OKUMURA, Y. 1 , KOBAYASHI, T. 1 , MINAMI, Y. 2 & MORIYAMA, Y. 2
1 NTT Communication Science Laboratories
2 The University of Electro-Communications
When Japanese parents speak to their child, they often use infant-directed speech (IDS) words such as onomatopoeias and sound-symbolic words (e.g., ?bow-wow? for a dog and ?vroom? for a car). Although IDS words are easier for children to learn than adult-directed (ADS) words (Murase, 2010), it remains unclear (1) whether children produce IDS words earlier than ADS words, and (2) how the acquisition of each IDS word is related. To clarify word acquisition mechanism, the present study collected large-scale data on early vocabulary development. Parents of children learning Japanese aged 8 to 48 months (N=1,285) were asked to check whether their child produced each of 2,688 words. From large-scale data, we estimated the age at which 50% of children produced each IDS word by logistic regression. We also calculated the correlation between the acquisition patterns of IDS words. The results showed that children could produce IDS words earlier than ADS words. For example, they can produce ?wanwan? (bow-wow) at 15 months and ?inu? (dog) at 26 months on average. In addition, children tended to acquire semantically related words such as ?mummy? and ?daddy? at the same timing. These findings are discussed in light of learnability and parental input frequency.