下载掌阅APP，畅读海量书库
立即打开
When we try to explain why learners acquire a second language in a certain way，we need to consider the external and internal factors which affect the learning of a second language.External factors relate to the environment in which learning takes place.However，the role and the importance of external factors in L2 acquisition remain a controversial issue.Behaviourists regard them as important factors.Mentalists think internal factors are central to acquisition，believing that the Language Acquisition Device（LAD） enables learners to extract“rules” from input.Cognitive theorists， then， emphasize the joint contribution of both external and internal factors in second language acquisition.
One of the external factors is the social environment in which second language learning takes place.Social factors probably have an indirect rather than a direct effect on the learning of an L2.These factors are likely to be mediated by the attitudes held by learners.Social factors shape learners’ attitudes，which，in turn，decide the learning outcomes.This influences the opportunity to hear and speak and the attitudes towards the language.For example，when you respect or are respected by native speakers，you may learn it well.But when you are disliked by or hate native speakers，or when you want to distance yourselffrom native speakers，you may not learn it well.
A second external factor is the input and interaction.Acquisition cannot take place without a learner's access to input in the L2，which may come in spoken or written form.Spoken input may occur in the context of interaction in which a learner talks with somebody else or in the context of non-reciprocal discourse such as listening to radio or watching TV.The kind of input received by a learner in an interactive context may have been adjusted，and this can be found in language addressed to learners，such as foreigner talk and teacher talk，much of which is simplified input.The input received in a non-reciprocal context is the authentic input from the real world.
Unlike external factors，internal factors are not directly observable.They are covert and can only be inferred by studying learner's production and their report of how they learn an L2.A few internal factors to be discussed here include L1 transfer，cognitive mechanism，communication strategies，general world knowledge，and linguistic universals.
L1 transfer implies the important role the mother tongue plays in the acquisition of a second language.Before a learner learns a second language，he has already acquired his mother tongue，which may be considered a source of learning.Beginners draw on their first language when learning an L2.L1 transfer refers to the incorporation offeatures of the L1 into the knowledge systems of the L2 which the learner is trying to construct.The learner uses his previous L1 experience as a means of organizing the second language data.
There are two kinds of transfer：negative and positive.Negative transfer occurs in cases where the L2 differs from the mother tongue，as is also called interference.In contrast，positive transfer occurs in cases where the patterns of the L1 and the L2 are similar.Therefore，it can be said that L1 both facilitates and impedes L2 learning.In order to make predictions about the occurrence of L1 interference，researchers carried out contrastive analyses of the native language and the target language.It was found that transfer errors are more frequent with beginners than with intermediate L2 learners.This is because the beginners have less previous L2 knowledge to draw on in making hypotheses about rules，and might therefore be expected to make more use of their L1 knowledge.
It is，of course，economical and productive for L2 learners to transfer their L1 knowledge to the new task.They do not have to discover everything from zero.L1 provides a rather rich and specific set ofhypotheses which learners can use.For many aspects of the L2，these hypotheses will be confirmed，because of the similarities that languages share.The L2 learner is likely to feel that everything he learns is different from his mother tongue.In fact，there are many ways in which his L1 knowledge can be directly transferred.Negative transfer often results in erroneous utterances.
However，the results of error analysis studies done by researchers（such as Dulay and Burt 1974）showed that transfer did not necessarily take effect even if there were differences between L1 and L2.Also，many errors made by learners seem to reflect intra-lingual processes rather than L1 interference.That is，they were the result of processes based on the learner's existing knowledge of the L2.But this does not affect the interest in studying transfer.More findings have been made.For example，transfer exists in all aspects of language—phonology， syntax， semantics， and pragmatics； transfer may not always manifest itself as errors，but also as avoidance，overuse，and facilitation.It is generally acknowledged that transfer works in complex ways and that it constitutes only one of the processes involved in L2 acquisition.In a word，L1 transfer is used as a learning process and an aid to communication.
Cognitive mechanics refer to the underlying processes which enable humans to acquire，process，store，and retrieve information，as well as solve problems and make decisions．Perception，attention，memory，reasoning are important cognitive mechanics in language learning.We've just noted that learners use L1 as a means of learning.This learning process consists of cognitive mechanisms which enable learners to extract information about the L2 from input and build their own language system—noticing features in the input，comparing these features with those in learners’mental grammars，and integrating new features into their interlanguages.For example，learners may notice that- s indicates plurality，relative pronoun who substitutes human nouns and which ，non-human nouns.
