'This book represents a major contribution to the study of both lexical diversity and language development... [and] provides the most comprehensive and compelling study available to date of vocabulary measurement, including type-token ratios, number of different words, and word length. The innovative, empirically validated, and user-friendly measure of lexical diversity (VOCD - or simply "D") that it proposes is based on deep understanding of mathematical models combined with rich background in language acquisition and language assessment. The culmination of fifteen years of cooperative research between David Malvern, Brian Richards, and their co-authors at the University of Reading, this study represents the best of inter-disciplinary research. In style, the book is both erudite and readable. It should be an invaluable source of reference for scholars and graduate-level students in general and psycho-linguistics, in first and second language acquisition, language education, and language pathology.' Ruth A. Berman, Professor Emeritus, Department of Linguistics, Tel Aviv University 'David Malvern and his co-authors have developed a new and very promising approach to the study of lexical diversity and language development. Their statistical method is far more sophisticated than anything we have had in the past. This book will be of great interest to the developmental psycholinguistic community.' Professor Jean Berko Gleason, Department of Psychology, Boston University

Various facets of vocabulary richness, including lexical diversity and use of rare words, have an important role in assessing first and second language proficiency, diagnosing progress and testing theories of language development. There are, however, considerable difficulties in quantifying these variables reliably. This book reviews and evaluates different methods of measuring how vocabulary is deployed in spontaneous speech and writing, before introducing alternative approaches which can assess overall lexical diversity, measure morphological development and compare the development of different word classes. These practical solutions are validated and illustrated by their application to a succession of data sets, including speech and writing, and first and second language. The book also contains a glossary that throws light on the confusing proliferation of measures used in language assessment, sample transcripts, and documentation for a new and more flexible version of the vocd software developed by the authors.

CONTENTS: List of Tables - List of Figures - Acknowledgements - PART I: MEASURING LEXICAL DIVERSITY - Introduction - Some Approaches to Measuring Lexical Diversity - A Mathematical Model of Lexical Diversity - PART II: VALIDATION OF THE MODEL THROUGH ITS APPLICATION TO LANGUAGE CORPORA - Early Child Language 1: The New England Corpus - Early Child Language 2: The Bristol Corpus - Lexical Diversity and the Investigation of Accommodation in Foreign Language Proficiency Interviews - A New Measure of Inflectional Diversity and its Application to English and Spanish Date Sets - PART III: DIFFERENT WORD CATEGORIES AND THEIR DIVERSITY: TYPE-TYPE VERSUS TYPE-TOKEN - Comparing the Diversity of Lexical Categories: The Type/Type Ratio and Related Measures - Lexical Diversity and Lexical Sophistication in First Language Writing - PART IV: CONCLUSION - Overview and Conclusions - Notes - Glossary of Technical Terms and Acronyms - Appendices - Index