PONE-D-21-10206

Influences of time of day on generalization

PLOS ONE

Dear Dr. Tandoc,

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. In addition to the comments from the reviewers, I have additional suggestion for you to consider. Given that a significant portion of this research specifically focused on the impact of sleep on generalisation, it would be advantageous if the title was modified to include sleep and not just time-of-day. 

Please submit your revised manuscript by Jun 19 2021 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: http://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,

Bradley R. King

Academic Editor

PLOS ONE

Journal Requirements:

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

1) 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) Please modify the title to ensure that it is meeting PLOS’ guidelines (https://journals.plos.org/plosone/s/submission-guidelines#loc-title). In particular, the title should be "specific, descriptive, concise, and comprehensible to readers outside the field" and in this case it is not informative and specific about your study's scope and methodology.

3) Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.

[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: Partly

**********

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

Reviewer #1: Yes

Reviewer #2: No

**********

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

**********

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: Yes

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 is a very long, complex paper which uses a very complicated task to assess whether or not and to what degree people generalize from exemplars. It provides, across a series of studies, a reasonably clear message about sleep (it doesn't seem to influence generalization) and a somewhat less strong message about time of testing (there is greater generalization in the morning than in the evening). The authors do an excellent job of explaining their complex patterns of results and make clear the connections to existing literature (i.e., the references and the explanations) are excellent. The discussion is particularly strong and may well be influential for subsequent work.

what would have made this paper a better paper? If it were possible to focus/limit analyses to DVs relevant to generalization, it would have been a far easier read, especially given the large number of studies included. On the other hand, this is an extremely honest paper which allows readers to see warts in the research process.

Reviewer #2: This study investigates a very interesting phenomena, (specifically, generalization of newly acquired memories) that sleep would appear to be a likely candidate to facilitate/support/enhance. The inclusion of a nap control experiment provides valuable insight, and is something that is not normally part of experimental designs that include sleep, so this welcome addition allows for valuable comparisons between a night of sleep and a nap. Along the same line, additional behavioural experiments to further prole time of day add rigor to the overall report, despite that some effects were not easily replicated, highlighting the inherent complicated nature of studying this phenomena and the pitfalls of overlooking time-of-day effects.

Major comments:

1. One of the main conclusions is difficult to support based on the approach and outcomes, specifically, statements such as: “…suggesting a role for circadian rhythms apart from sleep”. It cannot be determined if circadian rhythms, per se, or other factors linked to time of day, or time elapsed between test and retest explain the effect of time on generalization. This conclusion is also not supported by / consistent with the analyses on chronotype. Suggest removing this or modifying these statements to be more in line with the study design and results.

2. Another main conclusion: “…a state of lowered inhibition in the morning may facilitate spreading activation between otherwise separate memories…” is difficult to substantiate, as “inhibition” was not directly measured in the current study. Suggest framing this more as a possibility to be investigated in the future, rather than an interpretation that can be made from the current study.

3. Null results are difficult to interpret; for which there are many across the series of Experiments. It would be helpful to get a sense of whether the null findings were due to insufficient statistical power, re; ~ 15/group is common in the literature, but often questionable whether sufficient to detect variable/subtle behavioural effects. If power analyses were conducted, they should be presented, otherwise, it would be helpful to know if the study was adequately powered. The pooled analysis presented in Experiment #7 partly speaks to this issue, but not expressly for each individual experiment.

4. In Experiment #1, several correlations between outcome variables were performed, however, it is not clear how many such analyses were performed, and if this was done in any systematic/parsimonious manner and seem overly exploratory the way they are presented. Multiple comparisons may be an issue if many analyses were conducted without any correction. This also applies to subsequent experiments.

5. There are a large number of experiments presented, with similar, but not exactly the same analysis strategies employed, with a very large number of null results presented alongside significant findings. It is easy for the main message to get buried in all this. Summary tables of results might help with the presentation.

6. The conclusion (albeit stated as exploratory), that the “lack of replication of the time of day effects in Experiment 7 may be due to this cohort of participants taking the task less seriously” is unfounded. How was the “seriousness” of the participants ascertained?

Minor comments:

1. While the initial aim of the first 3 experiments was to investigate sleep, and the hypotheses are presented only very briefly in the introduction. The subsequent studies were designed to investigate why no effect of sleep was observed. The Introduction could benefit from presenting specific hypotheses for the subsequent studies.

2. How many participants reached the 1-hour cut-off for the training phase? Performance in the case where they were cut-off due to the time limit may be interpreted differently than those who completed the training in the allotted time.

3. Partial credit on the RAT was given using Levenshtein distance, which is innovative, but perhaps not appropriate, given that the goal of the task is not to assess spelling/typographical errors. i.e., this measure confounds semantic accuracy with typographical precision (which is not of interest in this case). It might be more appropriate to instead manually assess whether errors were typographical, in which case, effectively the correct word (full points), or an incorrect word (no points). If a large number of responses were partial scores, and if in most cases the Levenshtein distance is neither close to a full point nor zero, then this may be problematic. By contrast, this may not be an issue for the priming score in the distractor priming task, re; lexical accuracy is relevant in that case.

4. The results of the earlier experiments were not replicated, which was attributed to the changes in the task design. This is intriguing as it would suggest some sort of dose-response relationship for the shorter version. Suggest mentioning this possibility in the Discussion.

5. The Discussion is very long, particularly given that there are already “interim” discussions for each experiment, and also in light of the large volume of null (and somewhat inconclusive) results. Suggest significantly shortening this section to summarize the main message.

**********

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: 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.]

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.

Examining the effects of time of day and sleep on generalization

PONE-D-21-10206R1

Dear Dr. Tandoc,

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,

Bradley R. King

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 #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 #2: Yes

**********

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

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 #2: (No Response)

**********

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 #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 #2: The authors have done a commendable job in replying to all of the comments made in the first round of revision.

**********

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 #2: No