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166M. Blomgren, A.M. Goberman / Journal of Communication Disorders 41 (2008) 159–178participants were not asked to match these rates. Participants did not orally practice thetarget rates prior to production of the experimental tasks. Prior research (on differentspeakers than reported here) has shown that both stuttering and non-stuttering speakerseffectively alter their speech rate in response to these rate prompts (Blomgren &Goberman, 2003).All instances of stuttering in the four experimental speaking tasks were identifiedfollowing the same criteria as used for the spontaneous speech sample. However, for thephrases, only stuttering on the initial word comprising each of the 45 phrases wastabulated. Using this methodology, a direct comparison was made between the 45words spoken in isolation to the 45 words spoken within the context of a phrase. For thecontrol speakers, no stuttering was expected. In order to verify that the tasks werenot disfluency-provoking for these normally fluent speakers, normal disfluencieswere counted for this group (e.g., whole word repetitions, false starts, interjections,etc.).2.3. ReliabilityIntrajudge reliability for identification of stuttering in the four experimental speakingtasks was examined by re-analyzing the samples from 10 randomly selected participantsfrom each participant group (45% of the total participants). Interjudge reliability wasassessed by having a second ASHA certified speech-language pathologist analyze thespeaking tasks produced by the same 10 participants. Reliability was calculated on anoverall percentage of stuttering for each task.2.3.1. Normally fluent speakersThe standard error of measurement for identification of percent stuttering in theintrajudge reliability comparison of the experimental speech tasks was 0.0%. Forinterjudge reliability, the standard error of measurement for identification of percentstuttering in the experimental speaking tasks was also 0.0%. A Hoyt’s Analysis, whichprovided a correlation measure of the consistency of rater’s judgments, was conducted forboth intrajudge and interjudge comparisons of the experimental speaking tasks. For allmeasures of consistency, a correlation coefficient of r = 1.00 was achieved. The resultsindicated 100% agreement between the intrajudge and interjudge identification of speechdisfluencies in the experimental speaking tasks.2.3.2. Stuttering participantsThe standard error of measurement for identification of stuttering in the intrajudge andinterjudge reliability assessment of the spontaneous speech and experimental speech taskwas 0.9% and 0.8%, respectively. The standard error of measurement for identification ofstuttering in the intrajudge and interjudge reliability assessment of both speaking tasks was1.7% and 0.5%, respectively. A Hoyt’s Analysis was conducted for both the spontaneousspeech task and the experimental speaking tasks. For all measures of consistency, acorrelation coefficient of r = 0.99 was achieved. The results indicated very high intrajudgeand interjudge reliability for identification of speech disfluencies in the experimentalspeaking tasks.
3. ResultsM. Blomgren, A.M. Goberman / Journal of Communication Disorders 41 (2008) 159–178 1673.1. Controlled speaking tasks3.1.1. Non-stuttering speakersThe 22 normally fluent speakers exhibited no disfluency (stuttering or otherwise) in anyof the four experimental speaking tasks. Thus, the group mean disfluencies were 0.0% foreach of the four tasks. Therefore, speech fluency for the control participants was withinnormal limits. These findings clearly indicate that even the alternating rate tasks wererelatively easy for these individuals and did not result in any speech motor breakdown.3.1.2. Stuttering speakersOverall, the mean percentage of words stuttered by the 22 stuttering speakers across thefour tasks was 12.0% (S.D. = 12.8%). This mean percentage of stuttered words across thefour controlled speaking tasks was remarkably close to the mean percentage of stutteredwords on the spontaneous speaking task (12.3%). The mean percentage of stuttered wordson the single words – habitual rate task was 5.5% (S.D. = 8.9%), the single words – variablerate task was 11.0% (S.D. = 9.0%), the initial words of the phrases – habitual rate task was13.5% (S.D. = 14.1%), and the initial words of the phrases – variable rate task was 18.1%(S.D. = 14.4%).A randomized-blocks two factor ANOVA with repeated measures on both factors wasperformed on the group data to determine whether significant differences existed among thefour tasks with respect to the independent variables of length of utterance and speaking rate.In order to stabilize the inherent variance in percentage type data, the percentage of stutteredwords was transformed to arc-sine values before statistical comparisons were conducted.Length of utterance was the first repeated independent variable (with two levels: words andphrases), and speaking rate was the second repeated independent variable (with two levels:stable and variable). The analysis indicated no interaction between length of utterance andspeaking rate [F(1, 21) = 2.45, p = 0.13]. An ANOVA interaction plot is provided in Fig. 2.Significant main effects were identified for length of utterance [F(1, 21) = 20.91, p = 0.0002]and for speech rate complexity [F(1, 21) = 17.11, p = 0.0005]. Participants demonstratedsignificantly more stuttering on the first word of the phrases compared to single words, andmore stuttering in the variable rate tasks compared to the stable rate tasks.3.2. Performance according to severity levelIn order to evaluate participant performance according to severity of stuttering, twostuttering severity groups were identified from the original 22 participants. A median splitwas conducted and a ‘‘less severe group’’ was established using the 11 participants with thelowest percent of stuttering on the spontaneous speaking task (lower half). A ‘‘more severegroup’’ was established using the 11 participants with the highest percent of stuttering onthe spontaneous speaking task (upper half). It is acknowledged that this median splitmethod is somewhat arbitrary, but it does provide maximal power to examine severityeffects within the data. The spontaneous speaking task was used to separate the groupsbecause it involved a natural context and was also closely matched to the four experimental
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