Introduction
Concerning the function of language learning in children’s cognitive development, research on the quality of language development during the early years of development is an important step in collecting normative data from 3- to 7-year-old healthy Persian-speaking children. We should have normative data to measure developmental language disorders in clinical linguistic settings.
Linguistic knowledge comprises 5 subsystems: semantics, morphology, phonology, lexicon, and syntax. The linguistic knowledge of children who learn their mother tongue consists of a limited number of rules, but they can comprehend and produce unlimited sentences. Chomsky called this ability of linguistic competence, creativity [1, 2, 3, 4, 5].
However, based on clinical linguistic data, some children cannot learn their mother tongue properly during the early years of their development. Clinical linguistic studies indicate that about 5% to 12% of children up to 7 years old may face some linguistic disorders [7]. However, the etiology and extent of their language disorders during the early years of development are not necessarily the same.
Researchers have reported different variations of developmental language disorders called special language impairment (SLI), but it is still difficult to reach the same theory from various experts. Watkins believed SLI could be identified in socially and emotionally normal children compared to their peers [11]. Some experts have also referred to developmental language disorders (DLD) [12].
Based on diagnostic and statistical manual of mental disorders, 5th edition (DSM-5) guidelines, two types of developmental language disorders are proposed: developmental language production disorders and comprehension language disorders. Both types must be quantified using normative batteries developed for each language [13].
In the past, the lack of developmentally normative batteries to assess language disorders has compelled clinicians to use their general guidelines without any norms to measure early language disorders. Therefore, it is important to develop normative and reliable batteries for each language to measure the efficacy of rehabilitation by comparing the assessment results before and after any intervention [31].
Two clinical linguistic studies at the University of Social Welfare and Rehabilitation Sciences have been based on a developmental language battery developed for Persian in 2001 and 2005 [18]. The previous studies aimed to measure developmental language disorders in Persian children during their early development years. The results of the two previous studies show that language disorders have been reported at different language levels, including mean length of utterance (MLU), number of contents, and function words compared to their age-matched peers. Their listening and visual comprehension speed were also reported to be less than their age-matched peers [19].
Therefore, the major objectives of the present research are to develop a reliable and valid clinical linguistic battery to collect normative data from 3- to 8-year-old healthy Persian-speaking children in 5 major cities which are dominantly Persian speaking. 

Materials and Methods
The present descriptive developmental normative battery was developed in 3 stages. The first version consisted of 9 subtests,180 items, and two illustrative pictures (Table 1).


Initially, the battery was developed after cultural and linguistic adaptations for the Persian language, including different linguistic levels of phonology, morphology, syntax, and pragmatics. The first draft was performed on two hundred 3- to 8-year-old healthy children living in Tehran City, Iran. The aim was to measure the sensitivity of different test tasks for other age groups. The results of this phase indicated that the battery was not sensitive for 8-year-old children. The content validity ratio (CVR) of the first draft of the battery was checked by 3 Persian-speaking clinical linguistic experts and 3 expert speech therapists. The battery and the results were also presented to 20 speech-language pathologists (SLP) in a clinical linguistic workshop. 
In the second stage, based on the results and suggestions of the experts, necessary corrections were made to the test structure and the items of the first version. The results also indicated that the plural morpheme task of the previous version was not sensitive enough. Therefore, it was removed, and a new semantic task (word definition) as a sensitive semantic task used in other developmental language batteries was added. The second version of the battery consisted of 9 subtests with 105 items and two descriptive pictures. This version was used to collect normative data from 200 children. To determine the reliability and validity of the final version, the opinions of 8 speech therapists and linguists were used to evaluate the construct validity, the correlation matrix, and confirmatory factor analysis, and for its validity, the Cronbach α coefficient was calculated.
The final version of the battery was sent to expert speech therapists in 5 selected target group provinces (Tehran, Mazandaran, Fars, Esfahan, and Khorasan) to collect normative data from one thousand and two hundred 3- to 7-year-old typically developed children in available kindergartens and schools. Finally, the collected data for each task item and connected speech samples were processed and analyzed using version 20 SPSS software.

Results
As mentioned, the first draft of the battery was performed using 200 healthy 3- to 8-year-old children in Tehran to measure the sensitivity of different tasks of the test for other age groups. The results indicated that this version was not sensitive for 8-year-old children. The CVR of the first draft of the battery was also checked by 3 Persian-speaking clinical linguistic experts and 3 speech therapists.
The content validity of the test was 0.78, and the test reliability was 0.76. In addition to confirming the test’s construct and diagnostic validity, the correlation between the subtests and the overall test scores was also significant at 0.01 (with a correlation of 0.20 to 0.83).
The validity coefficient of the subtests is given in Table 2.


The Correlation of the subtests of the structure of the battery is given in Table 3.


In Table 3, the correlation coefficient for 3 to 7 years old children is significant at 0.01. This index Indicates that the relationship between the subtests is significant. 
Factor analysis of the sub-tests is also given in Table 4.


