A series of single-subject experiments evaluated the effects of frequency-altered auditory feedback (FAF) on the speech performance of four adult males who stutter. Using alterations of plus or minus one octave, FAF was compared with normal auditory feedback (NAF) in oral reading and spontaneous speech with measurements made of stuttered intervals, stutter-free speech rate, and speech naturalness. The effects of extended FAF conditions on spontaneous speech were also evaluated for two subjects who demonstrated a positive response to FAF. Results showed no consistencies across subjects in responses to FAF: One subject showed no response, another produced an initial temporary response, a third showed a deterioration in speech quality with minimal reductions in stuttering, and a fourth displayed substantial and sustained improvements in speech performance. Some implications of these findings for current research and theory about the relationship between stuttering and FAF are discussed.

In response to the recognized need for a valid and reliable way to measure stuttering, this study investigates a measurement methodology based on time-interval analyses of stuttering event judgments. Three groups of judges, differing in stuttering judgment experience, identified stuttering events in 12 repeated presentations of five 1-min speech samples. Fixed time intervals ranging from 0.2 sec to 7.0 sec were then superimposed on the event judgments by a data analysis program. Inter- and intrajudge interval-by-interval agreement, and agreement for total numbers of intervals containing stuttering event judgments, were calculated for each judge group. Results showed that agreement was superior among more experienced judges and in longer interval lengths. Agreement varied across speech samples but not across the repeated judgment opportunities. Agreement was maximized at greater than chance levels for an interval of approximately 3.0 sec, but even this best agreement did not exceed a mean of approximately 60% for experienced judges.

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