Introduction
It is possible to develop proficient listening and speaking skills when one possesses a healthy hearing system. However, sensory-nerve damage in the auditory system during childhood, which is the period of learning language and communication skills, inflicts serious damage to language acquisition, speech development, listening skills, and children’s communication. Hard of hearing can create many problems in the child’s development process, including academic, emotional-psychological, social, and occupational [1]. Nonetheless, these problems can be prevented by timely interventions and hearing rehabilitation, with a particular emphasis on auditory and language rehabilitation [2]. Acquiring listening and language skills hinges on certain times, called sensitive periods of speech, language, and listening skills development; it usually spans from birth to 3 years old, with continued learning occurring until five [4]. A rehabilitation program helps children obtain the maximum auditory information necessary for language and social skills development during the sensitive language learning period. The first years of a child’s life comprise the main period of learning language and speech [1]. During this period, the child spends much time with family members, making parents the primary educators for deaf children [3]. 
Preverbal skills may serve as a natural predictor of language development in children [8]. The preverbal communication system, a prerequisite for developing spoken language, possesses a social nature, and its purpose is to communicate with others. It emerges through interactions between a child and an adult in the first years of a child’s life. Some preverbal skills include eye contact, joint attention, taking turns, pointing, and imitation [2]. Preverbal skills in children whose hearing loss was diagnosed at a young age and benefit from appropriate intervention and rehabilitation services grow faster than children who did not receive appropriate intervention services at a young age [2]. Since 1970, family-oriented early intervention programs have been recognized as vital and effective strategies for rehabilitating deaf and hard-of-hearing children [13]. Reading storybooks is a crucial opportunity for language learning [7]. It greatly contributes to language and speech development and provides a basic learning opportunity related to reading ability. Interactions between parents and children during book reading in various contexts, especially when engaging in dialogues, are crucial for fostering children’s literary literacy [15]. Dialogic parent-child book reading strengthens children’s listening and language skills and understanding of unfamiliar words [9]. Also, dialogic parent-child book reading shows positive results regarding the development of literary literacy of deaf children and deaf people in general [8]. Therefore, paying attention to environmental stimulation and timely interventions for organizing primary sensory modalities in the development of hard-of-hearing children and their literary literacy is essential. 
Given the family’s prominent role in the educational and therapeutic development of children with special needs, especially deaf and hard-of-hearing children, this study was conducted to design an online dialogic parent-child reading program. This program aimed to reinforce preverbal and auditory stimuli based on the needs of hard-of-hearing and deaf children and their parents.

Materials and Methods 
This research is a quasi-experimental study employing a one-group pre-test-post-test design. The statistical population included all Persian-speaking deaf children under 3 years old who have hearing parents and were members of the Iranian Deaf Family Association and the Iranian Deaf Center. Based on the interviews conducted, the statistical population of the present study was very limited, primarily due to the outbreak of COVID-19 and the application of the inclusion criteria. To address this challenge, the research team identified everyone meeting the inclusion criteria. Then, the researchers explained the study's objectives and obtained informed consent from potential candidates (Appendix 1). In the end, 13 parents and their children who met the inclusion criteria and accepted to participate in this research were considered for the intervention. In this research, the samples were first identified by purposive sampling (who met the inclusion criteria). Then, among the eligible families, parents who expressed their readiness to participate in the study alongside their children were selected as study samples. These children were in the age range of under one to three years old. 
In continuation, three samples were excluded from the study due to missing the intervention sessions for two consecutive weeks. The intervention program was subsequently completed with 10 parents. The questionnaires were provided online to the parents before and after the intervention program (pre-test and post-test). A dialogue-based book reading workshop was conducted for mothers of hard-of-hearing children in groups of 3 to 4. Also, the mothers of deaf children joined a WhatsApp group named “parent-child storybook reading group” to exchange information and provide content. Book reading sessions were conducted online for 20 sessions three days a week, at a specific time (10:00 AM on even days) for 20 minutes. 
Every day, a book with pictures and contents related to the story, along with explanations and questions related to the book and additional activities, was posted in the WhatsApp group. The parents raised questions if they had any and shared pictures, videos, or audio recordings of the book reading, along with additional activities of the previous session in the group. Between the sessions, parents had time to read to their children and give their feedback to the researcher in the next session. Furthermore, parents were required to record audio or video of their weekly reading with children and submit them as a work report. The post-test was conducted using the preverbal skill questionnaire to evaluate the preverbal skills of hard-of-hearing children. Additionally, the LittlEARS auditory questionnaire (LEAQ) in the form of video and voice calls was conducted on WhatsApp under the supervision of speech therapy experts. After completing all these steps, the study data were collected and analyzed in two parts: Descriptive and inferential statistics. The tests used included the Kolmogorov-Smirnov test and the paired t-test.

