PONE-D-20-07425

Two halves are less that the whole: evidence of a length bisection bias in fish (Poecilia reticulata)

PLOS ONE

Dear Mrs. Santacà,

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.

So far I have had the manuscript reviewed by one expert on animal illusion perception. This reviewer supports the publication, but also raises a number of important revisions. I have read and agree with R1. In particular, I think you must more fully review animal literature on illusions, and hence reduce claims of this study being first evidence of a length bisection bias in an animal species. I also think there is a broader literature on spatial illusions like the  Delboeuf illusion in animals that could be discussed. Please carefully address each point. I would also like that you make raw data available (see PLOS policies). If you can make all revisions in a careful way, I may proceed on the basis of the advice of the one expert reviewer.

We would appreciate receiving your revised manuscript by May 30 2020 11:59PM. When you are 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.

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To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

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). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

Adrian G Dyer, Ph.D.

Academic Editor

PLOS ONE

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2. Please update the word "that" in the title to "than" for grammatical correctness.

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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?

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

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

Reviewer #1: Yes

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Reviewer #1: No

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

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Reviewer #1: Yes

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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: The authors studied the HV visual illusion in guppies. They found that guppies were susceptible to the illusion when a line bisected the horizontal line - but this was not the case with 'L-shaped' stimuli. I would recommend this manuscript for publication with some minor revisions:

1. The authors state that there are some restrictions on data availability. Is this necessary? Why can the data not be publicly accessible?

2. The title has an grammatical error. It currently reads: "Two halves are less THAT the whole: evidence of a length bisection bias in fish (Poecilia reticulata)". I think the authors meant to write: "Two halves are less THAN the whole: evidence of a length bisection bias in fish (Poecilia reticulata)"

3. Line 15 - "explores" should be "explore".

4. I am confused by the claim the authors make multiple times (e.g. line 25-26 "... providing the first evidence of a length bisection bias in an animal species." I thought that this has been shown in non-human primates and hens? If this is the case, the lines and the other claims like it throughout the manuscript should be removed.

5. Line 144 - "breed" should be "bred".

6. Line 227 - "subjects" should be changed to "subject" as the authors state that only one guppy took the 120 trials instead of the 24 trials of the other 11 guppies.

7. Lines 258-260 - The first sentence of the discussion is messy and should be revised. The second part of the sentence does not make sense: "... that the results of which experiment have the capacity to shed light on the evolution of perceptual mechanisms underlying size estimation of vertebrates."

8. Line 258 - "is susceptible" should be changed to "are susceptible" for grammar purposes.

9. Line 270 - Change "human" to "humans".

10. Line 270 - Change "primate" to "primates".

11. 270 - delete the word "so".

12. Lines 280-284 - This is a very long sentence and should be broken up and made clearer. Currently it is confusing. The Delboeuf illusion should also be explained better for readers to understand how/why humans perceive it in a certain way and how/why guppies perceive it differently.

13.

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Reviewer #1: No

[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 to be viewed.]

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 us at figures@plos.org. Please note that Supporting Information files do not need this step.

PONE-D-20-07425R1

Two halves are less than the whole: evidence of a length bisection bias in fish (Poecilia reticulata)

PLOS ONE

Dear Mrs. Santacà,

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.

I have carefully read the revised manuscript which I find very interesting. I have however two suggestions that I think would improve the manuscript for readers.

AGD1 Given the size of the Sup Table S1 containing the data requested by reviewer 1 (and myself to be compliant with PLOS1 policies) is not very large, I would like to suggest you just add this table to the main mainscript so that all information is at hand for readers of the manuscript. Else if you want to retain this information only as sup file I think it would be good to label that file so that when it is downloaded it is clear what the information relates to. But as stated above, if the information is placed in the main manuscript for readers and clearly labled it might be best? I will leave this decision to you.

AGD2 Regarding your revised text ["In the latter case, guppies showed not to overestimate the size of a circle presented in a small circumference. On the contrary, they demonstrated to underestimate the size of such circle and to overestimate the size of the same circle but presented in a large circumference suggesting a reverse perception of the Delboeuf illusion compared to humans [19]."]. I found this section of text not very clear. Do you mean [guppies showed evidence of not overestimating size.....]? I found the logic of these 2 sentences difficult to understand as written; can you please re write and cross check with lab members so we are confident that the general readers of PLOS will easily understand you meaning?

If you can attend to these two points I am confident I will be able to accept the manuscript.

We would appreciate receiving your revised manuscript by Jun 12 2020 11:59PM. When you are 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.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

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). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

Adrian G Dyer, Ph.D.

Academic Editor

PLOS ONE

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

[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 to be viewed.]

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 us at figures@plos.org. Please note that Supporting Information files do not need this step.

Two halves are less than the whole: evidence of a length bisection bias in fish (Poecilia reticulata)

PONE-D-20-07425R2

Dear Dr. Santacà,

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

Within one week, you will receive an e-mail containing information on the amendments required prior to publication. When all required modifications have been addressed, you will receive a formal acceptance letter and your manuscript will proceed to our production department and be scheduled for publication.

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If your institution or institutions have a press office, please notify them about your upcoming paper to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, you must inform our press team as soon as possible and 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.

With kind regards,

Adrian G Dyer, Ph.D.

Academic Editor

PLOS ONE

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