Analyzing Vocabulary Commonality Index Using Large-scaled Database of Child Language Development

The present study proposed a vocabulary commonality index for child language development to investigate to what extent each child acquires common words during the early stages of lexical development. We used large-scaled, vocabulary-checklist data from Japanese-speaking children (N=1,451) aged 8-48 months to estimate their age of acquisition (AoA) of 2688 words by logistic regression. Then we calculated the vocabulary commonality index for each child with two datasets. The results showed that as their vocabulary size increases, children who have the same vocabulary size tend to produce common words with the same ratio.