Introduction
Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by substantial deficits in communication skills and restricted/repetitive behavior patterns [1]. Early communicative skills emerge during the prelinguistic stage, typically at 9 months of age, when intentional communication begins. These skills encompass behaviors such as gesture use, eye contact, vocalizations, and single-word expression, serving functions like behavior regulation (requesting and rejecting), social interaction, and joint attention [2]. Additionally, key cognitive skills in the prelinguistic stage, such as play, imitation, and object permanence, develop during the initial stage of intentional communication (approximately 9–12 months). Research indicates that these skills are crucial for later language development in both typically developing (TD) children and those with developmental disorders [3, 4]. Children with ASD exhibit significant impairments in communicative skills, including limited or absent use of gestures, eye contact, varied vocalizations, and joint attention compared to TD peers [5–8]. Beyond communication, cognitive abilities are also affected; children with ASD often show deficits in various types of play, particularly pretend and symbolic play, and in imitation [9]. Studies suggest that impairments in early communication and cognitive skills during early childhood increase the risk of ASD development [7, 10]. Given the critical role and vulnerability of these skills in children with ASD, their assessment is essential for early identification of at-risk children and for establishing communication profiles to guide therapeutic interventions [11]. Theoretical frameworks, such as social interaction theory, and intervention models such as the social-pragmatic developmental approach and prelinguistic milieu teaching (PMT), emphasize the importance of assessing these skills in children with ASD, focusing on early detection and individualized treatment [12, 13].
Various methods, including parent–child interaction observations and parent-report checklists, have been used to study early communication in children with ASD and identify at-risk children. Parent-report tools have demonstrated high validity and reliability [14, 15]. Internationally, prominent parent-report tools include the communication and symbolic behavior scales – infant toddler checklist (CSBS-ITC) [16] and the MacArthur–Bates communicative development inventories–1 (CDI-1) [17]. However, the CSBS-ITC does not assess skills such as imitation, nonverbal comprehension, or phrase production, while the CDI-1 primarily focuses on receptive and expressive vocabulary [18, 19]. Numerous studies have examined early communication skills, such as joint attention, imitation, and vocalizations, and their predictive role in later language development using various tools [20–24]. For instance, Hamrick et al. used the autism diagnostic observation schedule–2 (ADOS-2) to evaluate nonverbal communication in children with ASD aged 18–70 months, aiming to improve screening accuracy and reduce diagnostic errors [20]. Maes et al. employed the CDI-1 to assess vocal output (vocalizations and early words) in children with ASD aged 3–5 years, without comparing them to TD peers [25]. Vennes c et al. conducted a longitudinal study using the CSBS DP-ITC and CDI-1 to identify early ASD markers in children aged 12–24 months later diagnosed at age four, comparing them to TD children, those with language impairment, and those with developmental delays; however, no within-group ASD comparisons or examinations of older age groups were performed [26].
In Iran, research on early communication skills has primarily focused on specific abilities, such as nonverbal communication or early vocabulary, in TD children, often to validate screening tools [27–31]. For example, Oryadi-Zanjani developed the children’s nonverbal communication scale (CNCS) for TD children aged 3–18 months but did not apply it to children with ASD [27]. Kazemi et al. examined the psychometric properties of the CDI-1 in TD children aged 8–16 months [32]. This tool has also been used to assess receptive and expressive vocabulary in Persian-speaking children with ASD, for example, in Teimouri et al.’s study on remote interventions [33]. Most Iranian studies on minimally verbal or nonverbal children with ASD emphasized intervention effects on early communicative skills or examined selected abilities [34, 35]. Dadgar et al. used the early social communication scales (ESCSs) to evaluate nonverbal communication in children with ASD aged 3–5 years and assess its relationship with imitation and motor skills [35]. Abdi et al. assessed pivotal response treatment effects in Iranian children with ASD aged 2–6 years using the Persian version of the autism treatment evaluation checklist, a diagnostic tool covering speech, language, communication, socialization, sensory awareness, cognition, and health [36]. 
A review of Iranian studies reveals that no studies have systematically investigated early communication skills using specialized instruments to compare them between ASD children and their TD peers. One available tool is the communication skills checklist (CSC), developed by Bayat et al. to screen early communication and related cognitive skills in Persian-speaking TD children aged 6–24 months. The CSC has strong psychometric properties and is completed by primary caregivers, typically mothers [37]. This study used the CSC to: (a) assess early communication skills in Persian-speaking minimally verbal or nonverbal children with ASD at the initial intentional communication stage aged 3–5 years, since formal ASD diagnoses in Iran typically occur after age three [38, 39], and expressive language often emerges during this period [25]; (b) compare these skills between age groups in both ASD and TD children; and (c) compare skills between ASD and TD children aged 9–12 months matched for communicative developmental level [40-43].

