Masters Theses

Date of Award

12-2005

Degree Type

Thesis

Degree Name

Master of Arts

Major

Speech Pathology

Major Professor

Tim Saltuklaroglu

Committee Members

Dr. Maria Muñoz, Dr. Mark Hedrick

Abstract

The present study investigated the possibility of finding and quantifying correlates of stuttering behaviors outside of the speech production system. One female and six male adults who stutter (aged 22-49) drew continuous circles on a digital x-y pad under seven conditions: 1) while silent, 2) while reading alone, 3) while reading under choral speech, 4) while reading under frequency altered feedback (FAF) shifted up one-half octave, 5) while reading under FAF shifted down one-half octave, 6) while reading under delayed auditory feedback (DAF) of 100 milliseconds (ms), and 7) while reading under DAF of 200ms. Normalized jerk (NJ), a measure of motor disfluency, was measured during the drawing tasks. In addition, the proportion of stuttered syllables was computed for all reading tasks. Seven age and gender matched non-stuttering participants were also tested to examine group differences in NJ measures. Participants in the stuttering group displayed higer levels of mean NJ than controls in all reading conditions, but not for the silent condition. For the stuttering group, mean NJ measures were lowest in the silent (non-reading task), and showed a 49% increase for the unassisted (solo) reading condition. In terms of stuttering frequency, solo reading, the condition in which NJ measures were the highest, was also the condition which produced the highest mean proportion of stuttered syllables (0.13). During the choral condition, in which stuttering was reduced by 95% to its lowest level (0.01), the NJ measures were reduced by approximately 20%, more than any other reading task. The FAF and DAF conditions resulted in 58-75% decreases in stuttering frequency, and NJ values that were lower than solo reading, but higher than the choral condition. For the control subjects, the mean NJ values remained relatively stable across conditions. In conclusion, for the stuttering group, under conditions in which stuttering frequency was high, NJ measures were high, and under fluency-enhancing conditions which lowered the stuttering frequency, NJ measures also decreased. Thus, it appears that stuttering can produce quantifiable disfluent effects on motor systems beyond the speech motor system and that reductions in overt stuttering are related to reductions in measures of normalized jerk.

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