Review History


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Summary

  • The initial submission of this article was received on February 23rd, 2017 and was peer-reviewed by 2 reviewers and the Academic Editor.
  • The Academic Editor made their initial decision on March 25th, 2017.
  • The first revision was submitted on April 25th, 2017 and was reviewed by 2 reviewers and the Academic Editor.
  • A further revision was submitted on May 15th, 2017 and was reviewed by the Academic Editor.
  • The article was Accepted by the Academic Editor on May 17th, 2017.

Version 0.3 (accepted)

· · Academic Editor

Accept

I have read through your reply to the reviewer's comment and your revised manuscript. I am satisfied with your response and decided that there is no need to send to the reviewer. You and your coauthors have my congratulations. Thank you for choosing PeerJ as a venue for publishing your research work and I look forward to receiving more of your work in the future.

Tsung-Min Hung, Ph.D.
PeerJ editor
Distinguished professor
Department of Physical Education
National Taiwan Normal University

Version 0.2

· · Academic Editor

Minor Revisions

I have now received two reviewers’ comment and both reviewers were generally satisfied with your reply and revisions from previous comments. However, one reviewer has pointed out some minor editorial issues that require your additional attention. Please address these issues then I'll accept your manuscript.

Tsung-Min Hung, Ph.D.
PeerJ editor
Distinguished professor
Department of Physical Education
National Taiwan Normal University

Reviewer 1 ·

Basic reporting

I have only a few very minor editorial comments:
(NOTE: I am using the line #’s with the track changes still “on” and with none of them accepted.
Line Comment
39 Add “related” after “positively”
57 Replace & with ‘and’
180 I think you need to modify this to say “on the left. They then pressed the ‘1’ or ‘3’ key with their left or right index finger, respectively, to indicate if the matrix was or was not a match, respectively”. Without this, it isn’t clear if 1 still means m

Experimental design

The authors have appropriately addressed previous concerns that were pointed out.

Validity of the findings

The authors have appropriately addressed previous concerns that were pointed out.

Comments for the author

I would like to congratulate the authors on making very appropriate revisions to an already strong paper. The manuscript is now more clearly positioned in terms of how it adds to the literature (i.e., relative to sex differences and relative to the use of a cross-sectional design). It has been a pleasure to review these authors work and I sincerely applaud them for their thoughtful and appropriate responses to the criticisms initially raised.

Reviewer 2 ·

Basic reporting

Everything is fine.

Experimental design

Everything is fine.

Validity of the findings

The authours have revised manuscript appropriately and clearly.

Comments for the author

Congratulate to the authors on making a high-quality paper.

Version 0.1 (original submission)

· · Academic Editor

Minor Revisions

I have received two reviewers' comments. Although there are some merits in your manuscript, several aspects of this manuscript should be revised to improve its clarity. Their observations are presented with clarity so I'll not risk confusing matters by belaboring or reiterating their comments. While I might quibble with the occasional point, I note that I regard the reviewers' opinions as substantive and well-informed. I believe that all of the highlighted reservations require contemplation and appropriate attention in revising the document if it is to contribute appropriately to PeerJ and the extant literature.Please revise or refute according to the two reviewers' comments and provide a point by point reply in addition to the revised manuscript.

Tsung-Min Hung, Ph.D.
PeerJ editor
Distinguished professor
Department of Physical Education
National Taiwan Normal University

Reviewer 1 ·

Basic reporting

No comment. All is fine.

Experimental design

All is good, except for the inherent limitations of using a cross-sectional design. In my opinion, this study still advances the literature, but it is critical that the authors appropriately handle this limitation in their manuscript. I offer suggestions in my general comments.

Validity of the findings

I point out several places where the authors speak "beyond" their results by using causal language to describe their correlational findings and implications. Otherwise, all is good.

