Ellen Bialystok and Kenji Hakuta view second-language acquisition as one way of coming to grips with the fundamental nature of language, mind, and brain. Although they have conducted some of the key research in the area of second-language acquisition, they also work more broadly in the fields of cognitive and language development as well as in education policy, and thus they are ideally suited to address this issue.

Using an array of vivid illustrations, lively anecdotes, and fascinating research examples, they show how five elements - brain, language, mind, self, and culture - make up the complex ecology of language learning.

The book considers vital questions: Is the brain "hard-wired" for language learning? Why are the mental operations that allow us to learn language different from those we use to solve math problems or play a musical instrument? How do differences between languages affect language learning? What are various cultures doing to encourage bilingualism?