Langefeld, S., Natke, U., Donath, Th., & Kalveram, K. Th. (2001) Influence of public speaking on the control of vowel duration in stuttering and nonstuttering adults - preliminary results. In H. G. Bosshardt, J. S. Yaruss & H. F. M. Peters (Eds.), Fluency Disorders: Theory, Research, Treatment and Self-help. Proceedings of the Third World Congress of Fluency Disorders in Nyborg, Denmark. Nijmegen: Nijmegen University Press, 574-577.

Abstract
Most stuttering adults are less disfluent when they are speaking alone, but most laboratory based research concerning speech motor control is confined to situations without any audience, thus eliminating one of the most prominent factors leading to disfluent speech. In an experiment 8 stuttering and 8 nonstuttering subjects had to utter the test word ['ta:tatas] under delayed and simultaneous auditory feedback (delay interval: 40 msec) in public and non public surroundings. In all conditions a prolongation effect was found, replicating former studies. Furthermore, public speaking conditions seem to lead to a stronger prolongation effect in nonstuttering people compared to stuttering people. This study yields a first indication of the importance of public speaking surroundings in stuttering research.