Input frequency and word truncation in child Japanese: structural and lexical effects

Recent research indicates that the statistical properties of the input have an impact on the prosodic shape of young children's word production. However, it is still not clear whether the effects of input statistics emerge from the frequency of prosodic structures or the frequency of individual lexical items. This issue is investigated in this study by analyzing cases of word truncation spontaneously produced by three Japanese-speaking children (1;5-2;1) and the frequencies of relevant words and prosodic word structures produced by their mothers. A significant correlation was found between children's truncation rates for individual target words and the frequency of the same words in the maternal input, but not between the truncation rates for different prosodic word structures and the frequencies of the corresponding structures in maternal speech. The size and shape of truncated outputs were better explained in terms of their correspondence to the target structures than the frequencies of shorter forms in the input. The results indicate that variation in early word truncation is systematically related at least to the lexical frequency of the target words, and that input frequency has a clearer connection to what truncates than how it truncates.