When L2 learners are engaged in communication，they often have communicative intentions which are difficult to express，because the needed linguistic items are absent in their minds.This problem can often be anticipated by the learner in advance，who may be able to avoid communication or modify what he intended to say.If the learner is already engaged in speaking，he must try to find an alternative way of getting the meaning across.Such a way，in either of the above two cases，of coping with the situation is what is called“communication strategy”.William Littlewood （2000） has summarized some communication strategies as follows：
（1）Avoid communicating.Learners may avoid discussing topics when they know that they lack the necessary vocabulary for those topics.This strategy would be more frequent with learners who dislike risks or uncertainty.
（2） Adjust the message.When it is too late to avoid a problem in an on-going communication，learners may decide to alter the meanings they intended to communicate.They may omit some information，make the ideas simple or less precise，or say something slightly different.
（3）Use paraphrase.In order to communicate a meaning，learners may also use a means of paraphrasing what they want to say，such as circumlocution or description.For instance，a learner might say“ I'd better tie myself in ”if he could not recall the word for“ car seat － belt ”.In this way learners develop their ability to use the L2 fluently or compensate for inadequate knowledge when communicating a particular message.This communicative strategy helps learners make effective use of L2 knowledge.A learner may also invent his own term“ picture place ”，if he has not learned the word“ art gallery ”.
（4）Use approximation.Learners may decide to use words which convey the meaning as closely as possible.One may use a less specific word than the intended meaning（“ some fruit ”instead of“ pineapple ”，for example）.
（5）Create new words.To express the desired meaning，a learner may use a new word or phrase，which might be the result of literal translation of a native language word.A German learner of English，who did not know the word for a“ bedside table ”，coined the word“ night-table ”which is a literal translation for the German Nachttisch .
（6）Switch to the native language.Sometimes learners may decide to lift a word from his own native language instead of trying to create a new one with second language material.For example，a Chinese-speaking learner of English produced“ I saw thefilm Hua Pi yesterday afternoon and had a Er Meng last night .”This strategy is most likely to succeed in situations where the hearer knows the speaker's native language.Learners in the classroom situation often use this strategy.
（7） Use non-linguistic resources.Even in our native language，we often use nonlinguistic resources to make our meanings clearer.Gesture，mime，and imitation are often used in daily communications.For example，we don't have to say“ Please put the vacuum cleaner beside the table ”.Instead，we may point and say“ Put it here ， please .” It is believed that L2 speakers can profit more from these non-linguistic means for complementing their linguistic resources.
（8）Seek help.When a communicative breakdown occurs，learners may seek help from outside.They may use a bilingual dictionary.They may rely on the co-operation of the listener by signaling that he is in difficulty directly or indirectly by means of hesitation.
General world knowledge forms the fundamental background upon which the learner depends while learning an L2.Such knowledge helps learners understand L2 input.This is because human beings， whatever nationality they are from and whichever cultural background they possess，have much in common in understanding the outside world.General world knowledge can be conducive to understanding what other people are talking about.
Just as all human beings possess biological properties and cultural properties，they are equipped with knowledge of how language in general works.This general language knowledge is called language universals.According to mentalist theories，people have innate knowledge of language，which takes the form of Language Acquisition Device（LAD）.Within this device stays the knowledge of linguistic universals.People， somehow， know what is grammatically possible and what is grammatically impossible.
There have been two approaches to the study oflinguistic universals in SLA：typological universals and universal grammar（UG）.The former is devoted to discovering structural similarities among languages.For example，it is found that all languages have nouns and verbs，with nouns functioning as subjects and objects of verbs，and verbs expressing tense，aspect，and modality.This universal knowledge of language is helpful in language learning.The latter probes into one language in great depth to search for language universals，for it is believed that language is species-specific，and the universality of language can be studied by looking closely at one's mother tongue.For example，one of the findings of UG，the Phrase Structure Principle，claims that all languages are made up of phrases consisting of a head and a complement，such as the prepositional phrase in the classroom and verbal phrase have breakfast ，within which in and have are head words and the classroom and breakfast are complements.The only difference is that in some languages，the head precedes the complement，while in others，it may come after the head.Such knowledge affects the learning of an L2.