  Much rarer than mastery of second language morphology and syntax is  attainment of a native-like accent, something that first language  learners acquire automatically in   childhood.[23]  A child's ability to perceive language-specific sounds begins in  utero, as demonstrated, for instance, by newborns' preference for the sounds of their mother's voice and their parents' language, and by  their ability to discriminate prose passages that they have heard  during the final trimester from novel passages. In the first few  months of life, babies reliably discriminate many different natural  language phonemes, whether or not they occur in what is soon to  become their language. By ages 6 months to 1 year, however, this  sensitivity to unheard phonemes largely disappears, and by age 1,  children tend to make only the phonological distinctions made in the  language(s) they hear around them. For example, Japanese children  lose the ability to discriminate English /r/ and /l/ (Kuhl et al.,  1997b). As adults, people continue to be unable to perceive some  phonetic contrasts not marked by their language, and many fail to  learn how to produce even those second language sounds which they can   distinguish.[24]  For instance, many English speakers of French have great difficulty  in producing the French /y/ (as in tu) and  back-of-the-throat /r/.