【Abstract】Krashens input hypothesis， also known as the monitor model， is one of the most influential hypotheses in the field of second language acquisition. It answers the question that how language acquisition occurs over time. It has great significance on language teaching and learning. So many linguists and educators pay much attention to it.

【Key words】Krashen； input hypothesis； English teaching

1. The Definition of Krashens Input Hypothesis

In input hypothesis， Krashen claims that an important condition for language acquisition to occur is that the acquirers understand input language that is at “l(fā)evel i+1”. “i” represents the previous linguistic competence and extra-linguistic knowledge （such as the context） existed in the learners brain （the current level）， and the hypothesis claims that we move from “i” to “i+1” along the natural order by understanding input that contains “i+1”. The “i+1” represents their next level which is slightly higher than the current level and the “+1” represents new knowledge or language structures that we should be ready to acquire. That is to say， in order to make sure that learners can understand most of the language but still be challenged to improve， the language that learners are exposed to should be suitable， neither too easy nor too difficult.

2. The Advantages of Krashens Input Hypothesis

As the most influential theory， it has great directive function on second language acquisition. Firstly， it proves the conceptions of “l(fā)earning” and “acquisition” which have great significance on second language teaching and learning. Secondly， the hypothesis redefines the relation between native language and second language， and states that native language may not only have negative functions on second language acquisition， but also positive functions. Thirdly， besides the importance of input， Krashen also emphasizes the significance of learners cognitive level， which suit for the principles in psychology and pedagogy. Finally， it also pays attention to learners affective aspects （such as motivation， confidence， anxiety and so on）， which can help to improve teaching and learning.

3. The Disadvantages of Krashens Input Hypothesis

As we know， Krashen stresses the comprehensibility of input and the natural acquisition of language. However， a great number of scholars have pointed out the problems existing in Input Hypothesis. Firstly， the statement that “comprehensible input is the only causative variable in second language acquisition” ignores the learners and their own active engagement in the pursuit of language competence. Secondly， it does not distinguish input and interaction ignoring the function that interaction displays in L2 acquisition. Thirdly， this hypothesis is difficult to prove and it takes the process that language acquisition device modifies learners interlanguage system for granted. Besides， there is no clear definition and explanation of the state “i+1”， and whether the “i+1” formula can apply to all aspects of language including vocabulary and phonology as well as syntax remains unknown.

4. The Comprehensive Evaluation of Krashens Input Hypothesis

All in all， Krashens input hypothesis analyzes the language acquisition process from the cognitive perspective. Though it is one of the most controversial theories and has got some criticisms and doubt， it still has great contribution to the cognition of language input and acquisition. And inspired by Krashens input hypothesis， more and more researchers give further studies on the basic topics about second language acquisition. To be honest， the further researches which derived from the hypothesis are more important than the hypothesis itself. So without ignorance， input hypothesis has great referential meaning on second language learning and teaching.

Conclusion

The same as many second language acquisition theories， Krashens input hypothesis is not perfect. It has been a bone of contention both in the field of education and second language acquisition since it was proposed. But it cant be overlooked that Input hypothesis still has great significance on language learning and teaching.

References：

[1]H.D.Brown.Principles of Language Learning and Teaching. 2002.

[2]胡壯麟.語言學(xué)教程[M].北京大學(xué)出版社，2011.

[3]馮淳林.克拉申語言輸入假說綜述[J].湖北廣播電視大學(xué)學(xué)報，2010，30（8）：99-100.

作者簡介：趙朝（1992.11-），女，漢族，河北寧晉人，西華師范大學(xué)，外國語學(xué)院碩士研究生，研究方向：學(xué)科教學(xué)英語。