Stuttering and speech naturalness.

The present study was concerned with the development and evaluation of a scale of speech naturalness. Speech samples were recorded of the typical speech of 10 stutterers, 10 stutterers speaking without stuttering under 250-ms delayed auditory feedback (DAF), and 10 nonstutterers speaking normally. Using a 9-point scale, 30 unsophisticated listeners judged how natural the speech sounded in each sample. Results indicated that the stutterer samples were judged as sounding significantly more unnatural than the nonstutterer samples, and the DAF stutter-free samples were judged as sounding significantly more unnatural than the nonstutterer samples. The stutterer and DAF stutter-free samples were not judged as sounding significantly different in terms of speech naturalness. Interrater reliability, interrater agreement, and rater consistency for judging speech naturalness were all satisfactory.