Second Language Acquisition (SLA) refers to both the study of individuals and groups who learning a language other than their first language, and to the process of learning that language (Saville-Troike 2006). The researches of the key theories of SLA, such as Universal Grammar, Behaviorist theory, Monitor Model, and Acculturation theory have provided language teachers and learners with an abundance of information and brought significant influence on teaching and learning. This essay will first discuss each of those influential theories of SLA, and then talk about the influence of those theories on language teaching and learning in the following sections.

Nativist Theories of SLA

   The nativist theory deals with the biological belief that language is an innate feature of the infant (Larsen-Freeman and Long 1991). This theory asserts that humans are born with the instinct or "innate facility" for acquiring language. Researchers like Noam Chomsky and Stephen Krashen are firm advocates for this theory.

Chomsky’s Universal Grammar

   Chomsky (1968) argues that children are born with an innate ability to learn language, additionally, he proposed the theory of Universal Grammar holds that all humans know without having to learn the target language, for there are certain basic structural rules that govern it (Chomsky 1968). In this view, the L2 acquisition process is seen as very similar to L1 acquisition, and learners do not to be taught grammar in order to acquire the second language. Mitchell and Myles (2004) agreed, stating that children have an innate faculty that instructs them while learning the second language. Moreover, Carnie (2002 p18) argues that “all speakers of human languages share the same basic innate materials for building their language’s grammar”. These arguments all strongly support Chomsky’s Universal Grammar theory.

However, some linguists have a different view on Chomsky’s Universal Grammar. According to the Universal Grammar theory, learners know the grammatical rules of the mother language and can apply those rules in the acquisition of the second language and judge the sentence grammatically.  However, the problem is nobody has ever taught them what is and what is not grammatical. In addition, when learner transfer the grammatical rules from L1 to L2, the outcome of the grammar transfer would be positive or negative, in other words, the L1 grammar may interfere the acquisition of L2 if the parameter settings are different (Saville-Troike 2006). 

Krashen’s Monitor Model (Input Hypothesis)

   Stephen Krashen's Monitor Model (Krashen 1982) is another nativist theory. The Monitor Model is probably the most cited theory of second language acquisition and it includes five central hypotheses, the Acquisition–Learning Hypothesis, the Monitor Hypothesis, the Natural Order Hypothesis, the Affective Filter Hypothesis and the Input Hypothesis (Krashen 1985). This essay will only focus on the most famous one, the Input Hypothesis.

   The Input Hypotheses puts primary importance on the comprehensible input that language learners are exposed to. Krashen asserts that there is only one way for the learners to acquire language, by exposure to comprehensive input (Lightbown and Spada 1999). The Input Hypothesis forms a foundation for the Natural Approach (Krashen and Terrel 1983), which aims to foster naturalistic language acquisition in a classroom for the purpose of better communication. According to Krashen (1985), if the language learners received understandable input, then the grammatical rules (language structure) will naturally acquired. It is easy to learn from Krashen’s views that the Input Hypothesis extremely emphasized unconscious language teaching by adopting a communicative approach, however, it shows decreased importance on conscious and explicit grammar teaching. Many second language researchers have criticized the untestability of Krashen's hypotheses. Swain (2005) states that what would develop parts of the process of second language learning are the output, speaking and writing. It has been known as the output hypothesis in contrast with Krashen’s input hypothesis. As it can be noticed, there is a need for implementing and improving the use of the two skills (speaking and writing), not only focus on the communicative learning.

Influence on language teaching

  Both Chomsky and Krashen’s theories have had a certain degree of impact on the teaching methods and approaches in the language teaching area.

The Universal Grammar view of language learning is consistent with the communicative language teaching (CLT) approach. CLT mainly focus on communication rather than teach learners grammar rules because their advocates both believe that learning will take place if enough natural input is present. Why explicit grammar teaching is not considered as an important part in second language learning? According to Chomsky’s Universal Grammar theory, it is a fact that learners know a set of principles that can be applied to all languages and parameters that vary from one language to another. (Chomsky 1976), for instance, they know how to combine words together to form sentences, and what is more, they also have the ability to judge sentences’ grammaticality.

   However, it is important to know that these two approaches developed indecently of one another. The view of UG of language learning argue that learners first understand how children acquire their mother tongue, and then being applied to L2 acquisition, while CLT being the result of the perceived failure of grammar-translation by teachers. However, there are certain works show the relations between them.

