This book sets out to examine the evidence for an age factor in language acquisition, the sources of which range from studies of ‘wolf-children’ to research into the mental capacities of the very old. It goes on to explore the various explanations that have been advanced to account for such evidence and the interplay between the age question and the broader theoretical issues. On a more practical note, the last major section of the book looks at the educational ramifications of the age question, with particular regard to formal second language teaching.