PONE-D-22-31727Putting People in Context: ERP Responses to Bodies in Natural ScenesPLOS ONE

Dear Dr. Balas,

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.

Two expert reviewers have evaluated your study. Both reviewers found your work interesting and well executed, but both also raise important points that need to be addressed. Reviewer 1 in particular notes the lack of a control category, and both reviewers ask for important clarifications regarding the methods and the interpretation of your results. The reviewers also provide helpful and constructive suggestions to address these points, so I believe it should be possible for you to successfully address all the reviewer comments, and I look forward to receiving your revisions. 

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Academic Editor

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?

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

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

Reviewer #1: Yes

Reviewer #2: Yes

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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: Yes

Reviewer #2: Yes

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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

Reviewer #2: 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: Review of PLOS ONE 22-31727

This paper presents two EEG studies investigating the effect of body inversion on the previously reported body-selective EEG component (N190). The focus is on how the inversion effect is influenced by the number of bodies (Exp 1) and the presence of scene background (Exp 2). The studies are well-conducted and address novel questions. The paper is also easy to follow. However, I have several major concerns:

-The study did not include a control category. This makes it difficult (if not impossible) to directly compare the N190 amplitudes across stimulus conditions because the evoked response between 140-216 ms (taken as the N190 here) will be affected by any difference in visual input. For example, the difference between bodies with vs without background could be driven by the background itself. Similarly, the difference between one vs multiple bodies could be driven more generally by increased clutter. For this reason, the main comparisons in the manuscript could focus on the inversion effect, and how this inversion effect differs across conditions. I would encourage the authors to make this focus clear from the beginning (starting with the hypotheses) and avoid comparing responses across categories as these may not be related to body processing as such.

-The definition of the N190 (e.g., 140-216 ms) was not sufficiently motivated. The text states that this was based on inspection, but it is not clear what exactly determined this precise time window.

-Because there was no control category, it is unclear whether the N190 (as defined here) was body selective and corresponded to the previously reported body-selective N190 (e.g., Thierry et al., 2006; Taylor et al., 2010). Please comment on the correspondence of the N190 here and in previous reports, both based on selected electrodes and definition of time window. Ideally, additional analyses would be included that more closely follow the N190 as defined previously, particularly because results are not always in line with previous reports.

-The sample size (N=16) is on the low end for today’s standards. Please provide information about how the sample size was determined (e.g., was a power analysis conducted?).

-How was inversion achieved? Were the images rotated by 180 degrees? Please include the inverted versions in the stimulus example figures (Fig 2 and Fig 6) so that it is immediately clear what the main manipulation was. Did the conditions differ in the visual field that was stimulated (e.g., Exp 2: upright: most of the body in lower visual field, inverted: most of the body in upper visual field). If so, could that explain the differences between the effects observed here and in previous literature?

-Some papers that may be relevant to cite or discuss:

Related to the neural basis of body and face perception:

FFA: Kanwisher et al., J Neurosci 1997; EBA: Downing et al., Science 2001; FBA: Peelen & Downing, J Neurophys 2005

Related to the body-selective N1:

Gliga & Dehaene-Lamertz, J Cogn Neurosci 2005; Pourtois et al., Neuropsychologia 2007; Taylor et al., Brain & Cogn 2010

Related to body processing in natural scenes:

Bindemann et al. JEP:HPP 2010; Kaiser et al., J Neurosci 2016

-Please provide the behavioral results (accuracy and RT) for both experiments; did these differ across conditions?

-When reporting the statistics, please also report the non-significant interactions that are relevant to the research question (e.g., on p.16, the interaction between orientation and numerosity).

-For the Latency analysis, please provide the means, either in the text or in a figure (e.g., in the format of Figure 3, possibly as panel B in that figure; same for Experiment 2).

-For the decoding analysis, it was unclear why such a long time-window was included (up until 1s after stimulus onset). This time window presumably includes the response of the participant, which was directly reflecting stimulus orientation. Considering that the focus of the study is on the visual processing of bodies, I would limit the time window to the visually evoked response (e.g., 0-400 ms).

-The significant interactions (e.g., on p.29) should be followed up by additional tests (e.g., separate 2x2 ANOVAs or pairwise t-tests) to interpret these interactions. For example, for the data shown in Fig 8 it is not clear which differences drove the 3x2 interaction.

Minor:

-p.7: “affects of wider-ranging” --> “effects of wider-ranging”

-Fig 1: The examples stand out in not showing the inner facial features of the people. Was this on purpose, and true for most of the images in the database, or was this specific to these examples?

-The beginning of the Results section (about preprocessing etc.) would fit better in the Methods section.

-p.14: Please provide the correspondence between the electrode numbers and standard electrode labels; e.g., did these include P7/P8?

-Fig 2 and Fig 7 miss y-axis legends and legends for the conditions (colored lines). The x-axis is hard to read, also because there is no clear 0 point. It would be informative to indicate the N190 window using shading or similar.

-Fig 2 legend “This data is” --> “These data are”

Reviewer #2: In this paper, the Authors explore how the N190 (ERP component related to body processing) is affected by several, previously unexplored, aspects related to person perception, generally linked to the stimuli’s ecological validity (few/multiple bodies – presence of a real world scene in the background). While in terms of results there are some limitations (due for example to the inconsistency of results related to inversion effects between experiment 1 and 2, and previous literature), the Authors take careful/appropriate conclusions based on their findings. Indeed, natural appearance of the body “in the wild” seem to matter for the N190 amplitude, and for decoding accuracy in general. A side conclusion is also that the N190 cannot be fully accounted for by low-variability within the stimuli set as argued in the past (Thierry et al., 2007).

