Language addressed to children, or 'Baby Talk', became the subject of research interest thirty years ago. Since then, the linguistic environment of infants and toddlers has been widely studied. Input and Interaction in Language Acquisition is an up-to-date statement of the facts and controversies surrounding 'Baby Talk', its nature and likely effects. With contributions from leading linguists and psychologists, it explores language acquisition in different cultures and family contexts, in typical and atypical learners, and in second and foreign language learners. It is designed as a sequel to the now famous Talking to Children, edited by Catherine Snow and Charles Ferguson, and Professor Snow here provides an introduction, comparing issues of importance in the field today with the previous concerns of researchers.