些错误业可被学习者用作验证某些假设的手段( Corder 1967) 。
Chomsky(1965)对母语习得本质的阐述为70年代初的二语习得研究提供了新的理论基础。Chomsky 认为, 行为主义的观点无法解释语言习得中的两个基本事实: ( 1) 儿童能够创造性地使用语言, 他们能够理解和使用以前从未听说或接触过的语言; ( 2) 即使是在有缺陷的语言环境中,儿童依然可以系统地获得语言。他认为, 创造性是语言的本质之一, 人类语言的这一特性是无法以任何形式的―刺激—反应‖学习方式来习得的。人类的这种语言能力只能来自于人的大脑本身, 而不是外界因素影响的结果。
他提出区分―语言能力‖（linguistic competence）---人们内化了语言规则体系和―语言表现‖（linguistic performance）----语言能力的实际运用，即人实际说出来的话语。他认为语言表现不能全面反应语言能力，只就有限的实际话语（语言表现）进行结构分析，不能揭示语言的本质，无法解释人类语言创造性的特征。语言学需要研究的是能使人掌握语言的规则体系、说出无限话语的人类的认知结构中的语言能力。他提出―语言习得机制‖（language acquisition device）和―普遍语法‖（universal grammar）的假说，把语言学研究的触角伸向人类认知领域，探讨语言的心理过程。称之为―乔姆斯基革命‖标志着转换生成语法学派的出现。转换生成语法时期，把语言看做是人的一种能力。依靠这种能力，人们可以掌握复杂的、受规则支配的语言生成体系，创造性地运用语言。这一观点成为重视发挥学习者的智力，强调认知语法规则的认知法的理论基础。（功能主义语言学（弗斯（J.R.Firth），韩礼德（M.Z.K.Halliday））把语
言看做是一种社会现象，强调研究语言的社会功能。这一理论影响了以培养语言交际能力为目标的交际法。）
Selinker 于1972 年发表了著名的Interlanguage 一文, 提供了中介语的概念。他认为, 二语学习者在某一特定时期所掌握的语言体系既有别于其母语, 也有别于二语, 而是一种独立的语言体系, 即中介语系统。Selinker 认为, 二语习得与第一语言习得之间最主要的区别在于, 大部分二语学习者的中介语在发展过程的某一阶段出现了石化现象( fossilization) , 大约只有5%的人能够达到中介语连续体的终端。Slinker 指出, 这部分人之所以能够成功, 是因为他们利用了人脑中的潜在语言机制( latent language structure) , 这种机制类似于Chomsky 的语言习的机制( LAD:language acquisition device) 概念。More--错误分析理论及其对外语教学的启示
The Critical Period Hypothesis
1959年,著名外科手术医生潘费尔德 ( Penfield)提出了人对于外部环境和刺激存在一个反应敏感的关键期 (Critical Period)这一说法。1967年列尼伯格 (Lenneberg)在对潘费尔德的结论做了大量研究后,在他的著作《语言生物学基础 》 (Biological Foundations of Language)中提出了著名的关键期假说 (Critical Period Hypothesis)。所谓的发展关键期指的是大脑的可塑性于某个时期后呈固定的状态。Competence reaches its peak during a \period\Newport 1993). 他认为,语言学习能力限定在青春期 ( Puberty) ,因为在青春期后,随着大脑侧化 (Lateralization)的完成,人的语言学习能力会渐渐消失。
There are different sensitive periods for different components of language. Almost everybody seems to agree that the sensitive period for phonology ends at around age 5 or 6 (which could explain why second language acquisition which begins later may never attain native or near native like accent) whereas the critical period for morphology and syntax declines later, probably at the onset of puberty (Long 1990).
