INTERNAL STRUCTURE OF CONTENT WORDS LEADING TO LIFESPAN DIFFERENCES IN PHONOLOGICAL DIFFICULTY IN STUTTERING.

This study investigated whether frequency of stuttering was affected by factors that specify the phonological difficulty of a sound and whether and how any influences vary across age groups. Analyses were performed separately on content words and function words. The phonological factors examined were: a) Whether the word contained a late emerging consonant (LEC); and b) Whether the word contained a consonant string (CS). Analyses showed that these factors occurred at different rates across the age groups used (children under 12, teenagers between 12 and 18, and adults). A more detailed breakdown was also reported of frequency of usage of LEC and CS over age groups depending on whether and where these factors occurred in the content words; all nine combinations of no LEC, word-initial LEC, non-initial LEC with no CS, word-initial CS, and non-initial CS were examined. Usage of certain of these nine categories varied over age groups. Friedman statistic on the ratio of stuttering (proportion of stuttered words in a particular word class divided by the proportion of words in that particular word class) showed that the frequency of stuttering remained high for adult speakers when CS and LEC both occurred in a word and when they appeared in word-initial position. These findings support a recently proposed theory that accounts for life-span changes in stuttering.