This state-of-the-art volume is the first to capture a hybrid discipline that studies the role and linguistic implications of the human mind in language learning and teaching. This Handbook considers individual as well as collective factors in language learners and teachers from an array of new empirical constructs and theoretical perspectives, including implications for practice and “myths, debates, and disagreements” in the field, and points to future directions for research. This collection of stellar contributions is an essential resource for researchers, advanced students, and teachers working in applied linguistics, second language acquisition, psychology, and education.