Internal structure of content words leading to lifespan differences in phonological difficulty in stuttering

This study investigated whether frequency of stuttering was affected by fac tors that specify the phonological difficulty of a sound and whether and ho w any influences vary across age groups. Analyses were performed separately on content words and function words. The phonological factors examined wer e: a) Whether the word contained a late emerging consonant (LEC): and b) Wh ether the word contained a consonant string (CS). Analyses showed that thes e factors occurred at different rates across the age groups used (children under 12, teenagers between 12 and 18, and adults). A more detailed breakdo wn was also reported of frequency of usage of LEC and CS over age groups de pending on whether and where these factors occurred in the content words; a ll nine combinations of no LEG, word-initial LEG, non-initial LEC with no C S, word-initial CS, and non-initial CS were examined. Usage of certain of t hese nine categories varied over age groups. Friedman statistic on the rati o of stuttering (proportion of stuttered words in a particular word class d ivided by the proportion of words in that particular word class) showed tha t 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. (C) 2000 Elsevier Science Inc.