In the beginning of this book I mentioned that there are a number of common misconceptions about second-language acquisition in children that do not stand up under empirical scrutiny. In concluding, I will look at some of these unproven assertions by way of summarizing what is not known about childhood bilingualism. Once the limits of knowledge have been delineated, I will set down some propositions I feel are warranted on the basis of research on second-language acquisition in childhood.
There are a number of widely held beliefs about second-language acquisition in children that are unsubstantiated. Of course, there is a sense in which no scientific statement is ever definitively proven. Scientific knowledge consists of an accumulation of probabilistic statements, some more likely to be true that others. To say that a scientific statement is proven is merely to say that the evidence to date leads one to the conclusion that the proposition is likely to be true. The propositions I shall examine here, however, although often accepted as proven, seem as likely to be false as true. I shall restrict the discussion to six such statements.
Proposition 1. The young child acquires a language more quickly and easily than an adult because the child is biologically programmed to acquire languages, whereas the adult is not.