| It has been well demonstrated that choral speech significantly reduces stuttering frequency in adults who stutter (Andrews et al., 1982; Ingham & Packman, 1979; Rami, 2000, 2005). This finding has led to the development of assistive devices in which speakers who stutter enhance their fluency by speaking while hearing their own voice at a slight delay or at higher or lower pitch than normal. The underlying mechanisms for this effect remain unclear, however. The main purpose of the present study was to assess the role of prosodic cues in the choral speech effect. Adult speakers produced sentences under several choral speaking conditions, including ones that featured modifications of prosodic information, namely pitch contour and durational patterning. Effects of these prosodic modifications upon speech fluency, speech rate, sentence production accuracy, and participants' self-ratings of speech naturalness were assessed. Speech production characteristics in the prosody-altered feedback were compared to those in delayed auditory and frequency-altered conditions as well as in a conversational babble condition which lacked clear segmental and prosodic cues. Results showed that the availability and accuracy of prosodic information (i.e., pitch contour, word durational pattern) did not affect the extent to which choral auditory feedback enhances fluency. In addition, it was shown that alterations in duration-based prosodic feedback do not affect speech fluency differently than alterations in pitch-based 9039prosodic feedback do. That is, participants who stutter spoke as fluently while receiving temporally-altered choral feedback as while receiving pitch contour-altered choral feedback. Furthermore, it was shown that participants who stutter spoke as fluently when speaking under prosody-altered choral feedback as when speaking under DAF, FAF, and typical choral speaking conditions. Even though participants who stutter showed more entrainment to choral speech and it appears that they benefit from choral speech than typical speakers do, finally, it was argued that the entrainment does not seem to be the main mechanism in explaining the fluency enhancing effects observed during choral speech. Several alternative hypotheses are proposed, including ones involving auditory cortex activation to explain fluency enhancing effects of participants who stutter. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)... |
