Intersyllabic movement timing in the fluent speech of stutterers with different disfluency levels

The goal of this study was to identify possible differences in movement timing in the fluent speech of adult stutterers who show varying levels of speech disfluency. Strain gauge recordings of lip and jaw movements and electroglottographic recordings of laryngeal vibration were obtained in 31 subjects as they repeated simple speech utterances. Measures of the duration and variability of intersyllablic articulatory events were analyzed in relation to speech disfluency level and history of speech treatment. As expected, movement durations were longer in subjects who had been through speech treatment. No significant associations were observed between timing durations and disfluency level. However, more disfluent subjects tended to show reduced variability in timing durations, an effect that was independent of speech treatment. This finding is interpreted in relation to previous observations on control systems that show instability and disfunction in association with reduced output variability. When disfluency level was measured during physiologic testing, duration interacted with speech treatment, with more disfluent subjects in the treatment group showing increased durations in their fluent speech. This effect is attributed to volitional control intended to facilitate speech fluency.