Motivating the child to speak a minority language is less of an issue in households where it is the only language spoken. The effort to speak a language whose usefulness is limited to the house is far less than the effort (and frustration) of not being able to speak and communicate, both about their basic needs and their emotions. Sociolinguist Annick de Houwer has looked carefully at language outcomes for children in bilingual homes. In 1999, she did a very general study in a national survey of Flemish families in Belgium about how many children in homes where two languages were spoken would also speak two languages. That is where I got the 3 to 1 statistic I reported in my book. Three-quarters of the children were considered bilingual, and one-quarter were not. To me, this gives comfort to parents who are trying to raise children bilingually, that the odds are in their favor that they will be successful.
On the other hand, it also reassures people who tried to raise a bilingual child, only to find that the child rejected the second language, or the parents were disappointed that the child understood the language, but didn’t speak it. Those parents don’t have to feel guilty or deficient. They can see that their experience is not uncommon. (As you learn in my book, there are many, many factors that go into a child’s dual language learning, and not all of them are under the parents’ control.)
Please remember parents: you are doing the best you can to support your child and her needs. Continuing a bilingual household will reinforce her understanding of the languages and allow for stronger communication between everyone in the home.