Results
As shown in Table 1, the Kolmogorov-Smirnov test yielded non-significant results for all variables in the studied group.


The non-significance of this test implies that the data have a normal distribution. Therefore, due to the normality of the data distribution, the paired t-test was used to analyze the research hypotheses and compare the mean differences within the two dependent groups. 
According to Table 2, the pre-test mean value of the preverbal skills of the subjects was 4.26, and the post-test mean of this variable was 5.66.


Therefore, the mean preverbal skills of the children increased in the post-test. 
The paired t-test was used to compare the pre-test and post-test scores of deaf children’s preverbal skills. As the significance level of the paired t-test (P=0.001) was <0.05 (Table 3), online dialogic parent-child book reading increased the preverbal skills of deaf children. 


According to Table 4, the pre-test mean value of the subjects’ pointing skill was 7.200, and the post-test mean of this variable was 8.900.


Therefore, the post-test mean value of the pointing skill of the children increased. 
According to Table 5, the mean pre-test value of the turn-taking skill of the subjects was 2.100, and the mean post-test of this variable was 3.600.


Therefore, the mean posttest value of the turn-taking skill of the subjects increased.
According to Table 6, the mean pre-test value of the imitation skill of the subjects was 3.500, and the mean post-test of this variable was 4.500.


Therefore, the mean post-test of the imitation skill of the subjects increased.
According to Table 7, the mean pre-test value of the joint attention skill of the subjects was 4.400, and the mean post-test value of this variable was 5.700.


Therefore, the mean post-test value of the joint attention skill of the subjects increased.
According to Table 8, the mean pre-test value of the listening skill of the subjects was 11.50, and the mean post-test value of this variable was 15.


Therefore, the mean post-test of the listening skill of the subjects significantly increased.
According to Table 9, the significance level of paired t-test (P=0.001) is <0.05.


Therefore, online dialogic parent-child book reading increases the listening skills of deaf children.

