PONE-D-23-39116The speed of sight: individual variation in critical flicker fusion thresholdsPLOS ONE

Dear Dr. Haarlem,

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Reviewers' comments:

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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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Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

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Reviewer #1: This manuscript provides a succinct and skilfully crafted analysis of individual variations in critical flicker fusion frequency thresholds. Three distinct protocols were executed, and the ensuing results are meticu-lously presented, accompanied by judicious statistical analysis.

Below, you will find some minor comments for your consideration.

Minor comments:

l. 59: may be mention: Muth T et al, 2023

l. 99: ECTS, meaning what?

l. 105: a photograph or a schematic with detailed description would be helpful for the less informed reader. Please, add size of the light source.

l. 115: Protocol. Participants were standing / sitting? Height of tubing was adjustable?

l. 115: tests were performed in the morning or during the entire day?

l. 150: QQ-plots?

l. 155: Pls, explain meaning of 0.8. Is there a graph?

Reviewer #2: The authors did a great job at comparing different methods of determining CFF thresholds, considering individual and group variability. Given the relatively widespread use of the flicker test and the lack of unified paradigms between studies, I think the manuscript is an interesting contribution to the current state of knowledge. The authors rightly pointed out the problem associated with the long time duration of the method of constant stimuli, which would be difficult to apply in some conditions, such as hyperbaric conditions.

The description of the methods is sound. Taking repeated measurements at a similar time of day for each participant is clearly an advantage of the study. The manuscript may benefit from adding of more precise information about the hours of the study.

Statistical analyses are presented in a sound manner, but I suggest adding a brief note about the "car package" from R (line 148/149), explaining that it is a set of functions and tools for regression analysis.

I also recommend moving the description of normality in the results section to the very beginning, before the description of correlations to improve the readability of the description and justify the use of parametric tests.

The created graphs are readable, but I think the data presented in Figure 1 would be more easily compared visually after using the same reference points on the x and y axes.

Description of Figure 3 - please standardize the lowercase and uppercase letters in the statistics given.

In the discussion section, the authors describe factors that may affect the differences in CFF thresholds. I agree that they may be related to neuroanatomical, neurophysiological and neuropsychological factors. Have previous studies compared genders or age groups in this regard? I lack such an explanation.

It is not clear what the authors meant when they wrote about testing visual temporal resolution among humans in real-world conditions (line 292-294). I suggest adding a clarification.

In summary, I think the manuscript will be suitable for publication after making minor revision.

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Reviewer #1: Yes: Prof. Dr. Jochen D Schipke

Reviewer #2: Yes: Natalia Daria Mankowska

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The speed of sight: individual variation in critical flicker fusion thresholds

PONE-D-23-39116R1

Dear Dr. Haarlem,

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.

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Kind regards,

Christopher Nice, Ph.D.

Academic Editor

PLOS ONE

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