This study examined the speech behavior of Japanese women when interacting with young children. Sixty-one single Japanese-speaking women, ages 18-26, were recorded as they read aloud picture books to a 1-year-old child and as they conversed with another Japanese-speaking adult woman. When their utterances were acoustically compared between the two settings with regard to prosodic features, both the average pitch and pitch excursions exhibited significant increase when interacting with the child in 17 of the 61 women. In 36 of the remaining 44 individuals, none of the parameters showed such changes. Any retrospective attempt to relate these findings to the individuals' preference for picture books, or previous experience with reading, or with being read the books, or with baby-sitting did not successfully account for the individual variability. The only variable that explained such results was whether the individuals had grown up with siblings or as only children, in that if they were only children, the prosodic modification was significantly less likely to occur. (Contains 22 references.) (MDM)