bilingual first language acquisition: one system or two?

one of the most controversial and unresolved questions in bilingual first language acquisition (henceforth bfla) is whether bilingual children develop one mixed or two independent linguistic systems. many scholars in the lield of bfla arc in tavor of the one-system hypothesis (leopold 1970; swain and wesche, 1975; volterra and tacschner, j 987; grosjean, 1982; tacschncr, 1983: mclaughlin, 1984: vihman, 1985: arnherg, 1987: saunders, 1988a). in the studies that claim the validity of the one-system hypothesis, language mixing has been interpreted as evidence for the bilingual child's lack of language differentiation at an early age. this position is rejected here on empirical grounds and evidence is provided, instead, in support of the 'two-system hypothesis'. quantitative analyses of the data revealed that only a small proportion of multi-word utterances was mixed and the rest were language specific. results also showed that the subject of the present study demonstrated bilingual awareness and language differentiation through spontaneous translation and code-switching from a very early age.