Abstract：As is known there are large numbers of studies on Second Language Acquisition. However， Dynamic System Theory is the new trend in Applied Linguistics. It is necessary to probe into this field and see if it has relationship with SLA.

Key words： Dynamic System Theory；Second Language Acquisition

1. Dynamic System Theory

The DST approach is based on terms like engagement and disengagement， synchrony and discord， breakdown and repair in interaction. （De Bot， W.Lowie and M. Verspoor）. Like many complex systems， the outcome of the development over time has no regular patterns because the dynamic interaction with other variables keeps changing over time and results in unpredictable outcomes.

There are four characteristics： nested property， initial state， fossilization and constant change.

2.Application of DST to SLA

2.1 Studies Abroad on the Application of DST to SLA

（1） Application of Initial Condition to SLA

There is a famous study which indicated that phonological awareness is one of the best predictors of reading acquisition in the native language （Stanovich， 1998）. It is claimed that the reason for the lack of phonological awareness may be the related difficulties in a persons childhood. If a person has these phonemic coding difficulties， not only his reading and writing skills are limited but also the development of oral language. （Sparks， Ganschow and Patton， 1995）. Thus this influence can form a chain.

There is the study on the influence of native language literacy on the successful acquisition of a second language. （Dufva and Voeten， 1999）.

（2） Application of Fossilization to SLA

In 1996， Labov put forward the assumption that one possible cause of L2 fossilization is an initial misperception of sounds. In the initial stage of L2 learning， the learner is inclined to store the misperceived sounds and thus they reach an attractor state which they cannot easily get rid of.

This phenomenon is agreed by Larsen-Freeman. She proposed that fossilization is both a cognitive phenomenon and a social phenomenon. She criticized the study focusing on fossilization as an end state in SLA development. She also concludes that “if language is a dynamic system， then variability of performance and indeterminacy of speakers intuitions would naturally follow” （Larsen-Freeman， 2005）.

（3） Application of Variation to SLA

There are many studies on morpheme order. Dulay and Burt in 1974 published the studies on linear development in SLA by investigating the morpheme order. They thought the acquisition of grammatical morpheme order has no relation with the learners L1 background.endprint

However， this assumption suffers criticism. Larsen-Freeman did large numbers of researches. She found that the orders in the reading and writing task are contrary to the assumption put forward by Dulay and Burt. The object of research is the naturally occurring group of low intermediate high school students of English as a Foreign Language. They are required to write a short journal.

Later the researchers began to realize the need to explain the early morpheme order. Brown has pointed that the cause is the syntactic complexity of the grammatical morphemes for first language acquisition； perceptual saliency and phonological complexity. However， Larsen-Freeman argued that the frequency of occurrence in the input may cause the order to change.

（4） Application of Attrition to SLA

Herdina and Jessner in 2002 pointed out that growth and decline are normal phenomena in developing systems； the only difference is that they are in different direction of change according to the impact of internal and external resources.

Hansen（2001） made a research on both L1 and L2 attrition. He showed that language input and language use have great influence on the language maintenance and this finding is also used to account for the automatic decline in language development.

However， Mearas networks are too rudimentary because words are not simply switched on or off. It cannot be compared to the phenomenon in the real lexicon. There are some researches on the language attrition form the perspective of dynamic systems approach. Firstly， it is found that the attrition is nonlinear； secondly， the average pattern shows a gradual decline， the individual case does not show this decline pattern.

There is also the case that some learners show a remarkable maintenance of language skills even though he is exposed to L2 environment over 25 years. Ammerlaan（1997） has showed that there may have a part of the language system. Once it is acquired， it is difficult to loss.

2.2 Studies at Home on the Application of DST to SLA

（1）The article DST and SLA written by Shen Changhong and LvMin published in 2008 in the Foreign Language Research showed the enlightenment of DST to the studies of language development. This article points out the importance of the social dimension and cognitive dimension in SLA. However， this article is just the translation of western articles on DST into Chinese. It only introduces the history and its four aspects of DST.endprint

（2）The article DST and SLD written by Li Lanxia published in Foreign Language Teaching and Research in 2011 give a relatively detailed introduction on the background of DST， its core definition and some related researches from the theoretical and empirical point of view.

（3）There is also the study on the model of SLA. Study on the Model of SLA on the Basis of DST， the Interaction among Environment， Learner and Language written by Dai Yuncai and Wang Tongshun in 2012 tries to build a dynamic model of SLA in Chinese context. It analyzed the function of these three factors in detail and the interacting factors influence SLA. At last， it shows that this model may give a implication to foreign language teaching.

（4） The article the Application of DST to the Studies of SLA， Take the Vocabulary Development as Example written by Zheng Yongyan in 2011 give the definitions of the connectedness， nonlinearity， self-organizing and attractor and sensitive to initial state. Each definition is accompanied by the empirical studies on the development of vocabulary.

作者簡介：趙哲（1988—），女，山西忻州人，碩士研究生，專業(yè)：英語語言學endprint