Discussion
This research was conducted to investigate the effectiveness of online dialogic parent-child book reading on the listening and preverbal skills of deaf children under the age of three. The results showed a significant difference between the pre-test and post-test scores in parent-child book reading for deaf children. In simpler terms, the dialogic parent-child book reading program significantly increased the listening and preverbal skills of deaf children under three years old. When deaf children do not receive early and appropriate interventions during their critical verbal and hearing developmental period, they are more likely to exhibit communication and verbal problems than their hearing peers. One of the methods that can help deaf children to improve these skills is dialogic book reading. 
It is assumed that deaf children in their sensitive developmental ages primarily interact with their parents, their first and closest companions. Therefore, if parents learn and apply suitable intervention methods for their children, they will be much more effective in their child’s developmental process. Although we could not find similar studies to the present research, some studies investigated the effectiveness of early interventions, including book reading and storytelling programs, on children in preschool and school ages. Among them, we can mention the studies conducted by Greenhut and Beyer [6], Rezaiyan et al. [20], and Kaderavek et al. [7].
Using pictures during book reading increases interactions and also serves as a practical means to improve the basic literacy skills of both parents and children [7]. Before book reading, hard-of-hearing children should have an opportunity to discover and interact with the book and the parents. This interaction helps to establish an effective relationship with the story. Communication and interaction between the child and the parent during book reading increase the children’s literary literacy and verbal skills, consistent with the present research’s goals [13]. In their study, Rezaiyan et al. demonstrated that hard-of-hearing children’s vocabulary, picture comprehension, and oral vocabulary skills improved significantly after participating in online dialogic storytelling sessions. This research reaffirms the effectiveness of dialogue-based methods, including mother-child dialogic storytelling of hard-of-hearing children [20]. 
In elucidating the results of this research, the significant application of dialogic parent-child book reading should be underscored. This approach is highly beneficial due to its effective language facilitation techniques in book reading and the close interaction it fosters between parents and children, thereby establishing communication and enhancing the skills of young deaf children. Several studies support the tremendous impact of storytelling, dialogic book reading, and two-way communication between parent and deaf child on language skills, basic literacy, vocabulary, comprehension of grammar, and heightened translinguistic awareness of the deaf child [21]. Badrul Hisam [22] showed that book reading improved the speech of students with special needs through the pronunciation of expressive words. The basic principle in dialogic book reading is to improve the child’s language skills and transform the child into an active reader and interactive person instead of a passive listener [23]. 
Family-oriented dialogic book reading improves children’s language skills more than conventional reading, a finding supported by numerous studies. Dialogic book reading is a shared reading technique that includes strategic questions and dialogues during the reading process. This approach can increase oral language development and improve children’s basic literary literacy skills [24]. Dialogic book reading helps language acquisition and development. Language development is the process through which a child learns expressive and receptive language. Language acquisition is a process through which children communicate and express feelings and opinions through language [25]. Research shows that spoken language phonology is one of the literacy skills that students should learn to read. Understanding the meaning of words and ideas through book reading helps the child learn language and develop listening comprehension, which is critical to developing basic literary literacy. Babies and toddlers under three should be immersed in literature, especially books featuring rhyme, rhythm, and repetitiveness, to create a solid foundation in language formation.

Conclusion 
The study results highlighted that the book reading based on parent-child dialogue can help parents to rehabilitate their children. This approach can easily be implemented at home. Book reading techniques based on parent-child dialogue can be directly or indirectly taught and implemented in any environment where children and parents convene, such as schools, rehabilitation centers, and social networks. Reading books based on parent-child dialogue is more effective when interventions for hard-of-hearing children are implemented early and consistently. Therefore, incorporating dialogue-based book reading methods within the rehabilitation education of deaf children in early intervention centers and schools can be very effective and useful in the rehabilitation process of these children. 

Study limitations
This research had several limitations. One of the important limitations of the research was the simultaneous implementation of the study with the outbreak of COVID-19. Due to the shutdown of centers and associations, access to a large sample size was difficult. Another limitation was the follow-up period, which could not be realized due to parents’ lack of cooperation. 

Study suggestions 
Based on the study findings, we suggest that dialogic parent-child book reading be conducted with sign language for deaf children. Also, future studies should be conducted in Iran in the field of early and online interventions not only for deaf children but also for other children with various disorders. It is suggested to do a parent-child dialogic book reading with sign language for deaf children with a deaf parent, as well as conduct a study with stronger evidence, such as a randomized control trial.

Ethical Considerations
Compliance with ethical guidelines
This research was approved by the  University of Social Welfare and Rehabilitation Sciences (Code: IR.USWR.REC.1399.076) and informed consent was also obtained from the participants.

Funding
This article was extracted from the Master’s thesis of Sima Razmi, funded by the Department of Rehabilitation Management, University of Social Welfare and Rehabilitation Sciences (Grant No.: 971273005).

