PONE-D-21-23301Reaching articular limits can negatively impact embodiment in virtual reality.PLOS ONE

Dear Dr. Porssut,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Jan 30 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Imre Cikajlo, Ph.D.

Academic Editor

PLOS ONE

Journal requirements:

1. When submitting your revision, we need you to address these additional requirements.

Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. Thank you for stating the following in the Acknowledgments Section of your manuscript:

“We would like to thank Ms. Francesca Gieru´c and M. Mathias Delahaye for their invaluable contributions. This work has been supported by the SNFS project ’Immersive Embodied Interactions’ grant 200020 178790.

We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form.

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows:

“T.P

This work has been supported by the SNFS project 'Immersive Embodied Interactions' grant 200020_178790.

Swiss National Science Foundation:

https://www.snf.ch/en

NO: The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.”

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

3. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide.

4. Please include your full ethics statement in the ‘Methods’ section of your manuscript file. In your statement, please include the full name of the IRB or ethics committee who approved or waived your study, as well as whether or not you obtained informed written or verbal consent. If consent was waived for your study, please include this information in your statement as well.

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

Additional Editor Comments:

Please read carefully the remarks of the reviewers and take care of the minor issues.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

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

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

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

Reviewer #1: Yes

Reviewer #2: Yes

**********

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

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: Yes

**********

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

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This paper reports an experiment where different configurations of the real and virtual arm in outstretched position are examined for their effects on body ownership of the virtual body. The experiment is well described and the statistical analysis is excellent. There are a few points that could improve the paper.

Although the submission form states that the data is fully available, I could not see where this was indicated in the paper - i.e., from where the data can be accessed.

In 'Equipment and software' please give the weight of the head mounted display.

In the next paragraph it is not clear whether it is only the virtual hand that holds the cylinder or whether subjects were also holding a cylinder. This seems to be cleared up later in the figure caption - that they were actually holding the cylinder. Was the cylinder tracked, or were transformations to the cylinder computed from transformations to the hand orientation and translation?

Some of the English reads a bit strangely and the paper should be thoroughly checked for this. For example, "All subjects have been through the two blocks" rather than "All subjects completed the two blocks".

"Although this question directly addresses only body ownership, it aims at informing on the impact of the articular limit on embodiment."

" ... at informing on ..." doesn't seem to be a correct formulation.

"subjects shall experience a strong sense of agency for the avatar's movements" in the discussion - the "shall" makes it seem like an imperative.

Figure 5 - the questionnaire scores run from 0 to 1 but the vertical axes extend to 1.4. This is confusing and must be corrected. I think that all the significance *s above the bars need to be pruned, there are too many and the graph becomes difficult to read. Please only include the critical ones that relate directly to the hypotheses.

From the graph it is clear without any significance tests that the critical impact is associated with "Negative Distortion Fully Extended" and "Positive Distortion Fully Extended" which both result in an obvious reduction in body ownership compared to the others. All of the others, even though there may be some significant differences between them, show relatively high levels of body ownership. So "fully extended" with any kind of distortion leading to lower body ownership is the main finding. Although there are differences between the other conditions can the authors please mention also the effect sizes of these differences rather than only significance levels.

In the Results first paragraph I think it would be helpful to readers to first discuss the findings from the graphs in terms of what seems to be greater than what before rushing into discussion of significance levels without explaining what these mean. E.g., we can be told that "x is significantly different from y" without knowing whether this indicates whether x > y or y > x. So it may be preferable to give the latter information first, and then discuss the significance.

In the discussion it says that "subjects severely reject a discrepancy between their own body". But looking at the raw data 'severely reject' seems to be an over statement. It seems that only in the case of "fully extended" with any kind of distortion is there a clear drop in body ownership compared to the other conditions. All of the others are way above the 0.5 mark on the questionnaire scale.

In the discussion "subjects might be more willing not to notice the distortion" - "willing" makes it seem like this is a conscious deliberate choice on the part of the subjects.

Overall this is an excellent and useful contribution to the area of virtual embodiment, and will be important for researchers in this field.

Reviewer #2: The manuscript is well written and the study design is well done. The results from this study can be helpful for conduction virtual reality expriments with healthy and clinical populations including embodied conditions. However the authors should consider some aspects for improving the quality of the manuscript.

- Introduction section:

line 3: add a reference aafter SoE.

Suggestion for improving definitions of self-location, agency and body ownership:

Sense of Self-location: Self-location is a determinate volume in space where one feels to be located. Normally self-location and body-space coincide in the sense that one feels self-located inside a physical body (Lenggenhager, Mouthon, & Blanke, 2009).

Sense of Agency: The sense of agency refers to the sense of having ‘‘global motor control, including the subjective experience of action, control, intention, motor selection and the conscious experience of will’’ (Blanke & Metzinger, 2009, p. 7).

Sense of Ownership: Body ownership refers to one’s self-attribution of a body (Gallagher, 2000; Tsakiris, Prabhu, & Haggard, 2006).

Third pagraph: the authors say 'we identified a relatively frequent problem likely to interrupt the

visuo-proprioceptive integration' ,where you identified this problem? Is there any study arguing this situation? If yes, please cite it.

End of the 4th paragraph: I agree with the impact of internal haptic feedback on movement perception in VR, however the authors should consider that if reserachers provide strong sense of agency making participants actively participate in the initiation of the virtual body movement or vistual body action, this may descrease or delete the mistmatch conflicts, and providing synchronous visuo-tactile correlations. See Kokkinara, E., Kilteni, K., Blom, K. J., & Slater, M. (2016). First person perspective of seated participants over a walking virtual body leads to illusory agency over the walking. Scientific reports, 6

Participants section: not controlling the dominance laterality should be added as a limitation of the study. Even though the difuclty of the task, the joint receptors of the participants will be more sensitive, it should be a higher proprioceptive sense in the dominant upper limb compared to the non-dominant upper limb.

Discussion: the authors should consider that there are evidence showing that it is poosible to provide a distorted fedback of the virtual arm, such as an hyperextension of the upper limb, while providing synchronous multisensory correlations (e.g visuo-tactile feedback), and participants reported higher levels of wnership toward such distortion:

- Kilteni, K., Normand, J. M., Sanchez-Vives, M. V., & Slater, M. (2012). Extending body space in immersive virtual reality: a very long arm illusion. PloS one, 7(7), e40867.

Further, other studies showed that it is possible to provide body ownership illusions toward virtual bodies with distorted positions while providing synchronous visuo-tactile or visuo-motor correlations:

-Bergström, I., Kilteni, K., & Slater, M. (2016). First-person perspective virtual body posture influences stress: a virtual reality body ownership study. PloS one, 11(2), e0148060.

- Matamala-Gomez, M., Nierula, B., Donegan, T., Slater, M., & Sanchez-Vives, M. V. (2020). Manipulating the perceived shape and color of a virtual limb can modulate pain responses. Journal of clinical medicine, 9(2), 291

Avatar representation section: Change the format about the take a home message. I suggest the authros to re-formulate a sentence as an statment.

Conclusion section can be shortened.

**********

6. PLOS authors have the option to publish the peer review history of their article (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 #1: No

Reviewer #2: Yes: Marta Matamala-Gomez

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Reaching articular limits can negatively impact embodiment in virtual reality.

PONE-D-21-23301R1

Dear Dr. Porssut,

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.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Imre Cikajlo, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

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

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

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

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

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

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

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

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: (No Response)

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (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 #1: No

Reviewer #2: Yes: Marta Matamala-Gomez