Background and Aim: The correlation of stuttering and different linguistic factors is assessed in many studies. The obtained results can pave the way to reach a better understanding of stuttering, as well as finding more appropriate treatments. This study investigates the effect of utterance length on speech dysfluency comparing stuttering Persian(Farsi) -speaking children and nonstuttering ones.
Methods: Ten stuttering and ten nonstuttering Persian-speaking children between 4 and 6 years of age, matched by age and gender where included in this cross-sectional study. All individuals were investigated by ten sets of simple and complex sentences. Morphemes were added one by one to sentences in each set in order to assess the impact of utterance length on dysfluency. Data analysis was performed using SPSS software.
Results: In practicing ten sets of sentences, the speech dysfluency shows significant enhance with increase of utterance length in both stuttering and nonstuttering children (p=0.001). Furthermore, while comparing two groups of simple and complex sentences, significant increase of speech dysfluency was observed by length enhance of utterance, in both stuttering and nonstuttering children (p<0.05). The comparison of stuttering and nonstuttering children showed significant difference between the two groups as well (p=0.001).
Conclusions: The results of this study show that increase in utterance length in both simple and complex sentences lead to increase in dysfluency in stuttering and nonstuttering children. Stuttering children indicated more dysfluency than nonstuttering ones.

Background and Aim: Recently, researchers have increasingly turned to study the relation between stuttering and syntactic complexity. This study investigates the effect of syntactic complexity on the amount of speech dysfluency in stuttering Persian-speaking children and adults in conversational speech. The obtained results can pave the way to a better understanding of stuttering in children and adults, and finding more appropriate treatments.
Methods: In this cross-sectional study, the participants were 15 stuttering adult Persian-speakers, older than 15 years, and 15 stuttering child Persian-speakers of 4-6 years of age. In this study, first a 30 minute sample of the spontaneous speech of the participants was provided. Then the utterances of each person were studied in respect to the amount of dysfluency and syntactic complexity. The obtained information was analyzed using paired samples t-test.
Results: In both groups of stuttering children and adults, there was a significant difference between the amount of dysfluency of simple and complex sentences (p<0.05).
Conclusion: The results of this study showed that an increase in syntactic complexity in conversational speech, increased the amount of dysfluency in stuttering children and adults. Moreover, as a result of increase of syntactic complexity, dysfluency had a greater increase in stuttering children than stuttering adults.