Authors' contributions
Writing: Sima Razmi; Supervision: Guita Movallali; Preparing intervention content, editing $ review: Talieh Zarifian; Data analysis: Sina Ahmadi; Final approval: all authors. 

Conflict of interest
The authors declared no conflict of interest.

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


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Appendix 1. Consent to participate in the thesis 
The effect of online dialogic parent-child book reading on preverbal skills and skills of deaf children under three years old. 
1. I was informed that the objectives of this research are as follows: 
• General objectives 
• Determining the effectiveness of online dialogic parent-child book reading on the preverbal skills of deaf children under 3 years old, 
• Determining the effectiveness of online dialogic parent-child book reading on the listening skills of deaf children under 3 years old, 
• Specific objectives
• Determining the effectiveness of online dialogic parent-child book reading on pointing skills of deaf children under 3 years old,
• Determining the effectiveness of online dialogic parent-child book reading on turn-taking skill of deaf children under 3 years old. 
• Determining the effectiveness of online dialogic parent-child book reading on the imitation skill of deaf children under 3 years old. 
• Determining the effectiveness of online dialogic parent-child book reading on joint attention skills of deaf children under 3 years old. 
• Practical objectives 
• Acquaintance of experts of rehabilitation centers and teachers of deaf and hard of hearing children with dialogic parent-child book reading method. 
• Acquaintance of parents of deaf children with the method of dialogic parent-child book reading and using this method at home. 
• Dialogic parent-child book reading can be used in educational and rehabilitation programs for deaf and hard-of-hearing children.
2. I was informed that my participation in this research is entirely voluntary, and I am under no obligation to participate. I was informed that if I do not agree to participate in the research, I will not be deprived of routine diagnostic and therapeutic care. 
3. I was informed that even after initially agreeing to participate in the research, I could withdraw from the study whenever I wanted. My withdrawal from the research will neither deprive me of the usual care, diagnosis, and treatment services nor entail any financial penalties or liabilities. 
4. My cooperation in this research entails the following activities: 
a. Performing book reading for children at home 
b. Being available at specified times to communicate online with the research team 
5. Potential benefits of my participation in this study are as follows: 
a. Increasing the child’s preverbal skills 
b. Increasing the child’s listening skills 
6. Participating in this research may result in some risks and complications: 
• I was informed that in case of severe side effects arising from my participation in the research, the drug and the research method will be discontinued, and the researcher will be responsible for compensating the damages and its cost. 
• I was informed that the planners of this research would keep all the information related to me confidential. They are only allowed to publish this research’s general and group results without mentioning my name and details. 
• I was informed that I will not be responsible for any of the costs of research interventions as follows:
a. Research interventions include evaluating the child’s preverbal and listening skills
b. Holding a training session for parents. 
• I was informed that if any alterations are made to the research process that could affect my health and my decision to continue participating in the project, I will be informed. 
• I was informed that my participation in the study may be terminated in some circumstances, such as absence for more than two weeks in the program. 
• I was informed that the researchers will notify me of the results of this project after completing the research.
• I was informed that the Ethics Committee in Research, located at this address: Evin, Daneshju Blvd., Koodakyar Alley, Rehabilitation Sciences and Social Health University, can access my information to monitor the observance of my rights.
• I was informed that should I have any problems or objections regarding the organizers or the research process, I can contact the Research Ethics Committee at the address: Evin, Daneshju Blvd., Koodakyar Alley, Rehabilitation Sciences and Social Health University and raise my problem.  
Mrs. Sima Razmi was introduced to me as the project director to respond. I was told that if any problem, question, or unwanted complications occurred while participating in the mentioned research, I should share with her and ask for guidance.
Therefore, I……….., the child of……….., bearing the birth certificate number …………and the national code………….., according to the above and obtaining sufficient knowledge, hereby declare my informed and voluntary consent to participate in the above research project. 
Address and contact number: 
Participant’s signature and fingerprint: 
Date: