Dear Dr. Serra,

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PLOS One

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

Reviewer #4: Partly

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2. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: N/A

Reviewer #3: N/A

Reviewer #4: No

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3. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: No

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Reviewer #1: Title: Mathematical Skills in Deaf Patients: A Systematic Review

Journal: ??

Manuscript ID: PONE-D-26-21292

Summary:

This manuscript is a literature review of studies conducted to examine the mathematics performance of Deaf children under the age of 18 years of age. Using a highly restrictive set of review criteria, the body of mathematics research in the field was reduced to a set of 9 studies. A review of these studies indicates that hearing loss itself is not a cause of low mathematics performance, but rather the low language and educational situations that may accompany the hearing loss.

Strengths:

Mathematics is an under-researched area of study in Deaf Education so research that focuses on this area is much needed. The manuscript is interesting and well written.

Areas of Concern:

• The reference to the Deaf individuals under focus in this manuscript as “patients” in the title is concerning to this reviewer. In every study reviewed in this manuscript, the participants were children. The children were students at a school, or members of a family- they were not sick, and they were not in a hospital. Please find a new word.

• By using such highly restrictive criteria, many good studies were eliminated from review that might have provided good information.

• The authors state in the conclusion that “These limitations highlight the need for more robust and methodologically rigorous research, including clearer descriptions of linguistic and cognitive profiles and standardized assessments targeting distinct mathematical domains.” While this reviewer does not doubt the validity of this statement, it is important to remember the characteristics of the population that one is working with. Deaf children are a very heterogenous population. Cognitive profiles are dependent on language, and these are often difficult to determine when children are young. Then, in using standardized assessments, whom should these assessments be standardized on? Hearing children? Tests standardized for hearing children are often not appropriate for deaf children, and tests created for Deaf children are difficult to develop because of the heterogeneity of the population. The challenges to creating rigorous research are numerous in Deaf Education. Nevertheless, there is at least one study out there, that this reviewer knows of, that did use a standardized assessment- for a population in the appropriate age range that was not included in the literature review for this manuscript. Not sure why.

Reviewer #2: The topic is highly relevant to the fields of mathematics education, special education, and cognitive development. Overall, the study addresses an important gap in synthesizing evidence on domain-specific mathematical abilities and the role of linguistic access in DHH learners.

Major strengths

The review demonstrates several strengths. First, it follows PRISMA 2020 guidelines and uses a predefined protocol registered on OSF, which enhances transparency and reproducibility. Second, the search strategy is comprehensive, covering major databases (PubMed, Scopus, Web of Science) and employing both controlled vocabulary and free-text terms. Third, the inclusion of a structured quality appraisal using JBI tools adds methodological rigor and allows for a nuanced interpretation of study quality. Finally, the narrative synthesis is well-developed and appropriately highlights the heterogeneity of findings, particularly the distinction between linguistic and non-linguistic mathematical tasks.

Major concerns

Despite these strengths, several methodological and reporting issues require attention:

Inconsistencies in study selection reporting

There is inconsistency in the number of included studies. The manuscript reports both eight and nine included studies in different sections. Additionally, the PRISMA flow reporting contains numerical inconsistencies (e.g., 579 records minus exclusions does not consistently lead to the reported final sample). These discrepancies should be carefully verified and corrected.

Clarification of eligibility criteria

The inclusion/exclusion criteria are detailed but somewhat repetitive and occasionally unclear (e.g., overlapping descriptions of study designs). A more concise and structured presentation of PICOS criteria would improve clarity.

Lack of quantitative synthesis justification

Although a meta-analysis is not required, the authors should more explicitly justify the absence of quantitative synthesis. Given that some included studies report comparable outcomes, a brief discussion of effect size heterogeneity or feasibility of meta-analysis would strengthen methodological transparency.

Quality appraisal interpretation

While JBI tools are appropriately applied, the categorization of risk of bias (low/moderate/high) appears partially subjective and not fully standardized. A clearer explanation of thresholds and consistency across different JBI checklists is needed. Additionally, combining qualitative and quantitative studies under similar appraisal logic may require further justification.

Heterogeneity of included studies

The included studies vary substantially in design, sample size, age range, and outcome measures. Although this is acknowledged in the discussion, a more structured subgroup interpretation (e.g., by age group, task type, or communication modality) would improve analytical depth.

Older studies and methodological limitations

Several included studies are dated (e.g., 1975), and their methodological limitations are acknowledged. However, their influence on overall conclusions should be more critically weighted, as older methodologies may not be fully comparable to contemporary research standards.

Language and reporting clarity

Minor grammatical inconsistencies and repetition appear throughout the manuscript (e.g., repeated phrases in Methods and Results sections). A careful language revision is recommended to improve readability and precision.

Minor comments

The PRISMA flow description should be aligned with the final included study count.

Table formatting (especially Table 2) would benefit from standardization for readability.

Some methodological terms (e.g., “moderate–high quality”) require clearer operational definitions.

Keywords could be refined to better align with indexing databases.

Ethical and publication considerations

No major ethical concerns are identified, as the study is based on published literature. However, the authors should ensure full transparency regarding protocol adherence and clarify whether any deviations from the registered protocol occurred. Additionally, consistency in reporting is essential to avoid concerns regarding data handling or selective inclusion.

Conclusion

This systematic review addresses an important and underexplored area with clear relevance to education and developmental psychology. With revisions to improve consistency, methodological transparency, and reporting clarity, the manuscript has the potential to make a meaningful contribution to the field.

Reviewer #3: Introduction

The manuscript entitled “Mathematical Skills in Deaf Patients: A Systematic Review” offers a valuable and timely contribution to the growing body of literature examining cognitive and educational outcomes among deaf individuals. By synthesizing existing research on mathematical performance within this population, the authors provide important insights into both the challenges and potential strengths associated with numerical cognition in deaf learners. The review is particularly commendable for its thorough methodology and its well-developed discussion section, which thoughtfully interprets findings and situates them within broader educational and cognitive frameworks.

Overall, the authors have demonstrated considerable effort in compiling and analyzing relevant studies, and their work has clear implications for both research and practice. However, despite these strengths, there remain several issues that should be addressed to further improve the clarity, rigor, and impact of the manuscript. These concerns are outlined below.

Title & Abstract

• The title is precise and reflect the content, nevertheless, using the term “Deaf Patients” does not match the focus. The review is about children in education. It would fit better to say “Deaf and hard-of-hearing children and adolescents” or “DHH learners.”

• The abstract is clear, but it is missing key details; Mainly, how many databases you searched, the time period for the study, and the reason for the use of narrative synthesis instead of a meta-analysis.

• According to the criteria, the paper included only nine studies, and their quality varies. I think the researchers should be careful in presenting the results where it sounded stronger than they are.

Introduction

• The reason for the study is clear. The link between math skills and daily life is easy to understand.

• The section on developmental dyscalculia gets quite a lot of space relative to its role in the review. Further explanation is needed clearly why it's included as a comparator — and why wasn’t this issue featured in the discussion.

• The introduction would benefit from a sharper statement of what gap in the existing systematic evidence this review is actually filling. It's implied, but never said directly.

Methods

• The protocol statement needs fixing. The link is broken and the format is unclear. Include the platform, number, date, and whether it was registered before screening. Remove the extra “ù” symbol before the Inclusion Criteria and Eligibility.

• The research question — "What is the impact of deafness on the development of mathematical skills?" — is too broad and implies CAUSALITY that observational studies can't establish. Since your criteria limit the population to under 18 years, the question should ask about the association between DHH and mathematical skill development among DHH children and adolescents?" this might be more appropriate and safer about the study designs involved.

• The eligibility criteria need a few clarifications:

o Were both congenital and acquired hearing loss included?

o Was the severity of hearing loss a factor?

o The phrase "when applicable" for the comparator group is vague — were studies without a comparison group eligible or not?

o The outcome criterion is broad; the researchers needed to be specific about which cognitive processes counted and how they relate to mathematical outcomes.

• The search strategy is well reported. But using terms like “cohort” or “cross-sectional” may have excluded studies. Either explain this choice or remove those filters Adding ERIC, PsycINFO, EBSCO, or Education Source would also strengthen the coverage for this field.

• The study selection process is described well, but the data extraction process is barely mentioned. Readers need to know who extracted the data, whether it was done independently or checked by a second person, what form was used, and how disagreements were resolved. If inter-rater reliability was calculated, report it.

