This study examines the variation between children in early language development, focussing on their acquisition of the auxiliary verb. Learning auxiliary verbs and the syntactic and pragmatic functions with which they are associated is an essential component in the child’s language development from an early stage. At the same time, children vary extensively in the age and stage at which auxiliaries emerge and also in the style and rate at which subsequent development takes place. Some aspects of this variation have been linked with the quality of interaction with the child’s conversation partners, others with a tendency to acquire language holistically through unanalysed ‘chunks’. Using data drawn both from the Bristol Longitudinal Study of Language Development and from independent case studies conducted in Wales, Dr Richards points to a number of important areas of variation between children, for example in sequence of syntactic development and in the relationship between pragmatic and syntactic factors, and raises a number of important methodological and theoretical issues, such as how to assess the level of unanalytical usage and how to measure real syntactic advance. By analysing relationships between input and auxiliary growth, the study attempts to resolve some of the inconsistencies in the results of previous studies which have included the auxiliary as a measure. The book will be of value to all those interested in language acquisition, whether linguists, psychologists, speech therapists or lecturers in nursery, infant and special education.