可以或许阐发声音，创建起一套联贯的法则，从而操纵这些声音组词造句。
这些说话布局创建完成，大脑就很难构成新的布局，进修新一门说话。
In a new study, a team of neuroscientists and psychologists from Massachusetts Institute of Technology (MIT) discovered another factor that contributes to adults’ language difficulties: When learning certain elements of language, adults’ more highly developed cognitive skills actually get in the way。
The researchers discovered that the harder adults tried to learn an artificial language, the worse they were at deciphering the language’s morphology —the structure and deployment of linguistic units such as root words, suffixes, and prefixes。
“We found that effort helps you in most situations, for things like figuring out what the units of language that you need to know are, and basic ordering of elements. But when trying to learn morphology, at least in this artificial language we created, it’s actually worse when you try,” said Amy Flynn a postdoc at MIT’s McGovern Institute for Brain Research。
Finn and colleagues from the University of California at Santa Barbara, Stanford University, and the University of British Columbia describe their findings in journalPLOS ONE。
Linguists have known for decades that children are skilled at absorbing certain tricky elements of language, such as irregular past participles (examples of which, in English, include “gone” and “been”) or complicated verb tenses like the subjunctive。
“Children will ultimately perform better than adults in terms of their co妹妹and of the gra妹妹ar and the structural components of language —some of the more idiosyncratic, difficult-to-articulate aspects of language that even most native speakers don’t have conscious awareness of,” Finn says。
In 1990, linguist Elissa Newport hypothesized that adults have trouble learning those nuances because they try to analyze too much information at once. Adults have a much more highly developed prefrontal cortex than children, and they tend to throw all of that brainpower at learning a second language。
This high-powered processing may actually interfere with certain elements of learning language。
“It’s an idea that’s been around for a long time, but there hasn’t been any data that experimentally show that it’s true,” Finn says。
Finn and her colleagues designed an experiment to test whether exerting more effort would help or hinder success。
在一项钻研中，由来自麻省理工学院(MIT)神经学家及生理学家构成的钻研团队发明另外一种身分，可以诠释成年人进修说话的难点：在进修说话的某一方面时，成年人高度发财的认知技术现实上阻碍了说话的进修。
钻研职员发明，成年人在进修人造说话的进程中越尽力，那末他们在进修说话形态学方面表示就越糟。(形态学指的是词根、后缀及前缀等说话单元的布局及组合。)
“钻研发明，大都环境下，尽力有所感化，好比，你想要解出你必要晓得的是那种说话单元及根本的成份次序放置。可是，当你想要进修形态学的时辰，进修咱们本身缔造的说话时，越尽力，结果越差。”麻省理工学院麦戈文人脑钻研所的博士后艾米·弗林(Amy Flynn)暗示。
来自加州圣巴巴拉大学、斯坦福大学及英属哥伦比亚大学的芬恩(Finn)及同事在《大众科学藏书楼·综合》杂志上颁发了他们的钻研功效。
几十年来，说话学家都晓得孩子长于消化吸取说话进修中的难点问题，像是不法则曩昔分词(英语中的例子，好比“gone”和“been”)或是虚拟语气中繁杂的动词时态。
“对付语法及句式布局，孩子总会比成年人把握地更好，好比，即即是说母语的人大[微博]多也没有意想到的一些比力特别、发音坚苦的问题等。”芬恩说。
1990年，说话学家爱丽莎·纽波特(Elissa Newport)提出一个假如，成年人理解这种渺小不同有坚苦是由于他们试图同时阐发过多的信息。成年人的前额皮质比起孩子，加倍高度发财，他们常常会挖空心思去进修第二门说话。
究竟上，这个高强度的进修进程或许会滋扰某些说话进修身分。
“这个设法已存在多时，可是今朝为止，没有任何实行数据证实它的准确性。”芬恩说。
芬恩及同事设计了一个实行，测试支出更多的心力是不是有助于或有碍于说话进修。
The Study
钻研进程
First, they created nine nonsense words, each with two syllables. Each word fell into one of three categories (A, B, and C)， defined by the order of consonant and vowel sounds。
Study subjects listened to the artificial language for about 10 minutes. One group of subjects was told not to overanalyze what they heard, but not to tune it out either。
