At age five, Sophie begins to appreciate the purpose of the notebooks in which her parents have been writing down utterances produced by herself and her siblings. In expressing her new-found interest in her own language, Sophie reveals that her English is in a period of transition between the Cantonese form of relative clause (preceding the noun, as in [just now I say] that one) and the English one (as in all that I say). During this transitional period she also produces hybrid forms such as that I write that one (section 6.3.2). As discussed in chapter 6, it is only thanks to the diary data that we are able to document this transition.

In this chapter we first survey some methodological issues in the field of early bilingual acquisition at large (section 3.1). We then discuss the methods of data collection, background of the bilingual children, and types of data that form the basis for our investigation of the bilingual child (section 3.2). Finally, we discuss measures of language dominance: we motivate the measurement of dominance using MLU differentials (section 3.3) and discuss the relationship of language preferences, silent periods and code-mixing to language dominance (section 3.4).