There is a long and noble history to the study of child language. The earliest recorded study can be traced to Psamtik I of Egypt. These early isolation studies aimed to discover whether infants have a natural tendency to create language and if so what sort of language. The authenticity and veracity of these early experiments is suspect but the original question posed remains alive.

In the late 1950s and early 1960s investigative studies pioneered by Roger Brown and his colleagues led the way in establishing a vibrant research agenda. The field of study now spans a range of disciplines, methodological approaches and very different views on the origins of language. The time has come when researchers and students alike require a comprehensive reference book. The question is whether The Handbook of Child Language can serve this purpose.

Such a handbook must meet several objectives including a detailed and up-to-date account of the patterns of language progression and the processes that drive development. It should also cover the field both in substantive content and in theory as well as identify the main debates, highlighting the continuity of dilemmas across different elements of the language system.

If these aims are met, the handbook becomes both a reference source and a forum for generating the research agenda for the next decade. To what extent does The Handbook of Child Language achieve these high standards?

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Paul Fletcher and Brian MacWhinney have brought together a collection of 26 chapters by leading researchers. Diverse topics span various theoretical positions. The book is organised around three explicit themes: theory, method and context (Part I); the emergence and consolidation of linguistic abilities (Part II); and non-normal language development (Part III). Each part is preceded by a short outline guiding the reader to the central questions and briefly summarising the contributors' chapters. This conventional structure offers a useful frame of reference but it is the implicit themes crossing the chapters that capture the inquisitive mind: the mismatch between comprehension and production; the nature of the child's early representations; the association (or lack of it) between cognition and language; the variation (or lack of it) in patterns; and timing in language development.

Researchers will be familiar with these themes in their own areas of expertise but rarely is there an opportunity to consider their impact across the language system. John Locke, for example, in his chapter suggests that the "grammatical analysis module" is not specific to spoken language but includes manual systems as well.

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Consider, as another example, the mismatch between comprehension and production. It is commonly assumed that children understand more than they can produce, but this simple characterisation fails to capture the complexities that are evident in lexical, syntactical, and phonological development and those that occur in special populations. In a similar vein cross-linguistic studies appear in chapters dealing with normal and non-normal development and in association with different language structures (Ann Peters) and different cultural circumstances (Elinor Ochs and Bambi Schieffelin).

The individual chapters vary in style and there is no standard format to guide the reader: some chapters have numbered sections, others do not; some have conclusions, others have summaries and yet others have neither. Yet with few exceptions they are clearly written and accessible, and the typographical errors and incorrect references are only a minor irritation.

In general, the authors opt for breadth of coverage around a particular topic. The best chapters integrate new findings, develop theoretical frameworks and present a set of research questions that will drive child language research for some years. Part I is dominated by such chapters and the specialist reader will be completely absorbed in the analysis and argument.

The methodology section in Part I is more of a guide to critical questions than advice about particular approaches, though these are addressed elsewhere (Richard Ely and Jean Berko-Gleason).

In Part I Elizabeth Bates and her colleagues put forward a series of interesting theoretical questions resulting from their own studies of language variation. They record enormous variability in each of their measures, variability that, they argue, is due to a combination of factors. They conclude that "theories of language development can no longer rely on the mythical being . . . the average child".

Catherine Snow considers the social and contextual influences on lexical development, syntactical development and the development of communicative intents. Just as Bates et al challenge the existence of the "average child", Snow questions the existence of an unitary phenomenon called child directed speech, CDS. She highlights the importance of considering both its frequency and density.

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Part II describes the child's emerging linguistic skills across the phonological, lexical and syntactical systems. These chapters are separated into those that consider early skills and those that consider skills acquired later. As a whole they serve as a summary of the research findings on normal language skills. The careful reader will note subtle developments in theoretical perspectives. For example, Roberta Golinkoff and Kathy Hirsh-Pasek identify both substantive and methodological questions around children's understanding of sentences. They suggest some "devious and clever ways" of assessing linguistic performance.

Comprehension is considered as a way of building mental models of the world. They proceed to identify three phases a child passes through on the road to constructing complex meanings from the input they receive. Many of the chapters contain new data or theories that warrant further investigation.

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Our research endeavours have replaced the isolation experiments of earlier times with experiments of nature. Studies of special populations have gained considerable momentum as a way of providing answers to some big issues in language development.

Many of the early chapters draw on data from non-normal populations in their discussions but Part III tackles these issues directly. It is also most vulnerable to attack. The introduction provides little rationale for the topics chosen. The absence of chapters on sign language development and language in deaf children is a glaring omission, given the editors' decision to include a special section on patterns of development in non-normal populations.

Fletcher and Richard Ingham's description of grammatical impairment deserves special mention for its breadth of coverage and the incisiveness of its analysis. They detail grammatical impairments in English and across other languages and conclude "it is unlikely that specific language impairment will eventually be seen as a homogeneous disorder with well-defined consequences for the grammar of those it affects". This chapter highlights the complexity of studying special populations and the danger of over-simplistic approaches that ignore the interaction of contributing factors when development is atypical.

The aims of a good handbook have undoubtably been achieved - I have already referred students to it often and the issues raised in its chapters will stimulate many discussions in years to come.

Julie Dockrell is lecturer in child development, Institute of Education, University of London.