<p>This paper conducts an empirical investigation among English foreign language (EFL) learners at a university in China, mainly on their understanding of the passive voice in their native language to verify the existence of backward transfer in their first language (L1) environment and how backward transfer may relate to the learners' proficiency of second language (L2) English and L1 Chinese in the sentence translation task (STT) and discourse task (DT) of Chinese paragraph writing. The study

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... shows that backward transfer does exist at STT or sentence level in L1 environment. Additionally, the Chinese participants at intermediate English proficiency level are likely to experience backward transfer from L2 English to L1 Chinese. Moreover, for EFL learners at the lower and top English proficiency level no obvious signs of backward transfer shown at the sentence level. And all of the EFL participants have not been influenced by L2 English in the Chinese discourse task. The results of this study convey the complexity of backward transfer and its interactions with L1 and L2 proficiency and different tasks.</p>