Seventy-five years after Vygotsky's death, scholarship exploring developmental relations between language and thought continues to be strong. This edited volume compiles contributions from international leaders in the field on the roles of language and private speech (self-talk) in the development of self-regulation and executive functioning in children and adults. New theoretical insights, empirical research, and potential clinical and educational applications of scholarship on private speech are presented. Relevant for undergraduate and graduate students and scholars of psychology, education, linguistics, and cognitive science, this text will be an essential volume for those interested in the interface between language, cognition, and behaviour, and the development of regulatory or cognitive control over behaviour.