Psychophysical analysis of audiovisual judgments of speech naturalness of nonstutterers and stutterers.

The purpose of this study was to determine through psychophysical comparison of scaling data whether speech naturalness judgments of stutterers and nonstutterers from audiovisual recordings form a prothetic or a metathetic continuum. Comparison of direct magnitude estimation and equal-appearing interval scale data indicated that speech naturalness forms a metathetic continuum when observers judge audiovisual recordings, suggesting that either scaling procedure is valid for the quantification of this dimension. Ease of use, an existing body of comparative data from different clinics, and somewhat better reliability favor the interval scaling procedure.