The results of the standard error of different sub-tests for different age groups are given in Table 5.


The raw and standard scores of children with developmental language disorders in different age groups are given in Table 6.


As indicated in the above Table, the developmental diagnostic criterion is more than 1.25, with a standard number of 6 for different subtests. The results showed that of 13 cases of children with developmental language disorders, 12 had deficits with a lower standard of 6. There was only one child with a deficiency in one subtest.
The analysis of the speech samples based on 2 picture stories of 1200 children are given in Table 7.


The research indicates different indices of quality of speech, fluency, and MLU. The results suggest these figures’ developmental growth for other age groups. The results for each age group are indicated in Table 7.

Discussion
As mentioned, this study aimed to develop a reliable and standardized developmental clinical linguistic battery for Persian-speaking children in different age groups. With respect to the structure of the battery, it was important to include various linguistic subsystems of phonology, morphology, syntax, and semantics of the Persian language. With this aim in mind, the structure of the present developmental battery consists of 9 subtests, 105 items, and 2 illustrative pictures to collect valid data from one thousand and two hundred 3- to 7-year-old Persian-speaking children. The results of the norms obtained for each age group will also allow us to measure developmental language disorders in children with language disorders. The results of each section are given in Tables 1, 2, 3, 4, 5, 6, 7.
For the development of a valid developmental battery, 4 criteria have been considered. The first criterion was to have a valid battery to cover the target group’s major psycholinguistic abilities considering the battery’s formal and content validity. It is also important to consult with the expert panel to check the CVR of the battery. Based on the results, the content validity was 0.78, and Cronbach α was 0.76. The analysis of the collected data indicates that the correlation between different sub-tests proved acceptable, with a variation of 0.832. 
In addition, to check the diagnostic validity, this test was performed on 13 children with developmental language disorder, and the results showed that all of them had delays of about 1.25 standard deviations or more in two or more sub-tests [15]. The assessment findings of children with specific language disorders using language developmental tests are consistent with previous observations and studies [15, 37].
The aim of designing this test is Identifying young children with developmental language disorder, determining the domain of disorder, the degree of delay compared to their normal peers, and  helping for treatment planning as well as to measure the efficacy of rehabilitation. Regarding language levels, this test is more comprehensive than other available tests in Persian [25]. The results of assessing children with developmental language disorder show the vulnerability of all levels of language in these children, which is in agreement with the previous studies reported in Persian (Nilipour et al. [16] and Ahadi et al. [17].
The analysis of collected speech samples based on two picture stories has shown that verbal fluency and MLU have the best developmental trends among different age groups and can be evaluated as the best indicators of speech quality.
Based on the results of assessing children with developmental language disorders, the obvious language deficits include problems in morphology and repetition of non-words and sentences. Of course, it should be noted that significant heterogeneity has been observed among children with developmental language disorders, which has made it difficult to identify the underlying nature of such disorders.Baird [2] have proposed four different subcategories for developmental language disorders, i.e., syntactic, phonological, lexical, and pragmatics. People with syntactic-specific language impairments have difficulty understanding “Wh” questions. In contrast, this task is completed in the case of lexical or pragmatic impairments, so they need different evaluations and treatments. Therefore, we must examine various linguistic abilities to fully diagnose and evaluate developmental language disorders. Thus, in the design of this test, we tried to present a complete picture of the linguistic capabilities of children. 
One of our limitations in this test is the small number of children with developmental language disorders and the lack of background information variables affecting the language performance of such children, such as their family’s economic and social status. Therefore, in future studies, it is suggested that this test is used to measure the relationship between background variables and each child’s performance. It is also recommended that the battery be used in many children with developmental language disorders to provide a clearer clinical picture of children with developmental language disorders. On the other hand, it is suggested that the short version of this battery is used to screen Persian-speaking children in their preschool age.
Finally, the results of the present normative data of this battery are clinically valid as an indication of the level of linguistic development for each age group. Based on the results, the severity of language impairments of each age group can also be determined by comparing the norms of each age group with the results of children with developmental language disorders of the same age. The battery can also be used to measure the efficacy of rehabilitation of 3- to 7-year-old Persian-speaking children by comparing the results before and after any intervention. 

Ethical Considerations
Compliance with ethical guidelines
The study objectives were explained to the parents of children and they were assured of the confidentiality of their information and were free to leave the study at any time.

Funding
This research was supported by the research project, Funded by Cognitive Sciences & Technologies Council (Grant No.: 4013).

Authors' contributions
Data analysis: Hourieh Ahadi and Abbas Pourshahbaz; Editing & review: Reza Nilipour and Hourieh Ahadi; Conceptualization, methodology, and writing: All authors

Conflict of interest
The authors declared no conflict of interest.

Acknowledgments
The authors would like to thank the speech therapists and mothers and children for their cooperation in this study. 


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