I think that the manuscript is overall well written, particularly in the intro and discussions, and I enjoyed reading it.

However, I think the paper would benefit with some revisions:

Could several of the effects observed on the N190 be accounted by attentional deployment to body stimuli, rather than some genuine differences due to configural processing? – For example, N190 was smaller (more negative) with multiple people, and more positive with upright stimuli (as opposed to inverted). Both conditions more than one person, and the “weirdness” of an inverted body, supposedly increase the likelihood that someone would gaze to a body/person within a scene, therefore influencing the N190. Generally, it would be useful if in the results the Authors were also consistent using “more negative” or “more positive” – see also points below.

Is that the case that the Authors expected an interaction with the effect of one – to – many people modulating the N190 as a function of inversion? Seems so from what stated in the abstract. If that is the case, could the Author explain why such interaction might be expected?

Hemisphere by orientation interactions (both in experiment 1 and 2) – I found these interactions quite intriguing because if inversion affects configural processing, then inverted stimuli body part-based processing should be increasing. Single body part processing seems to rather involve more the left hemisphere (Urgesi et al., 2007; Bracci et al., 2012). Here you instead stronger inversion effects on the right, perhaps reinforcing the interpretation that in the case of the N190 the inversion effect is rather explained by domain general attentional effects rather than configural processing as such.

I found the results of the classification analyses a bit hard to read. Is quite clear what you did – but less clearly written the conclusions you take from them. For example, in the abstract you mention that orientation decoding is also contributed later (after 300ms). However, this is not clearly shown in the result sections. I appreciate the figure 4a and 4b such that all the electrodes can be seen, however, it would be important perhaps also to show a line graph with decoding accuracy on the y axis and time in the x axis across all the electrodes (and/or only taking the electrodes of interest, e.g. those of the N190 or all the posterior electrodes?). In this way would be clearer the “when” of orientation/numerosity/appearance classification reaches significance against chance. Also – do you think would be useful to look at the decoding accuracy of numerosity (exp 1) and appearance (experiment 2), as presented in the figure 4a and 10a without averaging across upright and inverted, and only looking at the upright condition? Of course orientation was task relevant and did not show interactions, but this may be still interesting to look at?

The paper would really benefit with some more detailed data visualization, for example it can be quite confusing, particularly for a non-eeg expert reader, to deal with expressions like “more positive”/”less negative” amplitude in one or the other condition. – see minor points specific on the figures.

Minor:

E1 Stimuli:

Nice database, what is this database usually used for? Computer vision?

In the stimuli example in Figure 1 the face was always non- or barely- visible – is that something that you controlled for, or in some cases the face was fully visible? Would be useful to specify this since, as the Authors acknowledge, that might matter for the inversion effects.

Figure 2 and Figure 7 do not contain any legend for upright and inverted, also is not entirely clear what the y axis represent, because the labels are absent. I am not entirely sure also what was the purpose of showing these figures?

Figure 3 – Would be nice that the figure would be a line plot showing the actual component also, would make the results sections clearer – instead of trying to read through “more negative, more positive amplitude”. Also in the captions it says “across conditions” but it should rather be “in each condition”.

Page 16 – results: Indicate also the contrast between few and many even if it didn’t reach significance; In this section would be also useful to have descriptives related to the differences (Mean values and 95% CIs so that we could make a sense of the extent of the effects.

Figure 4a. is this collapsed across upright and inverted conditions or represent only the upright condition? Seems that there is a typo in the caption.

Discussion Exp 1 and 2: Would be interesting to know whether the inconsistencies between studies on inversion effects affecting the N190 relate to the task-relevance this factor had in the experiments?

Results Experiment 2: N190 amplitude: Please include the relevant contrasts at the end when you break down the two significant interactions.

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Reviewer #1: No

Reviewer #2: No

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PONE-D-22-31727R1Putting People in Context: ERP Responses to Bodies in Natural ScenesPLOS ONE

Dear Dr. Balas,

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. Both reviewers are satisfied with your revisions and have only a few minor remaining comments. In particular, both reviewers suggest including example stimulus figures. Once you address all remaning comments I will assess the revisions myself, likely with no need for further review. 

Please submit your revised manuscript by Apr 20 2023 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,

Guido Maiello

Academic Editor

PLOS ONE

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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.

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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: (No Response)

Reviewer #2: All comments have been addressed

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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: Yes

Reviewer #2: Yes

**********

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

Reviewer #1: Yes

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: Yes

Reviewer #2: Yes

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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: Yes

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: The authors have addressed most of my concerns. However, it seems like the example stimuli figures have been removed in this revision. If at all possible, I would strongly encourage the authors to bring these back in (if the experimental stimuli are not allowed to be reprinted, the authors could create new stimuli that are representative of the experimental stimuli). Seeing the example stimuli (both upright and inverted) for both experiments really helps to understand the manipulation in a single glance.

Reviewer #2: I thank the Authors for better characterising the research question specifying that inversion served as a control for body processing specificity. Generally, I think the paper has improved with the revisions and the conclusions taken are supported by the data.

Minor:

Figure 3a 3b - 10a 10b

Please add labels at the axis (electrode n. and timepoint).

Experiment 2: N190 peak latency analysis - You report a marginal effect, please clarify whether this goes in the same direction of exp. 1 - Seems that it is the case from what I read in the discussions.

I would include inverted stimuli examples in the figures for completeness.

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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.

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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: No

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[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.

Putting People in Context: ERP Responses to Bodies in Natural Scenes

PONE-D-22-31727R2

Dear Dr. Balas,

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.

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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,

Guido Maiello

Academic Editor

PLOS ONE

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