In this chapter, we will look briefly at the language development of young children. We will then consider several theories that have been offered as explanations for how language is learned. There is an immense amount of research on child language. Although much of this research has been done in middle-class North American and European families, there is a rich body of cross-linguistic and cross-cultural research as well. Our purpose in this chapter is to touch on a few main points in this research, primarily as a preparation for the discussion of second language acquisition (SLA), which is the focus of this book. 在本章中，我们将简要考察幼儿的语言发展，并讨论若干用于解释语言如何习得的理论。关于儿童语言的研究极为庞杂。尽管其中很大一部分是在北美和欧洲的中产阶级家庭中完成的，但跨语言与跨文化的研究也十分丰富。本章旨在概述这些研究中的若干要点，主要为随后关于第二语言习得（SLA）的讨论做铺垫——本书的核心即在于此。
Language acquisition is one of the most impressive and fascinating aspects of human development. We listen with pleasure to the sounds made by a three-month-old baby. We laugh and ‘answer’ the conversational ‘ba-ba-ba’ babbling of older babies, and we share in the pride and joy of parents whose one-year-old has uttered the first ‘bye-bye’. Indeed, learning a language is an amazing feat-one that has attracted the attention of linguists and psychologists for generations. How do children accomplish this? What enables a child not only to learn words, but to put them together in meaningful sentences? What pushes children to go on developing complex grammatical language even though their early simple communication is successful for most purposes? Does child language develop similarly around the world? How do bilingual children acquire more than one language? 语言习得是人类发展中最令人印象深刻且引人入胜的方面之一。我们乐于聆听三个月大婴儿发出的声音；我们会对更大些婴儿“ba-ba-ba”的“对话式”牙牙学语发笑并“回应”；当一岁的孩子第一次说出“bye-bye”时，我们与父母同感骄傲与喜悦。的确，学习语言是一项惊人的成就，数代语言学家与心理学家一直为之着迷。儿童如何做到这一点？是什么使得孩子不仅能学会词汇，还能将词组合成有意义的句子？在早期简单的交流对大多数目的已足够的情况下，是什么推动他们继续发展复杂的语法性语言？儿童语言在全世界的发展是否相似？双语儿童如何习得不止一种语言？
One remarkable thing about first language acquisition is the high degree of similarity in the early language of children all over the world. Researchers have described developmental sequences for many aspects of first language acquisition. The earliest vocalizations are simply the involuntary crying that babies do when they are hungry or uncomfortable. Soon, however, we hear the cooing and gurgling sounds of contented babies, lying in their beds looking at fascinating shapes and movement around them. Even though they have little control over the sounds they make in these early weeks of life, infants are able to hear subtle differences between the sounds of human languages. Not only do they distinguish the voice of their mothers from those of other speakers, they also seem to recognize the language that was spoken around their mother before they were born. Furthermore, in cleverly designed experiments, researchers have demonstrated that tiny babies are capable of very fine auditory discrimination. For example, they can hear the difference between sounds as similar as ‘pa’ and ‘ba’. 第一语言习得的一个显著特征，是世界各地儿童早期语言表现出高度相似性。研究者已描绘出第一语言习得多个方面的发展序列。最早的发声只是婴儿在饥饿或不适时的非自主哭泣。不久，我们便能听到满足的婴儿发出的咕咕声和咯咯声，他们躺在床上，注视周围迷人的形状与运动。尽管生命最初几周中他们几乎无法控制自己发出的声音，婴儿却能听辨人类语言声音之间的细微差异。他们不仅能区分母亲与他人声音，还似乎能识别出生前其母亲周围所使用的语言。此外，通过巧妙设计的实验，研究者表明，极小的婴儿具有极其精细的听觉辨别能力，例如，他们能分辨“pa”和“ba”这类极为相似的声音。
Janet Werker, Patricia Kuhl, and others have used new technologies that allow us to see how sensitive infants are to speech sounds. What may seem even more remarkable is that infants stop making distinctions between sounds that are not phonemic in the language that is spoken around them. For example, by the time they are a year old, babies who will become speakers of Arabic stop reacting to the difference between ‘pa’ and ‘ba’ which is not phonemic in Arabic. Babies who regularly hear more than one language in their environment continue to respond to these differences for a longer period (Werker, Weikum, and Yoshida 2006). One important finding is that it is not enough for babies to hear language sounds from electronic devices. In order to learn-or retain-the ability to distinguish between sounds, they need to interact with a human speaker (Conboy and Kuhl 2011). The Internet abounds with remarkable videos of infants reacting to language sounds. Janet Werker、Patricia Kuhl 等人利用新技术展示了婴儿对语音的敏感度。更为引人注目的是：婴儿会停止区分在其周围语言中并非音位性的声音。例如，至一岁时，将来讲阿拉伯语的婴儿不再对“pa”与“ba”的差别作出反应，因为该差异在阿拉伯语中并非音位对立。而在环境中经常听到不止一种语言的婴儿，会在更长时间内继续对这些差异作出反应（Werker, Weikum, and Yoshida 2006）。一个重要发现是：仅从电子设备中听到语言声音并不充分。为了学习——或保持——区分声音的能力，婴儿需要与人类说话者互动（Conboy and Kuhl 2011）。互联网上不乏婴儿对语言声音作出反应的精彩视频。
