Prolonged speech and modification of stuttering: perceptual, acoustic, and electroglottographic data

Prolonged speech and its variants are a group of novel speech patterns that form the basis of a popular treatment for stuttering (Ingham, 1984). It is difficult to determine which features of prolonged speech are necessary for the elimination of stuttered speech because the speech pattern produces simultaneous changes in respiratory, laryngeal, and articulatory activity. Experimental studies have shown that the modification of phonation and of speech rate contributes to stuttering reduction, and increased duration of speech segments and reduced variability of vowel duration are known to occur as a result of prolonged-speech treatment programs. However, previous studies of prolonged speech have all instructed subjects to modify their customary speech patterns in a particular way. The aim of the present study was to investigate changes in the speech pattern of individual subjects when stuttering was modified with prolonged speech without specific instruction in how this should be done. In one experimental phase, 3 subjects showed clinically significant stuttering reductions when instructed to use whichever features of prolonged speech they needed to reduce their stuttering. The resulting perceptually stutter-free speech was judged to be natural sounding. Stuttering in a fourth subject reduced without experimental intervention. Recordings of acoustic and electroglottographic signals from the 4 subjects were analyzed. Changes in the variability of vowel duration occurred in all subjects. Theoretical and clinical implications of the results are discussed.