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Timing of speech activities are under fine control of an adult, so that time intervals between the phonemes in spectra of phonemes are less than l0ms.In stutterers temporal features of speech such as VOT (time interval between the release of the burst of consonant and onset of vocal vibration) are not under careful control of them, so causing symptoms of nonfluency.In this cross-sectional analytical- descriptive survey VOTs of stutterers (30M. 7F) in first & third syllables of 18 words, which started with /PTK/ & /bdg/ consonants are measured.Statistics tests and t-test, repeated measures, multiple range tests and coefficient regression.Findings:1- Mean VOTs of first and third syllables of stutterers in comparison with first and third syllables of nonstutterers are significant (VOTs of stutterers are longer than nonstutterers) (P<.05).2- Mean VOTs of first syllable in comparison with third syllable in stutterers and nonstutterers are significant (VOTs of first /cv/ syllables are longer than third /cv/ syllables) (P<.05).3- There is a significant difference between VOTs of consonants in adjacency of different vowels (P

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Background and Aim: Since knowing the mechanisms which evoke non-fluency is the first step in the treatment of stuttering, and there are very few researches in Persian which consider the role of the linguistic factors behind  stuttering , this study is an attempt to provide answers to some of numerous questions about stuttering by comparing  the stuttered words` type in stuttered children and adults. 
Materials and Methods: In this study stuttered people were divided into 5 age groups as follows: 3-6, 7-9, 10-12, 13-16, and older than 17 years old. Each group had ten participants. Forty-two of the 50 participants were male , and the youngest person was 3 years old and the eldest one was 32 years old. The study method involved recording at least 5 minuets of spontaneous speech of every one who was diagnosed of suffering from stuttering by two speech and language pathologists. The percent of non-fluency on every word&aposs type was determined where a content word was followed or preceded by a function word (Function-Function-Content words and Function-Content words contexts). Then these findings were analyzed by Kruskal-Wallis and Mann-Whitney tests. 
Results:  The results of this study show while function words are dominantly more stuttered than content words in children less than 13 years old in Function-Function-Content words context, we consider more disfluency on content words and second function word by getting old. We consider more stuttering on function words in children less that 13 years old in Function-Content words context too and increased non-fluency on content word by growing up. Results also show meaningful differences between the fifth group and others in the amount of stuttering on second function word in the Function-Function-Content words contexts and also between the first group and the others in amount of non-fluency both on function and content words in Function-Content words context.
Conclusion: people who stutter from Farsispeakers populations exhibit almost differential patterns of disfluency in different ages. Young speakers who stutter are predominantly disfluent on function words. There is an exchange of disfluencies from function to content words as speakers get older. Disfluencies on both function and content words are so rarely in Function-Content words and Function-Function-Content words contents. These findings support the view that stuttering on function words in children is a way of getting time to complete the next content word&aposs plan. These exchange findings are similar to what is found in English and Spanish languages and explained by the EXPLAN model.

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Background and Aim: There are evidences that indicate a relationship between auditory processing disorders and stuttering, and any disorder in the central auditory function can be at least one of the underlying causes of stuttering. Even though, using the most state of the art radiographic technologies, i.e. MRI, no definitive answer has been given in relative to this question. In this research, using Mask-ing Level Difference (MLD) and Synthetic Sentence Identification (SSI) tests, the central auditory function of stutters and normal group was evaluated.
Materials and Methods: In this study was analytic cross-sectional, fifteen male patients with stutter-ing and 15 male normal cases with the age range from 16 to 40 years (average age 26.78 year) were evaluated. SSI-ICM, SSI-CCM and MLD tests were performed. The results were compared in both groups.
Results: Although stutterers mean MLD was less than that of normal group, the different was not significant between stutters and normal group in SSI test in right ear at negative MCRs. There was a significant difference in ICM state, but in CCM state, there was no significant difference between the average score of two groups in various MCRs.
Conclusion: The findings of this research is compatible with those of similar researches about the SSI test and the pattern of results, probably indicates a partial dysfunction of brainstem in some of the stutters.

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Background and Aim: Objective measurement is general and acoustic measurements in particular have become a substantial aspect of stuttering assessment during the last few decades. Measurements do not replace the perceptual judgment, but they allow a more precise diagnosis, provide more evidence for therapeutic interventions, and are useful as feedback for patients in therapy. The purpose of this investigation was to compare some adult male stutterers&apos and nonstutterers&apos acoustic features.
Materials and Methods: Adult male stutterers and nonstutterers participated this case-control  study. Their fluent reading of 20 sentences in Farsi, prolongation of  vowels /a/ and /i/, and rhythmic counting from 1 to 20 were analyed with Dr. Speech software.
Results: There were no significant differences between two groups in fundamental frequency (f₀) and standard deviation of f₀ in three speech samples (vowels /a/ and /i/, reading 20 sentences, and rhythmic counting from 1 to 20). No significant difference were between two groups for jitter and shimmer.
Conclusion: Non significant differences between two groups are somewhat due to investigation of this parameters in fluent speech of stutterers  and nonstutterers.

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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.

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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.

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Background and Aim: Staggered spondaic words (SSW) test examines central auditory nervous system . Some researches show stuttering causes hyperactivity in motor system of the right hemisphere and cerebellum and decreases activity in the left hemisphere. During stuttering also, central auditory processing is decreased . The aim of this study was to compare the Persian staggered spondaic word test results between persistent developmental stutterers and normal subjects.

Methods: Thirty people with persistent developmental stuttering were participants of this cross-sectional descriptive-analytic study, which were aged 11 to 40 years. The control group matched for gender and number with stutters. They were 8 females and 22 males, with the age of 11 to 40 years, without any stuttering history, neurological diseases and auditory disorders.

Results: Stutterers were in normal category in corrected staggered spondaic words test. The mean scores of errors of right compete, right ear, left compete, left ear and total in corrected s taggered spondaic words between control and stuttering group showed significant differences. There was a significant relationship between stuttering and effect, too (p<0.05).

Conclusion: Based on the obtained results of this study, stutterers may have different cortical and sub - cortical brain activity than people who have not stutter . Central auditory processing abilities of stutterers are weaker than normal people.

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Background and Aim: Attention has causal role in speech and language processing. Studies are limited about relation between attention and language development. As a result, the purpose of this study was to investigate the difference shifting attention function in children with developmental stuttering and fluent speech.

Methods: Thirty children who stutter (21 boys and 9 girls) and thirty children who did not stutter (21 boys and 9 girls) were evaluated. Shifting attention function was investigated using Wisconsin card sorting test. The data were analyzed via Kolmogorov-Smirnov, independent t, and Mann-Whitney U-tests.

Results: Between group analysis showed significant differences for all of the indexes in Wisconsin card sorting test . The number of categories completed in children who stutter was significantly less than that control group (p<0.05). But preservative errors, total errors, total tries, time of test performance and try for first pattern in children who stutter was more than in the control group and data differences were significant for all of the indexes (p<0.05).

Conclusion: The findings of this study show that children with and without stuttering are different in shifting attention function and children who stutter have weaker function in shifting attention. The findings were linked to emerging theoretical frameworks of stuttering development and that were taken to suggest a possible role for attention processes in developmental stuttering.