The Handbook of Second Language Acquisition presents an integrated discussion of key, and sometimes controversial, issues in second language acquisition research. * Discusses the biological and cognitive underpinnings of SLA, mechanisms, processes, and constraints on SLA, the level of ultimate attainment, research methods, and the status of SLA as a cognitive science. * Includes contributions from twenty-seven of the world's leading scholars. * Provides an invaluable resource for all students and scholars of human cognition, including those in linguistics, psychology, applied linguistics, ESL, foreign languages, and cognitive science.