Speech-related reaction times of stutterers and nonstutterers: diagnostic implications.

Speech-related reaction time measures (laryngeal premotor and adjustment time for /a/, labial initiation and physiological voice onset time for /pa/) and fluency-related measures (number of stutterings, number of normal disfluencies, and time needed to complete an oral reading) of 24 stutterers and a like number of nonstutterers were assessed to determine their diagnostic discriminative power. Discriminant analysis showed that stutterers were most effectively differentiated from normally fluent speakers by the total number of stutterings and normal disfluencies during oral reading and by the duration of laryngeal adjustments prior to cued phonation. Factor analysis revealed that the fluency failure and reaction time measures clustered independently for both stutterers and nonstutterers. These findings suggest that both fluency failures and the duration of laryngeal adjustment time are useful diagnostic measures for discriminating stutterers from those who are normally fluent.