[PS-2.22] Use of infant-directed special vocabulary fosters word learning

Haryu, E.

University of Tokyo

When talking to infants, not a few Japanese adults use infant-directed special vocabulary (IDV), onomatopoetic words (e.g., wanwan ?bowwow? for inu ?dog?) or reduplications (e.g., kuQku for kutsu ?shoe?), instead of regular adult forms. The present study aimed to reveal developmental trajectory of caregivers? use of IDV words and its relationship to their infants? word learning. Study 1, a cross-sectional survey assessing mothers whose children were 6, 10, 12, 15, and 18 months old, demonstrated that mothers of 15- and 18-month-olds used more IDV words than those of 6- to 12-month-olds. In Study 2, mothers? use of IDV words was assessed longitudinally when their children were 6, 10, 12, 15, 18, 21, and 24 months old. Their children?s vocabularies at 24 months were also assessed. The results showed that some mothers used a very small number of IDV words, which did not change through the study period. Others changed the number of IDV words they use as their children grew up. The wider the change of a mother?s use of IDV, the more words her child produced at 24 months. The results thus suggested that fine-tuned use of IDV words fosters children?s word learning.