CLT grew out of Krashen and Terrel's second language acquisition theory, the Natural Approach and based on Krashen's Input Hypothesis. It insists comprehensible input which could be further considered as that grammar should be taught inductively (learners figure out the grammatical rules gradually by themselves through using the target language) rather than deductively (teaching the rules explicitly). What is more, Krashen (1985) states, acquisition as the basic process, refer to the unconscious development of the target language system as a result of using the language for real communication. It indicates and stress that language learning comes about through using language communicatively, rather than through practicing language skills.

   Furthermore, from the observation class in Canadian immersion contexts (Swain 1985), the CLT approach has been found inefficient, and likely to promote fluency but not accuracy in second language production, for it largely focus on stimulating the learners’ communicative skills.

In language teaching classroom, when apply the CLT approach in teaching, the teacher should understand that learning language through communication is only an approach in classroom instruction, and it does not mean that language is just learn for communication as the writing skills and speaking accuracy are mainly based on well-established grammar rules. So, whether and when it requires the grammar-based syllabuses to be set out or the explicit grammar instruction is a matter that need take into consideration by teachers when they are preparing their teaching plan.

Behaviorist theory

   There is another prominent theory of SLA need to discuss in this paper, the environmental-oriented theory. The early works was based on the Behaviorism theory which primarily developed by B.F.Skinner and Ivan Pavlov. Behaviorist theory gave birth to a stimulus-response (S-R) theory which sees language as a set of structures and acquisition as a matter of habit formation. According to Skinner (1976), language is a set of behavior (habits) and language acquisition is the process of formation of such behavior.

According to behaviorist theory, ‘the process of formation’ can be comprehended as the process to learn from the ‘patterns’ and ‘structures’ in the language system. As Howatt and Widdowson (2004) believe that language systems consisted of a finite set of 'patterns' which acted as models for the learner to produce the similar sentences. What is more, Skinner (1976) argues that to learn and establish the formation, learners should learn through imitation. Obviously, imitation plays a necessary role and should be highly emphasized through language learning. For example, teacher should teach the students the ‘basic patterns’ which can be considered as models for the production of similarly constructed sentences and then the learners could imitate to learn the target language.

   The behaviorists argue that any kind of internal mechanism should be ignored and the acquisition stimulus can only produced by environment. According to Ellis (1985 p293), ‘Behaviourist learning theory emphasizes environmental factors as opposed to internal mental ones.’ However, Chomsky (1968) states that children do not learn and reproduce sentences, but they are able to create new sentences that they have never learnt before. In other words, they internalise rules rather than strings of words. In this view, it seems that internalization should also be considered as significant process of language learning even though the environmental factors are strongly emphasized.

Influence on Language Teaching and Learning

  From the above discussion, it is obvious that environmental factors are of great significance in second language acquisition. According to the behaviorism and acculturation theory argued above, the teaching methods or approaches associated with behaviorist views of learning can be adopted in language teaching and learning. The Audiolingual Method and Direct method are good examples which based on behaviorist views and acculturation.

   Behaviorism theory of language learning was taken up widely by language teachers, and has influenced the development of the audiolingual teaching method to a large extent. Williams and Burden (1997) points out that language can be seen as a behavior to be taught when applied behaviorism theory. From what have been mentioned above, it is obvious that ‘patterns’ or ‘structured sentence’ are necessary parts in language teaching. In fact, language will acquired gradually by imitation and repetition of the structural patterns.

Shumann’s Acculturation theory

   The acculturation model, developed by Schumann, is based on social and psychological factors. In his view, SLA is the result of acculturation, which he defines as “the social and psychological integration of the learner with the target language group” (Shumann 1986).

The acculturation model argues that learners will be successful in SLA if there are fewer social and psychological distances between them and the speakers of the target language. Trawinski (2005) claims, social and psychological distances determine how much input the learner will be exposed to, and how much input will be converted in to acquisition. According to Schumann (1990), social distance refers to the learner as a member of a social group that is in contact with another social group whose members speak a different language. Psychological distance is the result of various affective factors which concern the learner as an individual (Ellis 1986). For instance, the learners may encounter culture shock and feel confused when using the target language without much confidence. Therefore, to shorten the social and psychological distance in order that improve the language acquisition is the main goal in acculturation model.

