12.6.1. Language transfer – interference Language transfer refers to the influence of the mother tongue on the learning of the foreign language. When there are no major differences between L1 and L2, the transfer will be positive, which will make language learning easier. When there are differences, the learner’s L1 knowledge may interfere with learning L2, negative transfer will occur, which is called (mother-tongue) interference. Interference affects all levels of language, such as pronunciation, grammar, lexis, syntax and so on. The errors arise from the mismatch between the grammatical habits of the learners’ mother tongue and the new grammatical patterns that the learners have to acquire in the foreign language. Although mother tongue interference is a very important cause it is not the only one.