Investigating L1 transfer is one of the basic principles of foreign language teaching. What else can German speaking pupils make of all the English grammar rules and vocabulary if they do not compare it with their mother tongue in order to understand the foreign language better? How can teachers understand their pupils language errors? Where do the errors come from? Can we track them? What influence do errors and English-German contrastive analyses have on acquiring a second language and the method of teaching? Errors are systematically made by learners most of the time. Teachers can improve...