Whether they are becoming monolingual or bilingual children, however, it will be many months before their own vocalizations begin to reflect the characteristics of the language or languages they hear and longer still before they connect language sounds with specific meaning. However, by the end of their first year, most babies understand quite a few frequently repeated words in the language or languages spoken around them. They wave when someone says ‘bye-bye’; they clap when someone says ‘pat-a-cake’; they eagerly hurry to the kitchen when ‘juice and cookies’ are mentioned. 无论他们最终成为单语还是双语儿童，其自发发声反映所闻语言特征仍需数月时间，更需要更长时间才能将语言声音与特定意义建立联系。然而，到一岁末，大多数婴儿已能理解其周围所使用语言中相当数量的高频词汇。有人说“bye-bye”时他们会挥手；说“pat-a-cake”时会拍手；当提到“juice and cookies”时，他们会急切地奔向厨房。
At 12 months, most babies will have begun to produce a word or two that everyone recognizes. By the age of two, most children reliably produce at least 50 different words and some produce many more. About this time, they begin to combine words into simple sentences such as ‘Mommy juice’ and ‘baby fall down’. These sentences are sometimes called ‘telegraphic’ because they leave out such things as articles, prepositions, and auxiliary verbs. We recognize them as sentences because, even though function words and grammatical morphemes are missing, the word order reflects the word order of the language they are hearing and the combined words have a meaningful relationship that makes them more than just a list of words. Thus, for an English-speaking child, ‘kiss baby’ does not mean the same thing as ‘baby kiss’. Remarkably, we also see evidence, even in these early sentences that children are doing more than imperfectly imitating what they have heard. Their two- and three-word sentences show signs that they can creatively combine words. For example, ‘more outside’ may mean ‘I want to go outside again.’ Depending on the situation, ‘Daddy uh-oh’ might mean ‘Daddy fell down’ or ‘Daddy dropped something’ or even ‘Daddy, please do that funny thing where you pretend to drop me off your lap.’ 到12个月时，大多数婴儿会说出一两 个人人能听懂的词。到两岁时，大多数儿童能稳定地产出至少50个不同词汇，有些远不止此。此时，他们开始把词组合成简单句，如“Mommy juice”“baby fall down”。这种句子有时被称作“电报式”（telegraphic），因为其中省略了冠词、介词和助动词等。我们之所以将其辨识为句子，是因为尽管功能词与语法词缀缺失，词序却反映了他们所听语言的词序，且词语组合具有超越列表的语义关系。因此，对英语儿童而言，“kiss baby”与“baby kiss”并不相同。值得注意的是，即便在这些早期句子中，我们也能看到他们并非只是对所闻语言的拙劣模仿。他们的两词或三词句呈现出创造性组合的迹象。例如，“more outside”可表示“我还想再到外面玩”；依情境不同，“Daddy uh-oh”可能意味着“爸爸跌倒了”“爸爸掉了东西”，甚至“爸爸，请做那个把我假装从膝上掉下去的好玩动作”。
As children progress through the discovery of language in their first three years, there are predictable patterns in the emergence and development of many features of the language they are learning. For some language features, these patterns have been described in terms of developmental sequences or ‘stages’. To some extent, these stages in language acquisition are related to children’s cognitive development. For example, children do not use temporal adverbs such as ‘tomorrow’ or ‘last week’ until they develop some understanding of time. In other cases, the developmental sequences seem to reflect the gradual acquisition of the linguistic elements for expressing ideas that have been present in children’s cognitive understanding for a long time. For example, children can distinguish between singular and plural long before they reliably add plural endings to nouns. Correct use of irregular plurals (such as ‘feet’) takes even more time and may not be completely under control until the school years. 在生命最初三年探索语言的过程中，儿童在所学语言诸多特征的出现与发展上呈现可预测的模式。对于某些语言特征，这种模式被描述为发展序列或“阶段”。在一定程度上，这些习得阶段与儿童的认知发展相关。例如，在对时间有一定理解之前，儿童不会使用“tomorrow”“last week”这类时间副词。另一些情形下，发展序列似乎反映了儿童对表达早已存在于其认知中的观念所需语言要素的渐进习得。例如，儿童在能稳定地给名词加复数词尾之前，早已能辨别单复数；而不规则复数（如“feet”）的正确使用则需要更长时间，甚至直到学龄阶段才可能完全掌握。
In the 1960s, several researchers focused on how children acquire grammatical morphemes in English. One of the bestknown studies was carried out by Roger Brown and his colleagues and students. In a longitudinal study of the language development of three children (called Adam, Eve, and Sarah) they found that 14 grammatical morphemes were acquired in a similar sequence. The list below (adapted from Brown’s 1973 book) shows some of the morphemes they studied. 20世纪60年代，多位研究者聚焦于儿童如何习得英语中的语法词素。Roger Brown 及其同事与学生开展了一项著名研究。在对三名儿童（称为 Adam、Eve、Sarah）的语言发展进行的纵向研究中，他们发现14个语法词素的习得具有相似顺序。下表（据 Brown 1973 改编）列出其中若干被研究的词素。
present progressive -ing (Mommy running) 现在进行时 -ing（Mommy running）
plural -s (two books) 复数 -s（two books）
irregular past forms (Baby went) 不规则过去式（Baby went）
possessive -s (Daddy’s hat) 所有格 -’s（Daddy’s hat）