   However, Schumann’s acculturation theory is also, not a perfect one. It should be noted that the acculturation model focuses on social and psychological factors and ignore other variables in SLA, such as age of the acquisition and intelligence. Cook (2008) believes that children are better at learning second language than adults. Besides, intelligence is strongly related to certain kinds of second language abilities than others (Lightbown and Spada 1999). The acculturation theory of SLA is also questioned by other researchers. Ellis (1994) claims, according to acculturation theory, social factor are assumed to have a direct impact on second language acquisition, however, they are more likely to have an indirect one.

Influence on Language Teaching and Learning

Culture difference is an important and inevitable factor within the SLA process. The social and cultural factors are at play in the students' lives and they are considered as the barriers in the learning process. Accordingly, teaching culture in acculturation model is of great importance.

As language teachers, they should develop the curriculums that address the importance of social and personal difference in SLA. Menard-Warwick also points out the significance of teaching social and culture difference in second language class. As he states, teachers need to understand the culture difference that result in confusion for students and therefore they should design the pedagogical plan to teach learners directly by making social and personal difference in acquisition of second language  difference and as topics for discussion in class (Menard-Warwick 2005).

Language teachers should take social and psychological factors into consideration in the process of second language teaching. For example, when teaching in a class with target language speakers (e.g. native speakers), the teacher should take the responsibility of encouraging the learners to work together with the target language speakers as often as they can. Moreover, teachers need to learn as much as they can about their students' identities outside the classroom, and draw on those identities in classroom activities to encourage the students to continue their second language learning.

Conclusion

   In general, it is oblivious that not one individual theory on its own can account for all the aspects in the second language acquisition of the learners. Each one has its valid points and shortcomings. The theories of second language acquisition above are not totally independent from one another. Besides, the crossover with language teaching and learning is clear and need to be noticed by linguists and language teachers.  

In the language teaching class, teachers have to take into account that learners are different, for they do not have the same characteristics, personalities, as well as the learning environments. Consequently, they do not all acquire the target language in the same way. Social background and age of the learners could affect the learners' learning abilities.

From my perspective, it is significant for teachers to take most important aspects of each theory into consideration when planning their lessons. However, it is not necessary for the teachers to address all the SLA theories in language teaching. From a certain amount of teaching experience, the teachers will understand and get the best ideas of these SLA theories.

References and Bibliography

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Cook, V. J. & Chomsky, N. (1988). Chomsky's universal grammar: an introduction, Blackwell.

Cook, V. J. (2008). 4th ed, Second language learning and language teaching. London, Hodder Education.

Ellis, R. (1994). The study of second language. Oxford, OUP.

Ellis,R.(1986).Understanding Second Language Acquisition .Oxford, OUP.

Howatt, A.P.R. & Widdowson, H.G. (2004). A history of English language teaching. Oxford, OUP.

Krashen, S. D. (1982). Principles and Practice in Second language acquisition. Oxford, Pergamon Press

Krashen, S. D. and Terrell, T. D. (1983). The natural approach: Language acquisition in the classroom. Hayward, CA: Alemany Press.

Krashen, S. D. (1985). The input hypothesis: Issues and implications. London and New York, Longman

Larse-Freeman, D. & Long, M. H. (1991). An Introduction to Second Language Acquisition Research. Longman.

Lightbown, P. M. and Spada, N. S. (1999). How language are learned. Oxford, OUP.

Menard-Warwick, J. (2005). International trajectories and sociopolitical context: Latina immigrants in adults ESL. TESOL Quarterly, 39(2), 165-185.

Mitchell, R. & Myles, F. (2004). Second language learning theories, London, Arnold.

Swain, M. (2005). The Output Hypothesis: Its History and its Future.[online]. Last accessed 16 Jan at: http://www.celea.org.cn/2007/keynote/ppt/Merrill%20Swain.pdf

Saville-Troike, M. (2006). Introducing second language acquisition. Cambridge, CUP.

Schumann, J.H. (1986).Research on the Acculturation Model for Second Language Acquisition, Journal of Multilingual and Multicultural Development, (7)5, 379-92.

Schumann, J. H. (1990). Extending the scope of the acculturation / pidginization model to include cognition. TESOL Quarterly. 24(4), 667-684.

Trawinski, M. (2005). An outline of second language acquisition theories. Krakow: Academic Pedagogic.

Williams, M. and Burden, R. L. (1997). Psychology for language teachers: a Social Constructivist Approach. Cambridge, CUP.