If you are interested at all in language, read this book. It is gracefully written, with wit, humour and a deceptively down-to-earth sense for incisive examples. Ellen Bialystok and Kenji Hakuta tell the story of a forbidding body of research in an accessible and imaginative style. Their synthesis of research from linguistics, brain science, philosophy, anthropology and psychology produces insights to be found in almost none of these disciplines alone, and for this scholars and general readers alike are in their debt. The same two audiences are likewise well served by the book's honest confronting of two adamantine facts about learning a language one did not grow up in: complexity and particularity. No small part of the complexity of the phenomenon follows from individual differences, and the account of how this is so provides a bracing innoculation against the more one-dimensional "panaceas" from which the field has suffered of late.

The introduction proposes that "language learning takes place in a complex ecology, not in a laboratory. The full repertoire of our human nature, ranging from our cognitive machinery to our social and communicative needs, is engaged in the activity", and the authors promise to "examine five of the channels that (they) believe jointly comprise the ecosystem of language learning, namely brain, language, mind, self, and culture". While keeping their promise and considering evidence from each of these domains, the authors wisely caution that "the danger in considering the different perspectives in isolation is the temptation to yield to simple-minded fads that appear to explain one of these components without considering its possible connections to the others".

As they take up hypotheses and arguments in the five domains of their inquiry, the authors manage to communicate the gist of several issues that are complicated, somewhat technical, or both. For example, the evidence demonstrating that people distinguish speech sounds categorically (not along continua but, so to speak, as discrete quanta) is presented with a lucid, even entertaining, account of our perceptual dependence on voice onset time.

Readers are guided through a peeling away of the many-layered methodological problems in experiments that attempt to test language ability, in particular when individuals of different ages are compared. This gives a renewed appreciation for the importance of a researcher's interpretive skills in reading data and, ultimately, in framing and solving problems.

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The chapter entitled "Mind" takes up the question of how words and meanings come together for individuals. While noting that "ultimately, an almost aesthetic decision regarding the choice of metaphor accounts for some of the most diverse explanations of intelligence, thought and language", the authors go on to state their view "that language acquisition depends on a highly specialized mental module that picks out structure and meaning from heard language and treats it as knowledge". They also acknowledge, however, that while "language learning may well depend on innate knowledge that emerges in an assured and universal sequence . . . it is probably equally necessary that the infant's cognitive development proceed in a timely and judicious fashion. General principles of cognition compromise part of the foundation on which complex meaning and language must rest." The chapter on "Culture" enlists the help of Wittgenstein, Vygotsky, Bruner and Bakhtin in explaining how a self, including that self's language capacity, is grown in social interaction.

One reductive concept escapes Hakuta's and Bialystok's deconstructive wedge: innateness. Granted the unanalysed construct is wielded by so many of the researchers reported here that it would not be fair to take the messengers to task. But since other claims are dissected and their overgeneralisations exposed, it is curious that the authors do not give innateness the same hard look. Had they done so, we might have had a fuller picture of the complexity of the various contexts and phenomena packed into this term - an organism, its convolution with an environment, the chemical, temporal, and even geometric dimensions of genetic expression in ontogeny, not to mention all that remains unknown about the "innate".

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Taking innateness as a conclusion rather than as another opening makes a difference, for example, when a theory is proposed "based on the idea that language is ultimately a system of knowledge that is represented in the mind. These representations are the basis of language performance". A challenge is laid down: "until a theory of language acquisition describes the evolution of the mental representations for language, none of them has explained how people learn a second language". In taking up this challenge, however, there can be no avoiding an examination of what it means, in biological terms, to be innate. More specifically, if certain abstract principles of syntax are somehow innate, how did they get that way? If "representations in the mind" are at the heart of human language, how do they develop in real time, in real brains? Gerald Edelman's or Michael Merzenich's research in neurological development seems relevant in this regard. Unless questions of this kind are confronted, we are left with another list, not an explanation.

In closing, the authors suggest that better and more bidirectional communication between practitioners and researchers should benefit the field immeasurably, since "there is nothing so theoretical as good practice" (David Hunt). This book will no doubt encourage many to do just that.

Charles J. Quinn, Jr is associate professor, department of East Asian languages and literature, Ohio State University.