In the eyes of linguists, defining transfer has proved to be a hard job. There could be many controversies of language transfer among scholars. (Odlin, 1989) According to Odlin, language transfer is the influence resulting from similarities and differences between the target language and any other language that has been previously acquired. Additionally, there were a number of scholars who connected language transfer phenomenon to errors. Transfer was considered responsible for error occurrences in cross-linguistic and cross-cultural studies. (Lado,1957; Corder, 1971).Nevertheless, Richards (1971) held the idea that transfer should not bear all the responsibility, but a part of that. Similarly, Jain (1974) pointed out transfer was only one of the sources of error occurrences.

2.2 The Development of the Significance of Language Transfer

In the 1950s, language transfer played an important role in the theories of second language learning as well as in approaches to second language teaching. 

In the 1960s, its importance is weakened with the acceptance of Noam Chomsky’s Universal Grammar. The theory suggests that linguistic ability manifests itself without being taught (see the poverty of the stimulus argument), and that there are properties that all natural human languages share. It is a matter of observation and experimentation to determine precisely what abilities are innate and what properties are shared by all languages. (“Universal Grammar”, n.d.) Some researches virtually deny the existence of language transfer in their enthusiasm for Universalist explanations. 

In recent years, the role of transfer is acknowledged and transfer is seen to interact with a host of other factors in ways not yet fully understood. “It’s for the researchers to work towards a fuller theoretical understanding of how and when learners draw on their L1.” (Ellis, 1994) An important theory dominating the study of L2 learning now is the cognitive theory. It views the process of learning a language as “skill learning” engaging in perception, memory, problem solving, information processing, etc. In the view of cognitive theory, transfer is not “interference” but a cognitive process. The cognitive theory, which views L1 transfer as one of but not exclusive factors interfere with the L2 acquisition, has replaced CAH accounting for L2 acquisition. Selinker (1969) put “language transfer” at the top of his list of the five cognitive processes responsible for fossilization, interacting with other factors. Thus language transfer is now viewed as a resource, which the learner actively draws in interlanguage development.

But some behaviorists such as Lado, Fries, held the idea that native language influence could greatly affected second language acquisition. According to Lado, elements in target language that are similar to his native language will be simple for him, and those elements that are different will be difficult. (Lado, 1957; Odlin, 1989) But in recent studies, researchers find that some errors occur are not due to native language influence but from other source such as transfer of training.