Stutterers' self-ratings of speech naturalness: assessing effects and reliability

Using single-subject experiments with 3 adult stutterers, this study evaluated the effects of instructions to stutterers to rate and modify how natural their speech sounds on experimenters' ratings of speech naturalness, stuttering frequency, and speaking rate. The study also included an investigation of the reliability of stutterers' and listeners' naturalness ratings. The stutterers were partway through a therapy program using prolonged speech or rate control. Results showed the stutterers could modify their speech so that their naturalness ratings increased or decreased. These changes were independent of stuttering or speaking rate. Experimenter ratings of speech naturalness were unchanged in conditions where stutterers judged their speech to sound more natural, but paralleled the stutterers' ratings when they judged their speech to sound more unnatural. An attempt to see if stutterers differed in their ratings of how natural their speech sounded or felt showed differences for one stutterer. Reratings of randomized session recordings by experimenters and independent judges showed that their ratings were highly reliable. When the same randomized session recordings were rerated by the stutterers (1 and 3 months after the experiment), their judgments of changes in their speech naturalness, which were not found in the experimenters' ratings, remained consistent and reliable.