Abstract: Nowadays, research into the influence of learner’s individual differences on their second language learning has been one of the main topics in the second language acquisition (SLA) filed, and the effect of age difference on eventual attainment has always been one of the most controversial issues. This paper tries to explore the influence of learners’ age factor as well as the other factors related to age in second language acquisition. Some of the researches believe that the younger learners with the biological predominance can acquire second language more easily than the older ones. This kindled a controversy over the three hypotheses: the optimal, the critic period, and the sensitive period. This paper based on the Critical Period Hypothesis and the Sensitive Period Hypothesis to compares children with adults studying an second language in a non-linguistic environment from neurological, cognitive and affective aspects aim to make the results acceptable to the most.

Key words: Second Language Acquisition, Critical Period Hypothesis, Age

摘要：学习者的个体差异是外语学习的一个主要问题，而外语学习其实年龄差异对习得成果的影响一直是语言学家关注的焦点，也是最具争议的问题之一。目前国内外的研究也不尽一致，甚至互相矛盾。至于小孩多大年龄开始学外语比较适合，至今没有定论。本文试图探讨在二语习得中，学习者的年龄因素对二语习得的影响。部分学者认为年龄较小的学习者拥有在生理上的优势，因此比年龄较大的学习着更易习得第二语言。这就引起了三种假说。即，最佳年龄，关键期，敏感期。本文以关键期假说为基础，分别从生理，认知和情感等角度对年龄因素进行了研究。力求寻找二语习得的最佳年龄的最终结论被大多数人接受。

关键词：二语习得，关键期假说，年龄因素