Vocabulary size and phonotactic probability 1 The interaction between vocabulary size and phonotactic probability effects on children’s production accuracy and fluency in novel word repetition

Adult performance on a variety of tasks suggests that phonological processing of nonwords is grounded in generalizations about sublexical patterns over all known words. To test this account of phonological processing, production accuracy and fluency were examined in nonword repetitions by children and adults. Stimuli were 22 pairs of nonwords, in which one contained a low-frequency or unattested two-phoneme sequence while the other contained a high-frequency sequence. For a subset of these nonword pairs, segment durations were measured. The same sound was produced with a longer duration (less fluently) when it appeared in a low-frequency sequence, as compared to a high-frequency sequence. Low-frequency sequences were also repeated with lower accuracy than high-frequency sequences. Moreover, children with larger vocabularies showed a smaller influence of frequency on accuracy than children with smaller vocabularies. These results support the claim that speakers develop a phonological system based on incremental generalizations over the lexicon.