Janet Werker is internationally acclaimed for her pioneering work on the precursors to language acquisition. She discovered that young infants discriminate sounds from across the world's languages, but by ten to twelve months of age can discriminate easily only sounds that are used to contrast meaning in their own language. More recently, her work has revealed that only after infants become accomplished word learners can they utilize the language-specific categories established in infancy. These discoveries have radically changed the field by highlighting the dynamic, epigenetic relation between perception and language.