Introduction

The simultaneous acquisition of two (or more) “first languages” can be of particular interest for language acquisition studies. By analyzing the development of two linguistic competences in one individual, we may be capable of sorting out more easily to what extent the underlying logic of development is determined by the grammatical system to be acquired, or the particular way of human language processing as opposed to properties of the individual or of the communicative situation. There is, in fact, a steadily increasing amount of research in this area (see McLaughlin, 1984 or Taeschner, 1983 for fairly comprehensive overviews including more recent studies).

Much of this work is largely descriptive in its orientation, and theoretical questions are not always discussed explicitly. One question which is, however, pursued very frequently is whether bilinguals are able to “differentiate their two linguistic systems” (Lindholm and Padilla, 1978:334). (See, for example, Volterra and Taeschner, 1978, Redlinger and Park, 1980, and Vihman, 1982, 1985, and forthcoming, for some recent contributions to this discussion.)

The emerging picture is somewhat flawed by terminological confusions, especially with respect to those concepts underlying the terms “language mixing” and “code-switching”. To avoid problems of this kind, I will use code-switching to describe the bilingual's ability to select the language according to the interlocutor, the situational context, etc.