*A brief history of the field: 1970s
Emphasis on the acquisition of grammatical morphemes语法词素习得
Emphasis on innate universals of language acquisition普遍语法与二语习得
De-emphasis of the effects of the first language on the learning of a second language L1与L2的关系
The first theory of second language acquisition
Transformational generative grammar
The Standard Theory (ST) of transformational generative grammar was first formulated in Chomsky's (1965) Aspects of the Theory of Syntax. 80年代以后又称“管辖与约束理论（Govemment and Binding Theory）”和“原则与参数理论（Principle and Parameter Theory）”。
转换生成语法（Transformational—Generative grammar）的四条基本原则是:
（1）任何语言都具有生成性，而这种生成性是由规则控制的。这意味着语言教学必须是一个有目标、有计划、有步骤的过程体系。
（2）语法规则存在于人的大脑中。人能够自发地运用语法规则，并不意味着语法规则只能自然习得。掌握一种语言技能需要主观努力;而要达到自然、流畅则需要不断使用它。
（3）人脑有天然的机能，能学会任何语言。学习语言是人类特有的行为活动。一个人只要处在一个有意义地使用语言的环境中，他就能学会这种语言，不管他年龄有多大。儿童先天就具备一种语言习得机制(LAD)。
（4）任何活的语言，我们都可以通过其进行思考。语言、思维和意义是紧密相连的。学习一种语言，就要用这种语言去思考。有意义地使用这种语言，比机械的句型操练更能帮助人们获得这种语言的思维和运用能力。
普遍语法假说(the Universal Grammar)，即语言是所有语言使用者所共有的生理天赋,不必通过学习而存在于大脑中。1991年，乔姆斯基阐明了普遍语言的原则和参数理论(the Principles and Parameters Theory)。
乔姆斯基认为普遍语法是人类一切语言都必须具有的原则、条件和规则系统,是人类通过生物进化和遗传先天获得的;个别语法（Particular Grammar）则
是人出生以后通过学习获得的。普遍原则和参数是普遍语法的两大组成部分,合称为核心语法，是语言中最本质的部分，是不用学的，天生的。
以乔氏为代表的语言习得天生派（Nativism)认为儿童先天就具备一种语言习得机制(LAD)，后天的语言输入只是起到激活这个机制的作用，在特定的环境中选择某种语言参数(parameter)，习得便自然产生。这个观点否认了语言输入的关键作用，把习得的产生归因于内在的先天因素。
The UG theory considers that the input from the environment is insufficient to account for language acquisition. In the same perspective, White (2003:22) says that “[I]f it turns out that the L2 learner acquires abstract properties that could not have been induced from the input, this is strongly indicative that principles of UG constrain interlanguage grammars, parallel to the situation of L1 acquisition‖. As Mitchel and Myles (2004:94) remind us, ―The universal Grammar approach is only interested in the learner as a processor of a mind that contains language‖ and not as a social being.
More
The Innateness Hypothesis
The cognitive revolution of the 1950s put forth the idea that there is a mental basis for language. The view of language as an independent, unique cognitive system, which involves innate, faculty-specific mechanisms, replaces the view that language is response and stimulus.
? Language is an independent, unique, species-specific
cognitive system, which involves specific mechanisms.
? The process of language acquisition reflects a cognitive
capacity which is biologically determined; some aspects of language knowledge are innate.
? Knowledge of language develops in the child without conscious
effort or formal instruction, it is the same for every individual and it is distinct from more general cognitive abilities.
? The language faculty is analogous to other biological systems;
but it also has properties which are unusual among biological systems.
The process of acquisition reflects a cognitive capacity which is biologically determined (MacWhinney and Bates 1989:10, 26).
The crucial part of this species-specific property is defined by Chomsky (1980:33-34) as:
Were it not for this highly specific innate endowment, each individual would grow into some kind of amoebic creature, merely reflecting external contingencies, one individual quite unlike another, each utterly impoverished and lacking the intricate special structures that make possible a human existence and that differentiate one species from another.
