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Purpose: Four measures of children's developing robustness of phonological contrast were compared to see how they correlated with age, vocabulary size, and adult listeners' correctness ratings. Method: Word-initial sibilant fricative productions from eighty-one 2- to 5-year-old children and 20 adults were phonetically transcribed and acoustically analyzed. Four measures of robustness of contrast were calculated for each speaker on the basis of the centroid frequency measured from each fricative token. Productions that were transcribed as correct from different children were then used as stimuli in a perception experiment in which adult listeners rated the goodness of each production. Results: Results showed that the degree of category overlap, quantified as the percentage of a child's productions whose category could be correctly predicted from the output of a mixed-effects logistic regression model, was the measure that correlated best with listeners' goodness judgments. Conclusions: Even when children's productions have been transcribed as correct, adult listeners are sensitive to within-category variation quantified by the child's degree of category overlap. Further research is needed to explore the relationship between the age of a child and adults' sensitivity to different types of within-category variation in children's speech. [ABSTRACT FROM AUTHOR]

A growing body of research has documented effects of phonotactic probability on young children's nonword repetition. This study extends this research in 2 ways. First, it compares nonword repetitions by 40 young children with phonological disorders with those by 40 same-age peers with typical phonological development on a nonword repetition task in which the frequency of embedded diphone sequences was varied. Second, it examines the relationship between the frequency effect in the nonword repetition task and other measures of linguistic ability in these children. Children in both groups repeated low-frequency sequences less accurately than high-frequency sequences. The children with phonological disorders were less accurate overall but showed no larger disadvantage for the low-frequency sequences than their age peers. Across the group, the size of the frequency effect was correlated with vocabulary size, but it was independent of measures of speech perception and articulatory ability. These results support the hypothesis that the production difficulty associated with low-frequency sequences is related primarily to vocabulary growth rather than to developments in articulatory or perceptual ability. By contrast, production problems experienced by children with phonological disorders do not appear to result from difficulties in making abstractions over known lexical items. Instead, they may be associated with difficulties in building representations in the primary sensory and motor domains. [ABSTRACT FROM AUTHOR]

Adults' performance on a variety of tasks suggests that phonological processing of nonwords is grounded in generalizations about sublexical patterns over all known words. A small body of research suggests that children's phonological acquisition is similarly based on generalizations over the lexicon. To test this account, production accuracy and fluency were examined in nonword repetitions by 104 children and 22 adults. Stimuli were 22 pairs of nonwords, in which one nonword contained a low-frequency or unattested two-phoneme sequence and 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 smaller vocabularies showed a larger influence of frequency on accuracy than children with larger vocabularies. Taken together, these results provide support for a model of phonological acquisition in which knowledge of sublexical units emerges from generalizations made over lexical items. [ABSTRACT FROM AUTHOR]

Characterizes knowledge deficits in children with phonological disorders. Components of continuous knowledge representation; Methodology; Results; Discussion .