Positive-and-Negative-Evidence-in-Language-Acquisition知识讲解

1、Po s i t i v e - a n d -Ne g a t i v e -Ev i de n c e- i n -Language-Ac q u i s i t i o nPositive and Negative Evidence in Language Acquisition1IntroductionThe necessity for input in the process of second language acquisition (SLA) is a well- accepted fact, but the form and type that it needs to tak

2、e for learning to occur remains a controversial issue. Those subscribing to a nativist or rationalist position of acquisition support the idea that positive evidence is all that is required for acquisition to occur (Chomsky, 1989). They believe that human knowledge develops from structures, processe

3、s and ideas that are in the mind at the birth. On the other hand, those working within the interactionist paradigm see positive evidence as insufficient and propose a role for both positive and negative evidence (Labov, 1969; Gass, 2003).2. Positive EvidencePositive evidence is evidence that a parti

4、cular utterance is grammatical in the language that the language that the child is learning. It consists of descriptive information about a form or an utterance. It consists of actually occurring sequences, i.e. sentences of the language. Various options exist for positive evidence including plentif

5、ul exemplars of the target feature without any device to draw attention to it. For example, Trahey (1996) developed materials consisting of stories, games, and exercises with the aim of simply exposing learners to the subject. In this case, acquisition occurs as a result of frequent exposure to a ta

6、rget feature. It involves some sort of attempt to highlight instances of the target feature, thus drawing learners attention to it.Positive evidence can function entirely by itself. Learners can simply be asked to listen to or read texts that have been provided. It can also be accompanied by some ki

7、nd of meaning-focused activity that incidentally assists learners to focus their attention on the target feature.For example, comprehension questions that can only be answered correctly if the learners process the target feature. There are tasks that are designed to elicit production of a specific t

8、arget feature in the context of performing a communicative task, and tasks that are intended to result in learners employing some feature that has been specifically targeted (White, 1987).Several patterns in language have been claimed to be unlearnable from positive evidence alone. One example is th

9、e hierarchical nature of languages. For any given set of sentences generated by a hierarchical grammar capable of infinite recursion there are an indefinite number of grammars that could have produced the same data. This would make learning any such language impossible. Indeed, a proof by E. Mark Go

10、ld showed that any formal language that has hierarchical structure capable of infinite recursion is unlearnable from positive evidence alone, in the sense that it is impossible to formulate a procedure that will discover with certainty the correct grammar given any arbitrary sequence of positive dat

11、a in which each utterance occurs at least once. However, this does not preclude arriving at the correct grammar using typical input sequences rather than particularly malicious sequences or arrive at an almost perfect approximation to the correct grammar.Another example of language pattern claimed t

12、o be unlearnable from positive evidence alone is subject-auxiliary inversion in questions, i.e.:?You are happy.?Are you happy?There are two hypotheses the language learner might postulate about how to form questions: (1) The first auxiliary verb in the sentence (here: are) moves to the beginning of

13、the sentence, or (2) the main auxiliary verb in the sentence moves to the front. In the sentence above, both rules yield the same result since there is only one auxiliary verb. But, the difference is apparent in this case: ?Anyone who is interested can see me later.1.Is anyone who interested can see

14、 me later?2.Can anyone who is interested see me later?Of course, the result of rule (1) is ungrammatical while the result of rule (2) is grammatical. So, rule (2) is (approximately) what we actually have in English, not rule(1). The claim, then, first is that children dont see sentences as complicat

15、ed as this one enough to witness a case where the two hypotheses yield different results, and second that just based on the positive evidence of the simple sentences, children could not possibly decide between (1) and (2). Moreover, even sentences such as (1) and (2) are compatible with a number of

16、incorrect rules (such as front any auxiliary). Thus, if rule (2) was not innately known to infants, we would expect half of the adult population to use (1) and half to use (2). Since that doesnt occur, rule (2) must be innately known.3. Negative EvidenceNegative evidence refers to information about

17、which strings of words are not grammatical sentences in the language, such as corrections or other forms of feedback from a parent that tell the child that one of his or her utterances is ungrammatical. Negative evidence consists of information about the impossibility and ungrammaticality of a form

18、or an utterance. In other words, negative evidence such as explanations, explicit grammar teachings, and corrections of wrong sequences or ungrammatical sentences, show what may not be done. It needs additional evidence from corrections of impossible sequences, reading the rule-books, comprehending

19、abstract explanations, and so on. There are times when a learner supplies a linguistically incorrect response in reply to a teachers initiation; the teacher tends to provide direct, explicit, overt negative evidence. However, Chomsky (1981) holds the idea that direct negative evidence is not necessa

20、ry for language acquisition, but indirect negative evidence may be relevant. Its very important for us to know whether children get and need negative, because in the absence of negative evidence, any child who hypothesizes a rule that generates a superset of the language will have no way of knowing

21、that he or she is wrong. If children dont get, or dont use, negative evidence, they must have some mechanism that either avoids generating too large a language the child would be conservative - or that can recover from such overgeneration.There is also much criticism about whether negative evidence

22、is really so rarely encountered by children. Pullum argues that learners probably do get certain kinds of negative evidence. In addition, if one allows for statistical learning, negative evidence is abundant. Consider that if a language pattern is never encountered, but its probability of being enco

23、untered would be very high were it acceptable, then the language learner might be right in considering absence of the pattern as negative evidence.Chomsky accepts that this kind of negative evidence plays a role in language acquisition, terming it indirect negative evidence, though he does not think

24、 that indirect negative evidence is sufficient for language acquisition to proceed without Universal Grammar.However, contra this claim, Ramscar and Yarlett (2007) designed a learning model that successfully simulates the learning of irregular plurals based on negative evidence, and backed the predi

25、ctions of this simulation in empirical tests of young children. Ramscar and Yarlett suggest that failures of expectation function as forms of implicit negative feedback that allow children to correct their errors.As for the argument, its not clear that human languages are truly capable of infinite r

26、ecursion. Clearly, no speaker can ever in fact produce a sentence with an infinite recursive structure, and in certain cases, people are unable to comprehend sentences with only a few levels of recursion. Chomsky and his supporters have long argued that such cases are best explained by restrictions

27、on working memory, since this provides a principled explanation for limited recursion in language use. Some critics argue that this removes the falsifiability of the premise. Returning to the big picture, it is questionable whether Golds research actually bears on the question of natural language ac

28、quisition at all, since what Gold showed is that there are certain classes of formal languages for which some language in the class cannot be learned given positive evidence alone. Its not at all clear that natural languages fall in such a class, let alone whether they are the ones that are not lear

29、nable.Finally, it has been argued that people may not learn exactly the same grammars as each other. If this is the case, then only a weak version of the third premise is true, as there would be no fully correct grammar to be learned. However, in many cases, Poverty ofStimulus arguments do not in fa

30、ct depend on the assumption that there is only one correct grammar, but rather that there is only one correct class of grammars. For example, the Poverty of Stimulus argument from question formation depends only on the assumption that everyone learns a structure-dependent grammar.4. ConclusionSome e

31、vidence has been presented that child learners have initial preferences in the parameter settings, although this point has been disputed. Several patterns in language have been claimed to be unlearnable from positive evidence alone. There is also much criticism about whether negative evidence is really so rarely encountered by children. Finally, it has been argued that people may not learn exactly the same grammars as each other.ReferencesChomsky, N. (1989) Some notes on economy of derivation and representation, MIT Working Papers in Lin