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This study explored both universal features and cultural variation in maternal speech. Japanese and American mothers' speech to infants at 6, 12, and 19 months was compared in a cross-sectional study of 60 dyads observed playing with toys at home. Mothers' speech in both cultures shared common characteristics, such as linguistic simplification and frequent repetition, and mothers made similar adjustments in their speech to infants of different ages. American mothers labeled objects more frequently and consistently than did Japanese mothers, while Japanese mothers used objects to engage infants in social routines more often than did American mothers. American infants had larger noun vocabularies than did Japanese infants, according to maternal report. The greater emphasis on object nouns in American mothers' speech is only partially attributable to structural differences between Japanese and English. Cultural differences in interactional style and beliefs about child rearing strongly influence the structure and content of speech to infants.
Fernald et al. (Tue,) studied this question.