INTRODUCTION

In the majority of studies of crosslinguistic influence in L2 acquisition, usually only the L1 is taken into account. In the case of a bilingual or polyglot, this may well be an oversimplification of the situation. A previously learned language (referred to here as an L2) may also have an influence on a learner's production in a new target language (referred to here as L3). The aim of the following is to explore similarities and differences in the occurrence of L1 English and L2 German in what we refer to as non-adapted language switches using a case study of the first two years of L3 production in an adult learner of L3 whose background languages are L1 English and L2 German, and to propose a developmental model of L3 production.

The influence of previously learned languages on a learner's production in the target language may show itself not only in the form of crosslinguistic influence on the learner's interlanguage (IL) but also in the non-target-language-adapted (non-TL-adapted) occurrence of non-L3 languages during target language production. Intentional language switching is referred to in the bilingualism literature in terms of code-switching, borrowing or language mixing. In the L2 literature such language switching is referred to largely in terms of communication strategies (Bialystok 1983; Færch and Kasper 1983) used by the learner to overcome problems arising from a limited lexicon.