Stuttering and speech naturalness: audio and audiovisual judgments

Unsophisticated raters, using 9-point interval scales, judged speech naturalness and stuttering severity of recorded stutterer and nonstutterer speech samples. Raters judged separately the audio-only and audiovisual presentations of each sample. For speech naturalness judgments of stutterer samples, raters invariably judged the audiovisual presentation more unnatural than the audio presentation of the same sample; but for the nonstutterer samples, there was no difference between audio and audiovisual naturalness ratings. Stuttering severity ratings did not differ significantly between audio and audiovisual presentations of the same samples. Rater reliability, interrater agreement, and intrarater agreement for speech naturalness judgments were assessed.