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Background and Aim: Asking questions is one of the basic skills for getting information. "What", "Who", "Where", "Why", "How much", "How, etc. are question words frequently used for asking questions. Studies on the sequence of acquisition of question words in English speaking children follow a unique sequence. "What" is the first question word used by these children. We aimed to study whether Persian speaking children follow a unique pattern in the acquisition and use of question words as well.
Case: Two normal Persian speaking children (a boy and a girl) who were sent to the kindergarten of Faculty of Rehabilitation Sciences, Iran University of Medical Sciences by their parents were investigated. Children's spontaneous speech from 12 to 36 months was videotaped, and question words were extracted from phonetic transcription of both children's speech. In order to ask a question, both children initially used rising tone with /m/ or /hum/ before saying the first question word. Two first question words were "what" and "where" in both children's speech samples. Asking about the time with the question word /when/ was not appeared in their speech samples until 36 months. These two Persian speaking children also used Wh-question sequentially.
Conclusion: The result of this study was consistent with the results of other studies on English speaking children.

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Background: Children usually produce their first words when they are 10-15 months old and go through simple to complex speech by passing some stages. One of the criteria for examining development of children's language is mean length of utterance (MLU). The main purpose of this study was calculating mean length of utterance and grammatical morphemes used by Farsi-speaking children during their 12-60^th months of life.
Case: It was a longitudinal descriptive study. Every month during children's 12 to 60^th months of life, 120-minute spontaneous speech samples of two children in kindergarten were videotaped and transcribed. The girl said her first word at the age of 12, and the boy said his first word at the age of 16 months. Combining words and constructing two-word utterances started at 18 and 20^th months of the girl's and the boy's lives respectively. First grammatical morpheme appeared before the 24^th month of children's lives and when mean length of utterance was lower than 2 morphemes. Singular verb suffixes were acquired sooner than the plural ones. Both children started using six subject identifiers of Farsi language before 36^th month of their lives.
Conclusion: The speech development in Farsi-speaking children follows the same pattern as other children, starting from one-word utterances and complicates gradually by increasing the number of words, word combinations and using grammatical morphemes. The important point is that Farsi-speaking children started to use grammatical morphemes when their mean length of utterance was lower than two morphemes.

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Background and Aim: Studies have shown that most children before age 4 are able to comprehend and express wh-question. In the Persian language, a case study has confirmed these results. The aim of this study is to evaluate the ability of 4-6 year olds to comprehend and express wh-question.
Methods: Seventy two 4-6 year-old Persian-speaking children were selected randomly. Wh-words consist of: what, where, who, why, and when. In the part of comprehension subjects answered questions about two pictures, and in the part of expression they asked questions elicited by a speaking puppet about four pictures. Descriptive analysis and student&aposs t-test were used for data analysis.
Results: In comprehension 4-6 year-old children gained the complete score (2) with SD=0 in all wh-words. However, 4-5 year old children gained the score of 1.89 with SD of 0.32 for the word when. In expression, independent t-test showed the maximum score of 3.52 with SD of 0.84 related to questions with who. 5-6 and 4-5 year old subjects had significant differences in questions with what (p=0.005), where (p=0.003), who (p=0.012), and when (p<0.001). Most errors were expressed in question with when.
Conclusion: Subjects of this study had the ability to comprehend and express wh-words. Comprehension of wh-words is easy for 4-6 year-old children they are able to use them in questions, but have some application errors.

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Background and Aim: In the process of assessing the nasalance scores in patient’s speech, it is vital to know about normative data in the speech of normal subjects. The main objective in this study was to obtain normative data on nasalance scores in normal Persian-speaking children aged 3.5 to 6.5 years.

Methods: In this cross-sectional and comparative study, nasalance was measured in the speech of 112 children (55 boys and 57 girls) in Tehran, Iran. After auditory screening and speech assessments, the subjects who get the sufficient criterions entered the study. Speech sample was obtained by imitation and repeating sentences (14 oral and 3 nasal sentences) and mean nasalance score was measured by Nasal view software.

Results: A mean nasalance score of 46.25% was obtained for nasal sentences and a mean score of 43.67% for fricative sentences, 43.41% for affricative sentences and 42.21% for stop sentences. There was higher nasalance scores in girls but the difference was not significant (p=0.201) there was a significant difference in nasalance scores between different age groups in stop (p=0.037), fricative (p=0.036) and nasal sentences (p=0.032).

Conclusion: Findings of this study prepared good statistical data about nasalance scores in normal Persian-speaking children aged 3.5-6.5 years. The study also revealed that nasalance scores can be different in sentences with same manner of articulation and can be affected by presence or absence of nasal consonants and even age.

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Background and Aim: During speech development in normal children, cluster reduction is one of the natural phonological processes. Children begin to produce some consonant clusters from the age of 2 years but ability to produce all consonant clusters continues up to 9. The main objective of this investigation was assessing the ability of Persian-speaking children in production of consonant clusters in mono-syllable CVCC words.

Methods: In this cross-sectional and comparative study, production of 19 clusters with stop, fricative, affricate, nasal, and glide consonants in 38 words were tested in 200 Persian-speaking children at the age of 3 to 6 years in kindergartens of Tehran, Iran. Content validity indexes of 38 words were above 0.80 and Cronbach’s alpha of split half was 0.91.

Results: More than 75% of 3-years-old children were able to produce /xl/, /bz/, /rs/, and /xm/ clusters. Age was positively correlated with correct production scores of words (p=0.001) and was negatively correlated with cluster reduction scores (p=0.001).

Conclusion: Three-years-old normal Persian-speaking children may use cluster reduction in words with consonant clusters but this phonological process decreased by increasing of age so, most of the 6-years-old children could produce consonant clusters correctly. Place of articulation more than manner of articulation affect on correct production of consonant clusters.