The frequency of disfluencies during phonatory transitions in stuttered and nonstuttered speech

The hypothesis that stuttering and nonstuttering adults have fewer disfluencies during voiced-voiced phoneme-to-phoneme phonatory transitions than during voiced-voiceless, voiceless-voiced, or voiceless-voiceless transitions was investigated. The speech of 11 adult stutterers and a matched group of nonstutterers was analyzed according to the occurence of disfluencies during the above categories of phonatory transitions. Each subject's speech was recorded individually while reading several passages. The percentage of disfluencies varied significantly (p < 0.001) across the four phonatory transition categories for both groups of subjects. Both stutterers and nonstutterers demonstrated a lower percentage of disfluencies during voiced-voiced transitions than during voiced-voiceless, voiceless-voiced, and voiceless-voiceless phonatory transitions. Furthermore, both groups of subjects demonstrated a similar distribution of disfluencies across the four phonatory transition categories. An inability to successfully complete phoneme-to-phoneme phonatory transitions does not appear to fully explain the pattern of disfluencies for stuttering or nonstuttering adults.