This book is a thorough revision of the highly successful text first published in 1994. The authors retain the multidisciplinary approach that presents research from linguistics, sociology, psychology, and education, in a format designed for use in an introductory course for undergraduate or graduate students. The research is updated throughout and there are new sections and chapters in this second edition as well. New chapters cover child language acquisition (first and second), Universal Grammar, and instructed language learning; new sections address issues, such as what data analysis doesn't show, replication of research findings, interlanguage transfer (multilingual acquisition and transfer), the aspect hypothesis, general nativism, connectionist approaches, and implicit/explicit knowledge. Major updates include nonlanguage influences and the lexicon. The workbook, "Second Language Learning Data Analysis, Second Edition," makes an ideal accompaniment to the text.