The influence of phonotactic probability and neighborhood density on children's production of newly learned words.

A word learning paradigm was used to teach children novel words that varied in phonotactic probability and neighborhood density. The effects of frequency and density on speech production were examined when phonetic forms were non-referential (i.e., when no referent was attached) and when phonetic forms were referential (i.e., when a referent was attached through fast mapping). Two methods of analysis were included: (1) kinematic variability of speech movement patterning; and (2) measures of segmental accuracy. Results showed that phonotactic frequency influenced the stability of movement patterning whereas neighborhood density influenced phoneme accuracy. Motor learning was observed in both non-referential and referential novel words. Forms with low phonotactic probability and low neighborhood density showed a word learning effect when a referent was assigned during fast mapping. These results elaborate on and specify the nature of interactivity observed across lexical, phonological, and articulatory domains.

Lexical and articulatory interactions in children's language production.

Traditional models of adult language processing and production include two levels of representation: lexical and sublexical. The current study examines the influence of the inclusion of a lexical representation (i.e. a visual referent and/or object function) on the stability of articulation as well as on phonetic accuracy and variability in typically developing children and children with specific language impairment (SLI). A word learning paradigm was developed so that we could compare children's production with and without lexical representation. The variability and accuracy of productions were examined using speech kinematics as well as traditional phonetic accuracy measures. Results showed that phonetic forms with lexical representation were produced with more articulatory stability than phonetic forms without lexical representation. Using more traditional transcription measures, a paired lexical referent generally did not influence segmental accuracy (percent consonant correct and type token ratio). These results suggest that lexical and articulatory levels of representation are not completely independent. Implications for models of language production are discussed.

The breadth of coarticulatory units in children and adults.

PURPOSE: To assess, in children and adults, the breadth of coarticulatory movements associated with a single rounded vowel. METHOD: Upper and lower lip movements were recorded from 8 young adults and 8 children (aged 4-5 years). A single rounded versus unrounded vowel was embedded in the medial position of pairs of 7-word/7-syllable sentences. RESULTS: Both children and adults produced movement trajectories associated with lip rounding that were very broad temporally (i.e., movement duration lasting 45% to 56% of the sentence). Some effects appeared to extend across the entire utterance. There were no differences between children and adults in the extent of the coarticulatory effect. However, children produced relatively variable movements associated with lip rounding. CONCLUSIONS: These data support the hypothesis that, for young children and adults, broad chunks of output have been planned by the onset of implementation of a sentence. This implies that, based on a change in a single phoneme, the motor commands to the muscles are altered for the production of the entire sentence.