Comments for the author

General Comments
1. Abstract – the Methods information needs to be written in more than one sentence. This is a run-on and is unclear.
2. Lines 44-45: Lack of PA only leads to decline in cognition with advancing age. This is not true generally.
3. I appreciate that in the introduction, you have made the case that it is important to understand which aspects of working memory are most impacted by physical activity. That being said, the primary limitation of your study is the use of a cross-sectional design. I think this needs to be addressed in the introduction. In particular, I think that your work would be more well-justified if you put it into context and specifically argued for the need for this type of study as a first step. In the absence of you arguing for the value of a cross-sectional study, I feel like the limitations outweigh the advancements to our understanding.
4. Lines 184-187 – this is not written clearly and could be improved by describing the differences in order from the faster RT to the slowest (or vice versa).
5. Given that none of the interactions involving sex were significant, Figure 4 should not be included.
6. I do not think the correlational analyses add anything to your paper. I would suggest removing these from the paper.
7. I noticed that although not significant, differences in performance on the SST were in the same direction as observed for the MRT. Thus, I wonder if your data are really strong enough to draw the conclusion that the differences in VST are solely due to differences in MRT. I have two statistical questions I would like you to consider and respond to:
a. The assumption of homogeneity of variance appears to be challenged for the VST RT data and, to a lesser extent, by the MRT data. For VST, the standard deviation for the LG group is more than twice that of the HG group. For MRT, the SD is almost 1.5 times bigger. As such, I am concerned about the results of the ANOVA (particularly for VST). Is this something you can address?
b. I like your idea of parsing working memory into two components to understand better how PA relates to these aspects of working memory. But, would it be possible to use performance on the SST and on the MRT as a predictor of performance on the VST? In other words, how strongly related are these tasks in terms of performance?
8. In the discussion (line 239 and line 259) you say that those in the HG group had “better” visuospatial working memory. But, there were no differences in response accuracy. So, it seems that it would be more accurate to say that they performed faster. Later (line 262), you say that their performance was “superior”. Again, it wasn’t superior, it was only faster. This is important from the point of view of being careful with word choice, but it’s also important conceptually for two reasons.
a. Your results essentially show that the HG is faster than the LG group. This seems to emphasize the short-coming of the study which is the correlational design. Isn’t it equally plausible that people who perform faster are, therefore, attracted to physical activity? I believe this needs to be considered in the discussion.
b. Equally important, although significant differences were only observed on the more complex tasks and you interpret this as being consistent with past literature, another explanation of your results is possible. That is, as has been argued by Salthouse and others, perhaps the potential benefits of PA are only apparent for speeded tasks and it is this faster response speed which then benefits higher order cognitive performance. In other words, perhaps the HG group is not actually “better” at rotation, but because they are faster, that allows them to perform better on the VST.
9. In several places, you use words that suggest causation when you should only be talking about relationships.
a. Line 32-34 – Please don’t use “benefits” or “benefit”
b. Line 197 – please do not use the word “promotes”
c. Line 257 – please don’t use “benefited”
d. Line 266 – please don’t use “effect”
e. Line 271 – please don’t say “did not benefit from”
f. Line 301 – please don’t say “selectively benefited”
g. 306-307 – your data do not support this conclusion.
10. When you say that you analyzed the “temporal” phases, is that really correct? Do they necessarily happen in a precise chronological order or is it more about both aspects of working memory needing to be achieved? I know you used “stages” in the intro, so maybe these do always occur in a particular order, but please be clear on this throughout.
11. Throughout the paragraph from lines 264-, I would suggest adding the word “significant” for those differences that were statistically significant. This is because there were observed non-significant differences between HG and LG for RT on the SST and the magnitude was not trivial (mean diff = 65 msec). Out of curiosity, I put the observed effect size for SST between groups (d=(700-634)/94)=0.70) into GPower and found that the required sample size with alpha=0.05 and power=0.80 was 54. Given that you had a sample size larger than this, that makes it seem as if this effect actually should/could have reached statistical significance. I don’t doubt your results and forgive my naivete about how this might impact your ANOVA, but I wonder if the statistical power for the main effect for group was impacted by the fact that this was tested in a 2x2 ANOVA? In any event, I think it might be premature to conclude that the effects of PA are most likely to occur on the manipulation portion rather than the storage portion.
12. Lines 285-290 – please omit this paragraph as I do not think it adds to your paper.
13. Lines 295-297 – I think they might also be due to a relatively small sample size.

Reviewer 2 ·

Basic reporting

no comment

Experimental design

no comment

Validity of the findings

1. The findings were generally valid. My main concern here relates to the conclusions made by the authors in terms of interpretation of the results. For example, line 264-279, the result shown HG responded faster than the LG on the online mental manipulation task (MRT), and author explain this finding as supportive of the idea that PA selectively improves cognitive function requiring higher cognitive demands rather than on the short-term memory task (SST). I would suggest authors can provide more discussion beyond this point and to emphasis your selective and task-specificity effect of PA on cognitive function.
2. Line 280-285, again, the finding didn’ t show any sex difference and thus didn’ t support the hypothesis. Authors implied that it’s because of the lower number of females than males participants. Can author provide any evidence to back up this explanation? Indeed, a much broader perspective should be taken for this discussion to be really interesting, beyond the very factual elements that are given in the present version of the manuscript.

Comments for the author

The purposes of the study were three folds. First, to verify the relationship between physical activity (PA) and visuospatial working memory; second, to determine whether one or both stages of the visuospatial working memory were affected by PA: third, to investigate sex differences. Although generally the manuscript was well written and the conclusion seems supported by their data, there are some issues need to be addressed before the manuscript can realize its potential to contribute to the extant knowledge base between physical exercise and cognitive function.

General comments

Introduction
1. In the second paragraph of the Introduction, the author tried to emphasize participation in PA leads to better verbal working memory. Here bring two questions: first, authors argued that studies only tested storage processing with a low load of active manipulation processing. However, what is the strength of this study, compared to previous studies, should be provided. Second, Authors hypothesized that participants who were classified as more physically active would exhibit superior general visuospatial working memory task performance and that PA would thus be significantly associated with the performance of at least one of the processing stages. Nevertheless, what is the rationales for this hypothesis should be elaborated.
2. One of the purposes of this study was to compare the sex difference in visuospatial processing and authors expected that the group comprising men with the higher PA would show better visuospatial working memory in general. Again, from the introduction, we can’t tell why author makes this hypothesis. The author should explain more in depth.

Method
1. In the task section, more details such as how long for the response window, how participants make a response, one hand or two hands should be provided.

Discussion
1. In general, the discussion is very descriptive and does not interpret the findings within a theoretical framework (Please check if your intended meaning was retained).
2. The limitation of subjective measurement for the level of physical activity (i.e., IPAQ) should be discussed and more objective measurement for the quantification of physical activity such as accelerometer could be suggested for future studies.
3. Line 273: “Storage processing as examined in the SST reflected….”, please add references for this statement.

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