儿童与成人外语学习差异说.ppt

7.4 Explanations to Child and Adult L2 learning （儿童与成人外语学习差异原因说）,For explanations survey the differences between child and adult learners of second language from different perspectives and provide biological, cognitive and affective explanations for second language learning.,In biological explanations for optimal age of L2 learning, the considerations are most prominent and influential .They are 1.the critical period hypothesis . 2.neurological considerations 3.psychomotor considerations,7.4.1 Biological explanations,1)The critical period hypothesis,The critical period hypothesis Initially the notion of critical period was proposed by Lenneberg(伦内伯格) in 1967. And was only connected to first language acquisition .Later, L2 researchers have outlined the possibilities of extrapolating the critical period hypothesis to L2 learning, too.,Definition of the critical period,The critical period states that there is a period when language acquisition takes place naturally and effortlessly. It is a biologically determined period of life when language can be acquired more easily and beyond which time language becomes increasingly difficult to learn . The hypothesis claims that there is such a biological timetable for all language learners. It argues that the optimum age for language acquisition falls within the ten first ten years of life. A critical point for L2 learning occurs around puberty.,During this period the brain retains plasticity, but with the onset of puberty this plasticity begins to disappear and learners seem to be relatively incapable of acquiring a native-like intonation and pronunciation of second language. Some research (Lenneberg 1976) suggests that this is the result of the lateralization（边化，偏侧性） of the language function in the left hemisphere of the brain.,1.The critical period hypothesis is an inadequate account of the role played by age in SLA, because this assumption is only partially correct .pronunciation or accent is not the only criterion of successful L2 learning in term of success or rate of acquisition . As Ellis (1985)points out that the critical period hypothesis needs to be recast to account for why loss of plasticity affects pronunciation but not other levels of language .,Others opinions about critical period hypothesis,2.Some psycholinguists raised doubts about “one single and unified critical period” hypothesis and proposed instead the “multi_critical period” hypothesis (Seliger 1978).They argued that process of the lateralization and localization of language function is a gradual one ,carrying on over many years. In general , the evidence linking cerebral dominance and age differences in learners in not clear yet .,2) Neurological considerations,1.One of the most interesting areas of inquiry in L2 learning has been the study of the function of the brain in the process of language acquisition . Some scholars have found out that the lateralization of the human brain is the key to questions of L2 learning.,2.There is evidence in neurological research that as the human brain matures certain other functions to the right hemisphere. Language functions appear to be controlled mainly in the left hemisphere and children are born with predisposition to the left hemisphere,Left hemisphere:,Intellectual, logical, and analytic functions Language mainly controlled,Right hemisphere:,emotional and social needs,. 