Efficacy of the Modifying Phonation Intervals (MPI) Stuttering Treatment Program With Adults Who Stutter

Abstract

Purpose: This study compared a new adult stuttering treatment program (Modifying Phonation Intervals, or MPI) with the standard of care for reducing stuttered speech in adults (prolonged speech).

Method: Twenty-seven adults who stutter were assigned to either MPI or prolonged speech treatment, both of which used similar infrastructures. Speech and related variables were assessed in 3 within-clinic and 3 beyond-clinic speaking situations for participants who successfully completed all treatment phases.

Results: At transfer, maintenance, and follow-up, the speech of 14 participants who successfully completed treatment was similar to that of normally fluent adults. Successful participants also showed increased self-identification as a "normal speaker," decreased self-identification as a "stutterer," reduced short intervals of phonation, and some increased use of longer duration phonation intervals. Eleven successful participants received the MPI treatment, and 3 received the prolonged speech treatment.

Conclusions: Outcomes for successful participants were very similar for the 2 treatments. The much larger proportion of successful participants in the MPI group, however, combined with the predictive value of specific changes in PI durations suggest that MPI treatment was relatively more effective at assisting clients to identify and change the specific speech behaviors that are associated with successful treatment of stuttered speech in adults.

Figure 1.

This figure illustrates (a) how the MPI program collects phonated intervals; (b) how the entire corpus of PIs is then ranked from the longest to the shortest duration PI; (c) how the target range is identified by locating the bottom 20th percentile or quintile range of the ranked distribution; and (d) how PIs that occur within the TRPI range (now shown in red) are identified in real time (i.e., during speech) with an audible and visual stimulus being immediately transmitted to the speaker. MPI = Modified Phonation Intervals treatment; PI = phonation interval.

Figure 2.

Mean and range of %SS, SFSPM, and NAT scores from each TEST assessment for successful participants who completed MPI (left) or prolonged speech (PS, right). %SS = percent syllables stuttered; SFSPM = syllables per minute in stutter-free speech; NAT = speech naturalness; TEST = Treatment Evaluation Speaking Tasks (Ingham et al., 2001); MPI = Modifying Phonation Intervals treatment.

Figure 3.

Mean %SS, SFSPM, and NAT scores from TEST assessments (cf. Figure 2), shown separately for three within-clinic speaking tasks (orange = READ; blue = MONO; black = PHONE) and three beyond-clinic speaking tasks (green = PHONE; blue = CONV (family); red = SELF-SEL). %SS = percent syllables stuttered; SFSPM = syllables per minute in stutter-free speech; NAT = speech naturalness; TEST = Treatment Evaluation Speaking Tasks (Ingham et al., 2001); MPI = Modifying Phonation Intervals treatment.

Figure 4.

Mean (and 95% confidence limits) number of PIs per minute within the duration ranges that defined the quintiles individually derived for each speaker from pretreatment speech, shown for participants who successfully completed their treatment program (black), participants who did not (red), and controls (green), for within-clinic TEST assessments in READ, MONO, and PHONE conditions at the end of pretreatment (PT), the middle and end of establishment (E1, E2), and the middle and end of transfer (T1, T2). PI = phonation interval; TEST = Treatment Evaluation Speaking Tasks (Ingham et al., 2001); MPI = Modifying Phonation Intervals treatment; READ = reading from a novel; MONO = monologue on a self-chosen topic; PHONE = telephone conversation.

Figure 5.

Results of comparisons between participants who successfully completed their treatment program and those who did not, for measures of the number of phonation intervals (PIs) per minute within the duration ranges derived by quintile from pretreatment speech (cf. Figure 4). Significant Student t tests for differences between the groups' means, where p ≤ .05, are labeled M; significant F tests for differences in the variance, where p ≤ .05, are labeled V. Student t tests were used to compare means between the two groups, and an F test was used to compare variances between two groups. A quantile-quantile plot or normal probability plot was used to check the normality assumption (Wilk & Gnanadesikan, 1968). Wilcoxon rank sum test was also applied, and the results remained the same. READ = reading from a novel; MONO = monologue on a self-chosen topic; PHONE = telephone conversation.