5.3 Implications of the Reappraisal    19
Bibliography    20
 1 Introduction
Language acquisition refers to a child’s acquisition of his mother tongue. Most children acquire the language quickly and effortlessly. Attempts to explain the effective language acquisition of children have led to the development of the Critical Period Hypothesis (CPH) (Dai & He, 2010: 140).

There is a specific and limited time period for language acquisition that poses a lively debate in the language acquisition area since the launching of CPH by Lenneberg (1967). Such a controversial notion has attracted many researchers’ attention to conduct research from various points of view in both first and second language acquisition in order to support or refute the existence of the age factor and the critical period in language acquisition.     

“Educational linguistics” was a term modeled on educational psychology and educational sociology. It is a problem-oriented discipline, focusing on the needs of practice and drawing from available theories and principles of relevant fields including many subfields of linguistics (Hornberger, 2001). Since EL has the problem-oriented, trans-disciplinary and human-centered nature, it pays much attention to the non-biological factors rather than searching for the explicit age critical period of child language learning.

Because of the immature integrated theoretical systems covering both educational theories and those of second language acquisition, there has been little research on CPH based on a broad view of the educational environment. A reappraisal of the CPH in a wider perspective seems of great necessity. This dissertation holds that: to take a view from Educational Linguistics based on the thorough review and description of CPH, the paper searches the main controversies of the hypothesis, and carefully annotates the precondition of CPH from the theory-practice features of EL: The significance of educational cultural factors. After analyzing the social educational elements about CPH, the paper presents the statement that: the trans-disciplinary features and the focus on social cultural factors make EL a suitable field for more rational and scientific explanations of CPH, as well as for providing new dynamic knowledge and implication in the world of child language acquisition, second language acquisition and foreign language teaching.

2 Literature Review
Since the proposal of Critical Period Hypothesis in 1959, a great many scholars have contributed to researching and testing this hypothesis. Meanwhile, with the appearance of Educational Linguistics 30 years ago, considerably valuable theories and thoughts left by linguists and educators are worthy reviewing.

2.1 Critical Period Hypothesis  
The facts of adult second language acquisition (SLA) contrast sharply with those of first language acquisition (FLA). Whereas the attainment of full linguistic competence is the birthright of all normal children, adults vary widely in their ultimate level of attainment, and linguistic competence comparable to that of natives is seldom attested. A reasonable explanation for the facts of FLA and SLA is given by the Critical Period Hypothesis (CPH). In its most succinct and theory-neutral formulation, the CPH states that there is a limited developmental period during which it is possible to acquire a language, be it L1 or L2, to normal, native-like levels. If this window of opportunity passed, the ability to learn a language will decline.

Critical Period Hypothesis was originated from Penfield and Roberts (1959), who explored the neuroscience of language and their review focused on how inpiduals with brain damage evidenced atypical linguistic performance. The hypothesis was developed by Eric Lenneberg (1967) who amassed evidence in support of the view that the first language acquisition is a biologically constrained process, with a specific timetable ending at puberty. Lenneberg speculated about the implications for second language acquisition, nothing that after puberty, second languages are acquired consciously and with great effort, and often not very successfully. 儿童语言习得关键期假说的教育语言学重估(2):http://www.youerw.com/yingyu/lunwen_5978.html