When both or all participants in a conversation understand both languages, switching has a purpose. It’s almost as if a third language is introduced. Code-switching may occur in large blocks of speech, between sentences or within sentences.
Some authors have made a distinction between language mixing and code-switching. Language mixing has been used to refer to early bilingual infants who sometimes seem (on the surface) to use either language indiscriminately. Code-switching was then used to refer to bilinguals who had separated their two languages. Many authors now feel that a distinction between mixing and code-switching is not sensible or real.
Monolinguals who hear bilinguals code-switch may believe that it shows a deficit, or a lack of competence in both languages. Bilinguals themselves may be anxious or apologetic about their code-switching and attribute it to sloppy language habits. Few bilinguals keep their two languages completely separate. Few bilinguals speak both their languages with native speaker fluency. One language may influence the other, and sometimes the bilingual’s dominant language influences his or her less dominant language. However, code-switching is a valuable and purposeful communication strategy. It does not happen at random. There is usually considerable reason and logic in changing languages. Children tend to code-switch only when they are talking to people who understand both languages. Also, children soon become aware if code-switching is acceptable or not with different people. That is, bilinguals quickly learn to recognize those social situations and those people with whom they can and cannot code-switch.
Familiarity, projected status and the ethos of the context as well as the perceived linguistic skills of the listeners affect the nature and process of code-switching. This suggests that code-switching is not just linguistic; it indicates important social and power relationships.
Above excerpt from the new third edition of A Parents’ and Teachers’ Guide, by Colin Baker, pp. 57-58. Published by Multilingual Matters, 2007.