*A brief history of the field: 1980s
A return to the recognition that a learner‘s first language can affect second language acquisition in important ways
Emphasis on variables that can affect how quickly and how well a person learns a second language 二语习得的环境因素
Multiple new theories related to second language acquisition Attention to the acquisition of pragmatics 语用习得 Emphasis on input语言输入
*A brief history of the field: 1990s
Increased attention to vocabulary acquisition词汇习得 Emphasis on form-function mappings形式-功能映射
Increased awareness of the complex ways in which variables can interact二语习得的环境因素
Increased attention to the details of learners‘ backgrounds, their learning contexts, and the specific decisions they make in their learning process学习者个体
Emphasis on interaction 交互假说 Long（1996）
重要的二语习得理论-- 在第二语言习得研究中成就最大、影响最广也是最全面的理论便是克拉申（S.D.Krashen）的语言习得理论。他的理论实际上是对近几十年来第二语言或外语学习研究的总结，并把各种研究超过加以理论化、系统化，使之成为系统的学说。
斯蒂芬.克拉申(Stephen Krashen)1941年出生于美国
芝加哥，现为美国南加州大学荣休教授，他毕生致力于第二语言习得的研究，这为他赢得了世界性声誉。克拉申在20世纪中叶以来提出的第二语言习得的―输入假说模式‖，这是近几十年来影响广泛、解释全面又很具争议性的理论。早在1970 年代初克拉申就提出了―监控模式‖(The Monitor Model) ,该模式以―监控假说
（ The Monitor Hypothesis）‖为核心;80 年代中叶,克拉申对之进一步扩充修订,转为以―输入假说‖(The input hypothesis) 为中心,形成了―输入假说模式‖。具体而言,―输入假说模式‖由五个互相联系的核心假说构成,它们分别是: ①语言习得- 学得（The Acquisition—Learning Hypothesis）假说; ②自然顺序假说（The Natural Order Hypothesis）; ③监控假说; ④语言输入假说; ⑤情感过滤假说（The Affective Filter Hypothesis）。这五个假说彼此联系、互相补充,构成了一个有机整体。
Overview:
Krashen‘s (1985) Input Hypothesis is an attempt to explain how a learner ?acquires‘ a second language, not ?learns‘ (see Krashen 1985).
He believed that a learner improves and progresses along a natural order when receiving input that is one step beyond the learner‘s current stage of linguistic competence (i+1), claiming that
comprehensible input was not only necessary but also sufficient for successful SLA to take place. He suggested that natural communicative input was the key to designing a syllabus, giving all learners some i+1 input.
克拉申理论主要由以下五个假说组成：
1 习得---学得区别假说（The Acquisition—Learning Hypothesis） 克拉申理论的出发点和核心是他对―习得‖和 ―学得‖的区分，以及对它们各自在习得者第二语言能力形成过程中所起的作用的认识。―习得‖是潜意识过程，是注意意义的自然交际的结果，儿童习得母语便是这样的过程。习得的语言系统处于大脑左半球语言区，是自发语言运用的根本。与之相对的是―学得‖，这是个有意识的过程，即通过课堂教师讲授并辅之以有意识的练习、记忆等活动，达到对所学语言的了解和对其语法概念的―掌握‖。―学得‖的系统虽然在大脑左半球，但不一定在语言区。克拉申认为，只有―习得‖才能直接促进第二语言能力的发展，才是人们运用语言时的生产机制；而对语言结构有意的了解作为―学得‖的结果，只能在语言运用中起监控作用，而不能视为语言能力本身的一部分。
Language acquisition: the process where a language is acquired as a result of natural and largely random exposure to language.( a
subconscious process) Krashen describes this process as a ?natural‘ one, where there is no ?conscious focusing on linguistic forms. According to his argument, acquisition refers to the way children learn their native language.
Language learning: the process where the exposure to language is structured through language teaching. Learning is a conscious process, and it usually takes place in the language classroom.
Acquisition Learning implicit, subconscious explicit, conscious informal situations formal situations uses grammatical 'feel' uses grammatical rules depends on attitude stable order of acquisition depends on aptitude simple to complex order of learning