Materials and Methods
Study design and participants
This is a descriptive–analytical study with a cross-sectional design conducted in Tehran, Iran, during 2023–2024. Participants were 70 children with ASD aged 3-5 years and 132 TD children aged 9–12 months. The ASD group was subdivided into three age groups (3, 4, and 5 years), with at least 23 children per group. The TD group was divided into four age groups (9, 10, 11, and 12 months), with at least 25 children per group. The two groups were matched for the communicative developmental level. Inclusion criteria for both groups were being monolingual Persian speakers, residing in Tehran, and having mothers proficient in Persian speaking and writing. For the ASD group, additional inclusion criteria were chronological age 3–5 years; ASD diagnosis by a child psychiatrist based on the DSM-5 criteria, documented in medical records; absence of severe comorbid sensory, motor, metabolic, or genetic syndromes; having at least early intentional communication; and, for verbal children, a spontaneous vocabulary of at most 3–5 words using the CDI-1. For the TD group, additional inclusion criteria were chronological age 9–12 months, no parental developmental concerns, absence of genetic syndromes, physical impairments, or hearing loss, and no preterm birth history, based on medical records or using a researcher-designed checklist. The exclusion criterion for both groups was the incomplete return of questionnaires.
Children with ASD were recruited using a convenience sampling method from rehabilitation centers in Tehran. Eligibility was assessed using clinical records and CDI-1 results. If the criteria were met, informed consent was obtained from their mothers. For the TD group, recruitment was conducted using two approaches: In-person and online sampling (due to the onset of the respiratory disease season during data collection). In the in-person sampling method, health and vaccination centers affiliated with Tehran University of Medical Sciences, Iran University of Medical Sciences, and Shahid Beheshti University of Medical Sciences were first randomly selected. The research team then attended these centers, selected eligible boys and girls using a convenience sampling method. In the online sampling method, recruitment was also conducted using a convenience method following the distribution of an invitation poster on social media platforms such as Instagram. The poster provided information about the study objectives. Interested mothers contacted the research team, and the inclusion criteria were assessed through an online interview with the principal investigator.

Instruments
Data collection in the present study was conducted using three instruments: A demographic form, the CSC, and the CDI-1.
The CSC is a validated tool in Persian for screening communication skills in TD children aged 6–24 months, which is completed by parents or primary caregivers (mothers). It includes 36 items (33 on a three-point Likert scale, and 3 on a five-point scale) assessing prelinguistic domains: Communication (16 items, max score 32; gestures, eye contact, facial expressions, functions), expression (4 items, max score 12; word production, vocalizations, phrases), comprehension (7 items, max score 14; verbal/nonverbal), and play/imitation (9 items, max score 20; play types, imitation, object permanence). The total score ranges from 0 to 78. It has a Cronbach’s α of 0.95 and a test re-test reliability of 0.93 [37].
The CDI-1 is a parent-report tool assessing receptive/expressive vocabulary and gesture use in TD children aged 8–16 months, also applicable to older children with developmental disorders like ASD. The Persian version, validated by Kazemi et al., has a Cronbach’s α of 0.43–0.98 across subscales [32].

Data analysis
For performing data analysis, SPSS software, version 25 was used. Descriptive statistics were used to describe demographic factors (age, gender, parents’ education/occupation). Mean±SD were used to describe the CSC domain scores. Data normality was confirmed. One-way ANOVA followed by Tukey’s post-hoc was used to compare the scores within ASD and TD groups. Independent t-test was used to compare the scores between the groups.

Results 
Characteristics of participants
Table 1 presents the demographic characteristics of the participants in the two groups.


It should be noted that some mothers of children with ASD, after participation in the study, were not willing to provide information about their own or their husbands’ employment and educational level for personal reasons.

Early communication skills in children with ASD and TD children
Mean±SD of CSC scores for domains (communication, expression, comprehension, play/imitation) and total are in Tables 2 and 3.





Figure 1 illustrates the comparison of mean scores for two groups of children of different ages.
Within-group comparison of children 
The within-group comparison of the CSC scores (domain and total) among the three age groups of children with ASD (3, 4, and 5 years) indicated that 5-year-old children had higher scores, but the differences were not significant (P>0.05). For TD children (9–12 months), one-way ANOVA results indicated significant differences among the four age groups (P<0.05). Tukey’s post-hoc test results revealed that 12-month-old TD children scored significantly higher than 9-month and 10-month-old children in all CSC domains and total CSC score (P<0.001). Differences between 11 and 12-month-old TD children were significant in all domains (P<0.001) except for the play/imitation domain. Nine-month-old TD children differed significantly from 11-month-olds in scores of the communication and play/imitation domains and total score, but not from 10-month-old children (P>0.05). No significant differences existed between 10- and 11-month-old TD children (P>0.05).