To help them not overthink the language, they were given the option of completing a puzzle or coloring while they listened. The other group was told to try to identify the words they were hearing。
Each group heard the same recording, which was a series of three-word sequences —first a word from category A, then one from category B, then category C —with no pauses between words。
Previous studies have shown that adults, babies, and even monkeys can parse this kind of information into word units, a task known as word segmentation。
起首，他们缔造了九个毫偶然义的词，每一个词两个音节。再按照子音及缘由的分列，将这些词分为三类(A、B及C类)。
钻研工具听这些人造说话约莫10分钟。此中一组被告诉不要过分阐发他们听到的内容，也不要视而不见。
为了避免让他们过分阐发，他们可以选择在听的进程中完成拼图或给图上色。此外一组被告诉要尽可能辨析他们听到的内容。
每一个小组听的都是一样的内容，三个单词为一个单元，第一个为A类词，第二个B类，接着C类，词与词中心没有搁浅，
既往钻研显示成年人、孩子，乃至是山公都能理解这种单词组信息，亦被称为“词切分”。
Subjects from both groups were successful at word segmentation, although the group that tried harder performed a little better. Both groups also performed well in a task called word ordering, which required subjects to choose between a correct word sequence (ABC) and an incorrect sequence (such as ACB) of words they had previously heard。
The final test measured skill in identifying the language’s morphology。
The researchers played a three-word sequence that included a word the subjects had not heard before, but which fit into one of the three categories。
When asked to judge whether this new word was in the correct location, the subjects who had been asked to pay closer attention to the original word stream performed much worse than those who had listened more passively。
The findings support a theory of language acquisition that suggests that some parts of language are learned through procedural memory, while others are learned through declarative memory。
Under this theory, declarative memory, which stores knowledge and facts, would be more useful for learning vocabulary and certain rules of gra妹妹ar。
两组实行工具都能乐成地完成词切分，固然当真阐发的那组表示更好一点。一样地，在辞汇次序分列的使命中，两组也都完成得很好。第二个使命请求实行工具在听过的准确顺序(ABC)与毛病词序(ACB)中作出选择。
终极测试考量他们在分辨说话形态方面的技术。
钻研职员播放连续串三词组和，此中包含他们没有听过的词序，但也合适分类请求。
当为请求对新词词序作出果断时，当真阐发原词语流的那组实行工具表示比消极地听的那组差很多。
钻研成果与说话习得的一个理论符合，那就是，说话的某些部门是经由过程步伐影象进修来的，但是其他的一些是由报告性影象习得的。
在该理论系统下，报告性影象，用于贮存常识与究竟，这类影象在辞汇与某些语律例则的进修中感化更较着。
Procedural memory, which guides tasks we perform without conscious awareness of how we learned them, would be more useful for learning subtle rules related to language morphology。
“It’s likely to be the procedural memory system that’s really important for learning these difficult morphological aspects of language。
“In fact, when you use the declarative memory system, it doesn’t help you, it harms you,” Finn says。
Still unresolved is the question of whether adults can overcome this language-learning obstacle. Finn says she does not have a good answer yet but she is now testing the effects of “turning off” the adult prefrontal cortex using a technique called transcranial magnetic stimulation。
Other interventions she plans to study include distracting the prefrontal cortex by forcing it to perform other tasks 
while language is heard, and treating subjects with drugs that impair activity in that brain region。
步伐性影象，引导咱们在不领会进修方法的环境下完成使命，这类影象在说话形态相干的奥妙法则进修中感化更较着。
“在较有难度的说话形态学方面的进修中，步伐性和体系可能阐扬着更大的感化。”
“究竟上，利用报告性影象系统，其实不起感化，反而是帮倒忙。”芬恩说。
使人未解的还是成年人是不是可以或许降服说话进修的停滞。芬恩说她也没有一个公道的谜底，可是如今她正利用叫做经颅磁刺激的技能，测试“封闭”成年人前额皮质的感化。
她还规划钻研其他方面的滋扰，好比在听的进程中，经由过程强迫性地完成使命，滋扰前额皮质，利用药物影响大脑特定区域的勾当等。
