Brian Richards examines variation in children's early language development, with special emphasis on the auxiliary verb. He identifies significant variation both in the age and in the stage of emergence of auxiliaries, and in the rate, style and sequence of subsequent development. He relates some of these aspects to a tendency to acquire the auxiliary holistically, and others to the quality of interaction with the child's partners in conversation. This book will be valuable to all those interested in language acquisition, whether linguists, psychologists, or speech therapists.