Between-group comparison of children 
The t-test results showed no significant differences in total or domain scores of the CSC between children with ASD (3–5 years) and TD children (9–11 months) (P>0.05), indicating their similar early communication performance. The expression domain scores were slightly higher in children with ASD due to rehabilitation interventions and minimal verbal output, but lower than in 12-month-old TD children. The communication domain scores were significantly lower in children with ASD than in 9–11-month-old TD children (P<0.05). All CSC domains and the total CSC score in ASD were significantly lower than in 12-month-old TD children (P<0.001).

Discussion 
In the present study, early communication skills (CSC domains including communication, expression, comprehension, play/imitation) were investigated in 70 Persian-speaking children with ASD aged 3 to 5 years, who had minimal or no verbal output and were in the prelinguistic stage of communicative development. These skills were then compared with those of 132 TD peers aged 9-12 months. The findings indicated that children with ASD scored significantly lower than 12-month-old TD children in all CSC domains.
Comparisons of early communication skills among 3-year, 4-year, and 5-year-old children with ASD revealed no significant differences among age groups. This similarity may be attributed to the age at diagnosis, intervention variability, and ASD heterogeneity. This is consistent with the results of Maes et al., Hamrick et al., and Venker et al. [25, 20, 44]. Other studies have also shown that delays or differences in the development of communication skills in children with ASD can make it difficult to compare them with each other [45].
Among TD children aged 9-12 months, significant differences in early communicative skills were observed, where older children had higher CSC scores, consistent with the results of Bayat et al., Babaei et al., Şimşek et al., and Delehanty and Wetherby, who demonstrated that in children under 24 months, early communication skills develop with the increase of age [30, 31, 46, 47].
Differences between children with ASD and 9–11-month-old TD children were not significant in overall, though TD children scored higher in comprehension, aligning with the results of Trevisan et al. and Dimitrova and Özçalışkan [48, 49]. This finding is probably due to the similarity of the communication performance of children with ASD and TD children aged 9 to 11 months, due to delays in the development of communication skills in children with ASD [19, 26]. 
The communication scores (eye contact, gesture use, communicative functions) were lower in children with ASD than in any age groups of TD children, reflecting core deficits in communication, consistent with the results of Veness et al., MC Dennis, Manwaring et al., and Wu et al., and Dennis [26, 50–52]. Some studies that examined early communication skills in children with ASD using tools other than the CSC have also reported significant differences and lower communication scores in children with ASD compared to TD children [53]. Other studies have also shown delayed or deviant patterns in expressive gestures, eye contact, and significant impairment in communicative functioning, especially joint attention [54].
Twelve-month-old TD children significantly outperformed children with ASD in all early communication skills, likely due to rapid skill acquisition at age 12 months, widening the developmental gap between the two groups. Studies in this field have shown that in 12-month-old TD children, the number of initial vocabulary words and the variety and form of phonemes have increased and they can have about five expressive words and can often produce linguistic consonants in various syllables, starting to use expressive movements, and their games progress towards early symbolic games [55].
There were some limitations in this study. The ASD group sample size was smaller than the TD group, and the familiarity of ASD children’s parents with communication skills (due to prior rehabilitation experiences) may have influenced responses. Future research should apply the CSC to younger children with ASD cohorts and use larger sample sizes and other groups with developmental language delays.

Conclusion
This is the first study to assess early communication skills in Persian-speaking children with ASD using the CSC tool, and to compare them with TD children matched for developmental—but not chronological—level. Findings reveal that 3–5-year-old children with ASD, despite their older age, display substantial delays in early communication, sometimes performing comparably to much younger TD peers. The results highlight the necessity of early screening and detection of communication delays or deviations in ASD children, and demonstrate the CSC tool’s potential as a brief, parent-report tool for clinical and research use.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of the University of Social Welfare and Rehabilitation Sciences, Tehran, Iran (Code: IR.USWR.REC.1402.102). Written informed consent was obtained from all parents prior to data collection, and all participant information was coded to ensure anonymity.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for profit sectors.

Authors' contributions
Conceptualization and data analysis: Fateme Ghovati, Atieh Ashtari, Farin Soleimani, Talieh Zarifian, and Mohsen Vahedi; Investigation: Fateme Ghovati, Atieh Ashtari, Farin Soleimani, and Talieh Zarifian; Methodology: All authors; Review and editing: Fateme Ghovati and Atieh Ashtari; Supervision: Atieh Ashtari and Farin Soleimani; Validation: Atieh Ashtari, Farin Soleimani, and Talieh Zarifian.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgments
The authors would like to thank the staff of the health and vaccination centers of Tehran, Iran, and Shahid Beheshti Universities of Medical Sciences and the mothers of children with ASD and TD participating in this study who helped them in this research.



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