An Investigation of Dual Task Effect on The Severity of Stuttering in School-Age Children

Objective: Stuttering is a speech disorder that occurs with frequent and abnormal disruptions in speech, such as sound repetition, sound prolongation, and sound or airflow blockage. Although various hypotheses and factors have been introduced including cognitive and linguistic factors, the etiology of stuttering has not been fully understood. According to the vicious circle hypothesis, increased speech disfluency results from hypervigilance to speech. However, this study aimed to measure the effect of reduced attention on speech through verbal and non-verbal dual tasks among school children with stuttering. Furthermore, the effect of dual tasks on the severity of stuttering is investigated among them.  Method: In this cross-sectional study, the participants included 39 children (5 girls 12.8%) and (34 (87.2%) boys) aged 8-12 years (10.25±1.35) with developmental stuttering selected via convenience sampling from primary schools in districts 4 and 8 and speech therapy clinics in Tehran, Iran. Dual tasks were designed using the Visual Basic program. During the research, four speech samples were recorded for each participant. The second and third samples were designed as a dual task (addition of verbal or non-verbal tasks) while the first and fourth samples were designed as a single task. The participant’s severity of stuttering in each sample was calculated based on the number of stuttered syllables (SS%) and data were entered into SPSS-20 software for analysis. Given the non-normal distribution of data, the generalized linear model with the method of generalized estimating equation (GEE) and Bonferroni test were used to determine the difference in stuttering severity among speech samples. Findings: The GEE results showed that the severity of stuttering was different among the four speech samples (P-value = 0.015). The lowest and highest mean stuttering severity among the 39 participants pertained to non-verbal dual task (14.85) and the initial single task (17.11), respectively. A pairwise comparison of stuttering severity showed that the mean stuttering severity in the final single task was significantly lower than the initial single task (P-value<0.05). However, mean stuttering severity was not significantly different between verbal and non-verbal tasks (P-value>0.05). Conclusion: Findings of this study showed that severity of stuttering reduces when children with stuttering perform dual tasks. In other words, focusing children’s attention on verbal and non-verbal tasks while talking led to a reduction in their disfluency.