Language transfer as explained before, refers to how speakers or writers apply their knowledge of one language to another language. This effect can be bi-directional, that is, 1) the individual may apply knowledge from their native language (L1) in the acquisition of their second language (forward transfer), or 2) the second language (L2) can bring effect onto the first language (backward transfer). Given that we are exploring the effects of second language on language, we will be focusing our discussion on backward transfer.
Although the research on the influence of second language on first language are far from being extensive, there are still some research done on this topic. Xin (2014) investigated this topic by observing the effect of English causal clause on the Chinese causal clause. Participants chosen for the study had Chinese as their L1 and English as their L2. Basically, causal relations are expressed differently in English (because, as, since, so) and Chinese (因为… 所以…). Furthermore, it is forbidden to use two connectives in English, but this is permitted in Chinese. Findings suggest the existence of backward transfer but only in conditions where participants’ second language proficiency level has yet to reach the “critical threshold”. This phenomenon occurs when individuals try to restructure the linguistic structure of their native language in hope to simplify the learning process and behave more like a native speaker (Ellis, 1985, as cited in Xin, 2014) .
Similar findings of the existence of backward transfer were found in the study done by Mehrabi (2014). In her study, the influence of second language writing ability on first language writing ability was explored. Participants were Persian native speakers with half of them being English majors and the other half studying nursing. All participants were to go through a pretest and posttest procedure with them writing in their first language on a topic given to them. Following which, English major participants were to go through an English course in writing. After passing the course, all participants were then asked to write a passage in their native language again. Findings demonstrate that participants performed similarly in pretest condition but after going through the English course, English major participants wrote better in their native language. This indicates that even though participants only attended a L2 writing course, the knowledge helped them in the development of their L1 skills and writing ability.
Evidently, the acquisition of a second language has effects on one’s first language. In both studies, it is shown that there is language transfer from one’s L2 knowledge and skills to their native language skills.