This volume, dedicated to language transfer, starts out with state-of-the-art psycholinguistic approaches to language transfer involving studies on psycho-typological transfer, lexical interference and foreign accent. The next chapter on Transfer in Language Learning, Contact, and Change presents new empirical data from several languages (English, German, Russian, French, Italian) on various transfer phenomena ranging from second language acquisition and contact-induced change in word order to cross-linguistic influences in word formation and the lexicon. Transfer in Applied Linguistics scrutinizes, on the one hand, the external sources of language transfer by investigating bilingual resources and the school context, but also by pointing out the differences in academic language in multilingual adolescents. On the other hand, internal sources of language transfer in multilingual classrooms are illuminated. A final chapter directs its focus on methodological issues that arise when more than one language is studied systematically and it offers a solution on causal effects for the investigation of heritage language proficiencies. The chapter also includes studies that exploit more innovative methodologies on L1 identification and clitic acquisition.