• The quality appraisal is mostly appropriate, nevertheless, it was mentioned that cross-sectional checklist has nine items but list eight, this inconsistency needs to be fixed. The phrase "moderate expertise" for the reviewers slightly undermines confidence in the process, use more appropriate words focusing mainly on the training rather than the level. Furthermore, Also clarify how disagreements were resolved before involving the third reviewer.

• Your quality scoring is not standard for JBI. Either justify it or say you created it. It is better to say “higher,” “moderate,” or “lower quality.”

• One qualitative study was included, but this is not in the criteria. If qualitative studies were allowed, say so. If not, explain why it was included.

Results — Screening & Flow Diagram

• The numbers are inconsistent. You say eight studies in one place and nine in another. Use one number everywhere.

• The PRISMA diagram is useful. But do not mix duplicate removal with other exclusions. Also, “not retrieved” is confusing.

• "Does not match with our topic" as the reason for excluding 500 records is too vague. Even a brief list of the main reasons at that stage — wrong population, wrong outcome, wrong design — would make the screening process more transparent and reproducible.

Table 2 — Study Descriptions

• Several studies are listed without exact sample sizes. Try to include numbers for all. If estimated please mention it. Leaving it blank makes it very hard to assess the weight of evidence.

• A few details are missing, like country and journal names. Study 22 (Laria et al.) is missing a country and journal name. Study 21 (Ross & Hoemann, 1975) is missing the journal

• The results column is not consistent. Some are short, others are long. Make them all similar.

• Kritzer (2009) is qualitative, but this was not listed in the methods. Fix this mismatch.

Table 3 — Methodological Quality

• Different checklists were used, but the same percentage rules were applied. This is not fully fair. Either adjust the percentages or describe quality in words (8-item JBI cross-sectional checklist vs 11-item case-control checklist vs Kritzer with the 10-item qualitative checklist)

• One study -(Ross & Hoemann (1975)- was labeled experimental but assessed as cross-sectional. Explain this choice or fix it.

Discussion

• The authors did a good job in the discussion being the strongest part. The argument is clear and balanced.

• Check the citation numbers carefully. Some do not match across sections.

• The main finding is repeated too many times. Say it clearly once, then support it.

• Dyscalculia is discussed early but not here. Either connect it or reduce it in the introduction.

Conclusion & Limitations

• The conclusion is balanced and realistic. It ends with a useful message.

• Add two missing limitations. First, no grey literature or education databases. Second, the search filters may have been too strict.

• The final sentence is too strong. “Comprehensive” is not accurate for nine mixed studies. Use a more modest ending.

Reviewer #4: To ensure a comprehensive and rigorous evaluation of the manuscript, the complete peer-review comments, including specific technical assessments and detailed editorial recommendations, have been systematically compiled and uploaded as a separate attached document. Please consult the attached file for the full report.

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what does this mean?). If published, this will include your full peer review and any attached files.

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: Yes:  Hatem Alkhamra

Reviewer #4: Yes:  Wenda Alifulloh

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Attachment

Submitted filename: Peer Review Report.docx

Attachment

Submitted filename: Comment - Systematic review -math skills-deaf_Final_ver3.docx

Mathematical Skills in Deaf and Hard-of-Hearing Children: A Systematic Review

PONE-D-26-21292R1

Dear Dr. Serra,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Rana Alkhamra

Academic Editor

PLOS One

Additional Editor Comments (optional):

Thank you for submitting the revised version of your manuscript and for providing a comprehensive and thoughtful response to the reviewers’ comments.

Following evaluation of the revised manuscript and your point-by-point responses, I am pleased to confirm that the concerns raised during peer review have been satisfactorily addressed. The revision demonstrates careful consideration of the reviewers’ recommendations and has resulted in substantial improvements in the methodological transparency, internal consistency, clarity, and overall presentation of the work.

Accordingly, I consider the manuscript suitable for publication and am pleased to accept it for publication in the journal.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #3: All comments have been addressed

Reviewer #4: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions??>

Reviewer #3: Yes

Reviewer #4: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #3: Yes

Reviewer #4: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #3: Yes

Reviewer #4: Yes

**********

Reviewer #3: (No Response)

Reviewer #4: (No Response)

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what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review?  For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #3: No

Reviewer #4: Yes:  Alifulloh, Wenda

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