英语教学法原著选读50：克拉申二语习得五假说之四——输入假说（Input）

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导读：本篇是二语习得泰斗Stephen D. Krashen的著作《二语习得原则与实践（Principles and Practice of Second Language Acquisition）》第二章“第二语言习得理论”A节“有关第二语言习得的五个假说”中的第四个假说，探讨的是语言习得的实际过程。当代外语教学的基石i-->i+1，就是在这个假说中提出来的。按照这一假说，只要提供足够的、与真实语言环境相匹配的输入，学习者就能够自然地从现有的语言能力（i）进步到略高一层次的语言能力（i+1）。

本篇很长，将分三期刊出，本篇是第一篇。为促进朋友们多看英文原文，今天先不放译文，明天刊出。我在文中设置了五个空，没空一词，朋友们看看应该填什么，有兴趣的朋友可以试试填一下，明天我随译文公布答案。答全对的朋友会获得5分的积分，未来可以用于图书的兑换。

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原文

4. THE INPUT HYPOTHESIS

The important question is: How do we acquire language? If the Monitor hypothesis is correct, 1 acquisition is central and learning more peripheral, then the goal of our pedagogy should be to encourage acquisition. The question of how we acquire then becomes crucial.

(a) Statement of the hypothesis

Let us first restate the question of how we acquire: 2 the correctness of the natural order hypothesis, how do we move from one stage to another? If an acquirer is at "stage 4", how can he progress to "stage 5"? More generally, how do we move from stage i, where i represents current competence, to i + 1, the next level? The input hypothesis makes the following claim: a necessary (but not sufficient) condition to move from stage i to stage i + 1 is that the acquirer understand input that contains i + 1, where "understand" means that the acquirer is focussed on the meaning and not the form of the message.

We acquire, in other words, only when we understand language that contains structure that is "a little beyond" where we are now. How is this possible? How can we understand language that contains structures that we have not yet acquired? The answer to this apparent paradox is that we use more than our linguistic competence to help us understand. We also use context, our knowledge of the world, our extra-linguistic information to help us understand language directed at us.

The input hypothesis runs counter to our usual pedagogical approach in second and foreign language teaching. As Hatch (1978a) has pointed out, our assumption has been that we first learn structures, then practice using them in communication, and this is how fluency develops. The input hypothesis says the opposite. It says we acquire by "going for meaning" first, and as a result, we acquire structure! (For discussion of first language acquisition, see MacNamara, 1972.)

We may thus state parts (1) and (2) of the input hypothesis as follows:

(1) The input hypothesis relates to acquisition, not learning.

(2) We acquire by understanding language that contains structure a little 3 our current level of competence (i + 1). This is done with the help of context or extra-linguistic information.

A third part of the input hypothesis says that input must contain i + 1 to be useful for language acquisition, but it need not contain only i + 1. It says that if the acquirer understands the input, and there is enough of it, i + 1 will automatically be provided. In other words, if communication is successful, i + 1 is provided. As we will discuss later, this implies that the best input should not even attempt to deliberately aim at i + 1. We are all familiar with syllabi that try to deliberately cover i + 1. There is a "structure of the day", and usually both teacher and student feel that the aim of the lesson is to teach or practice a specific grammatical item or structure. Once this structure is "mastered", the syllabus proceeds to the next one. This part of the input hypothesis implies that such a deliberate attempt to provide i + 1 is not necessary. As we shall see later, there are reasons to suspect that it may even be harmful.

Thus, part (3) of the input hypothesis is:

(3) When communication is successful, when the input is understood and there is enough of it, i + 1 will be provided automatically.

The final part of the input hypothesis states that speaking fluency cannot be taught directly. Rather, it "emerges" over time, on its own.4 The best way, and perhaps the only way, to teach speaking, according to this view, is simply to provide comprehensible input. Early speech will come when the acquirer feels "ready"; this state of readiness arrives at somewhat different times for different people, however. Early speech, moreover, is typically not grammatically accurate. Accuracy develops over time as the acquirer hears and understands more input. Part (4) of the input hypothesis is thus:

(4) Production ability emerges. It is not taught directly.

(b) Evidence supporting the hypothesis

(i) First language acquisition in children. The input hypothesis is very consistent with what is known about "caretaker speech", the modifications that parents and others make when talking to young children. The most interesting and perhaps the most important characteristic of caretaker speech for us is that it is not a deliberate attempt to teach language. Rather, as Clark and Clark (1977) point out, caretaker speech is modified in order to aid comprehension. Caretakers talk "simpler" in an effort to make themselves 4 by the child.

A second characteristic of interest to us here is the finding that caretaker speech, while it is syntactically simpler than adult-adult speech, is "roughly-tuned" to the child's current level of linguistic competence, not "finely-tuned". In other words, caretaker speech is not precisely adjusted to the level of each child, but tends to get more complex as the child progresses. Very good evidence for rough-tuning comes from the research of Cross (1977) and Newport, Gleitman, and Gleitman (1977), who report that correlations between input complexity and measures of the child's linguistic maturity, while positive and often significant, are not usually very large. An interpretation of this finding is that caretakers are not taking aim exactly at i + 1. The input they provide for children includes i + 1, but also includes many structures that have already been acquired, plus some that have not (i + 2, i + 3, etc.) and that the child may not be 5 for yet. In other words, caretakers do not provide a grammatically based syllabus! (For a more complete review of rough-tuning, see Krashen 1980, 1981.)

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