3.There is a relationship between lateralization and L2 learning because lateralization takes place around the age of 2 and is completed around puberty. 4.Therefore the plasticity of brain prior to puberty enables children to acquire languages easily and the accomplishment of lateralization after puberty makes it difficult for adults to learn a fluent language .,3) Psychomotor considerations,There role of the psychomotor coordination of the “speech muscles” in L2 learning is stressed here .,Henry Kissinger Effect,Henry Kissinger Effect He is the former U.S. Secretary of State, whose German accent was so noticeable ,yet who was more eloquent than the large majority of native speakers.,们认为人类的语言学习有一个由生物因素决定的关键期，它开始于二周岁，到青春期结束，青春期大脑侧化或分化后，失去可塑性，过了这个时期,语言学习就会很困难而且不易成功目前比较有影响的另一种先天决定论是伦内伯格的“关键期理论”，也有文献称之为“自然成熟说”1。 1967年伦内伯格发表了他的重要著作“语言的生物学基础”（The Biological Foundation of Language）。在该书中，他提出一套用于判定是否属于“先天能力”的准则，并且证明人类的语言能力完全符合这一套准则，所以是先天的。他把儿童的语言发展看成是受发音器官和大脑等神经机能制约的自然成熟过程。伴随年龄的增长，儿童的发音器官和大脑的神经机能逐渐成长发育。当和语言有关的生理机能成熟到一定的准备状态时，只要受到适当外界条件的激活，就能使潜在的与语言相关的生理机能转变为实际的语言能力，所以儿童语言能力的获得是由先天遗传因素决定的。伦内伯格还指出，在儿童发育期间，语言能力开始时是受大脑右半球支配，以后，逐渐从右半球转移到左半球，最后才形成左半球的语言优势（左侧化）。伦内伯格认为，左侧化过程发生在两岁至12岁之间，并强调这是儿童语言发展的关键时期：在这一时期之后，如果大脑左半球受损，将会造成严重的语言障碍，甚至终生丧失语言能力；如果是在这一关键时期的开始或中间阶段（即左侧化完成之前）左半球受损，则语言能力将继续留在右半球而不受影响。这就是伦内伯格关于儿童语言发展的“关键期理论”。 从当前脑神经科学研究的进展来看，伦内伯格关于儿童发育早期（四、五岁之前）语言能力是受右脑控制的观点是值得商榷的，至少还没有得到实验证据的支持。目前比较公认的看法是：儿童在青春期之前（尤其在10岁之前），大脑两半球都具有发展语言的潜在机能，在语言能力发展上两半球是处于竞争状态，这时尚不存在单侧优势。只是随着年龄增长和社会交往的增加，对言语能力要求愈来愈高，需要相关神经机制的更为精细的调节与控制，加上人类的大脑结构有天生的不对称性瓦达（Wada）等人对胎儿大脑的研究表明4，其左半球的颞叶均比右半球略大，而颞叶正是与话语理解密切相关的部分，最后才在两半球竞争过程中逐渐形成左半球的言语功能优势。 尽管有这类争议，但是就伦内伯格的“关键期”理论本身而言，我们还是应当给以充分的肯定和高度的重视。事实上，儿童获得语言具有“关键期”（也称最佳敏感期），现在已不再是一种“假说”，而是已得到许多实验与观察证实的科学事实。例如： 加拿大多伦多大学语言学家J.K.Chambers在1992年发表“方言习得”5一文。该文根据六名加拿大儿童移居英国习得英国南部方言的案例，发现对于新方言的复杂规则和新音位，7岁和不到7岁的儿童（早期习得者）可以顺利习得；14岁和14岁以上者（晚期习得者）几乎不能顺利习得，甚至永远不能完全掌握；7至14岁之间的儿童则界于这二者之间（可能是早期习得者，也可能是晚期习得者）。这一研究表明语言获得确实有一关键期。 美国Rutgers大学认知科学中心K.Stromswold在1995年发表的文章中指出6，婴儿期的脑损伤通常只造成暂时的、较轻的语言缺陷，而成人发生的同样脑损伤则会造成长期的、严重的语言障碍。儿童失语症较容易康复与两个脑区可以实现语言功能重构有关：第一脑区是与受损伤的左半球语言功能区相毗邻的脑区；第二脑区是与左半球受损脑区相对应的右半球未受损脑区（即右半球上解剖结构相同的脑区）。如果左半球语言功能区的损伤面积很大，以至其周围几乎没有未受损脑区时，右半球的对应区域就将承担起语言功能重构的全部功能。一般来说，重构的效果（即失语症的康复情况）年龄愈小愈好。 K.Stromswold在分析了众多的语言获得案例（这些案例中包括正常儿童、失聪者、在极端社会条件和语言剥夺条件下成长的儿童、不同年龄的第二语言习得者）以后，最终得出结论：在关键期以后，人类获得语言的能力随年龄的增长而削弱。 为了检验第二语言的获得是否也存在关键期，Johnson和Newport研究了本族语是朝鲜语和汉语的一批被试的英语能力7，这些被试是在后来进入英语环境后才开始学习英语，但进入英语环境的时间有所不同，最早的3岁，最晚的39岁。实验研究结果表明，对于青春期（约14岁）开始前进入英语环境的被试，其掌握英语,Human cognition develops rapidly throughout the first 16 years of life and the cognitive development slows down to some extent after adulthood. Child is a concrete thinker and adult can think formally and abstractly.,7.4.2 Cognitive Explanation,7.4.3 Affective Explanations,Human beings are emotional creatures. Such as anxiety, motivation, empathy and so on .young children a