AUDITORY-MOTOR INTEGRATION INFLUENCES ON SPEECH MOTOR CONTROL AND FLUENCY: A COMPARISON OF NORMALLY FLUENT SPEAKERS AND PEOPLE WHO STUTTER

The overall purpose of this dissertation was to identify the effects of delayed auditory feedback (DAF) on speech motor stability and speech fluency in normally fluent adults (PWNS) and to compare them with effects on adults who exhibit persistent stuttering. If the auditory processing influences differently the two groups, it might shed light on the basic role of auditory-to-motor integration in speech production. Differences in auditory feedback dependency were also expected between normally fluent individuals who are highly susceptible to DAF and normally fluent individuals who are minimally affected by DAF. Three studies were conducted to (I) subgroup 62 normally fluent males and females based on their responses to DAF during spontaneous conversational speaking and reading tasks, (II) compare responses to DAF between 15 normally fluent adults who showed high stuttering-like disfluencies (SLD) under DAF (High-SLD group), 15 normally fluent adults who showed low SLD under DAF (Low-SLD group), and 15 adults who stutter, and (III) compare the specific effects of DAF on speech motor stability and movement patterns (lower-lip movement) in 11 normally fluent adults versus 11 adults who stutter. Study I revealed that normally fluent participants, as a group, increased the amount of SLD and speech errors (SE), and decreased articulation rate (AR) when speaking under DAF relative to speaking under amplified non-delayed condition (aNAF). Sex had a limited differential effect on other disfluencies (OD) and AR whereas tas