Although the book's original organization has been retained, the material in each chapter has been thoroughly updated and revised. Nearly 1,000 new studies have been cited since the seventh edition alone - studies that my research assistants and I culled from the several thousand we reviewed to prepare for this edition. We work from a list of about fifty scientific journals from the fields of psychology, education, sociology, psychiatry, economics, law, neuroscience, medicine, history, and anthropology, and my assistants and I review the abstract of every single article involving adolescents published since the last edition of the textbook. If the abstract looks interesting, I read the entire article and decide whether it contains information that students need to know.

Like the field of adolescence itself, some things about this book have changed very little over the years, and others have been completely transformed. In addition to the increase in our knowledge about adolescents from different cultural groups and different parts of the world, which, as noted earlier, pervades every chapter, our understanding of adolescent brain development, sleep, risk-taking, romance, religious development, conduct disorder, and media use (including use of the Internet) expanded substantially since the last edition, as has our knowledge about neighborhood influences on development and the prolonged extension of late adolescence (what some writers have called "emerging adulthood"), and sections on these topics have been either added or completely rewritten.

This edition of Adolescence drops a feature that ran throughout the last several editions. In those editions, a box entitled "The Scientific Study of Adolescence" in each chapter examined one particular study in detail. In consulting with many users of the last edition, I came to the conclusion that it was unwise to include any important material in a boxed insert, because instructors told me that students often skipped over these. In this edition, I've moved the most important content that had been contained in these boxes into the text. I've retained the use of interim summaries - called "re-caps" - and thought-provoking questions - called "Food for Thought" - based on the positive feedback I've received from users. I've learned that some instructors use the "Food for Thought" questions to launch class discussions or as essay questions on examinations.

I also worked especially hard to make the writing more accessible. Some reviewers noted that, with the addition of more and more research with each edition - an addition that was necessary because of the expansion of scientific knowledge - the text had become a little encyclopedic. I've fixed that in this edition and have added more subheadings to help guide students through each chapter. We've also opened up the design of the book and given the pages a new, fresh look.