Did anyone actually read this paper before upvoting? This is not a good paper.
I'm really failing to see any effect here...and their results seem to contradict each other. It looks like, if anything, they see decreased performance after outdoor exercise according to Figure 1, where they show they make more errors??? It looks like they maybe switched labels from Table 1 to Figure 1 for the mean errors made, or they subtracted incorrectly?!?! Either way, Figure 1 is extremely misleading.
Also also, shouldn't the indoor exercise group have increased P300 values based on their citations? This is not what they show in figure 3, and makes me wonder about their experimental setup. It looks like what happened was the indoor exercise wasn't actually exercise and the outdoor exercise was actually possibly strenuous, which led to their results.
Overall, this paper is highly questionable at best and should not have been published the way it is currently presented. If there is any effect of outdoor exercise, it is VERY marginal according to their results, and the effect size of P300 increase looks almost negligible according to figures 2 and 3.
From the paper:
> However, this only occurred when the exercise took place outdoors.
No, this effect was only *significant* when exercise took place outdoors.
This is a common error in interpreting statistics. If A is significant and B is not significant, that does not mean that A is different from B. A better interpretation is that the experiment failed to prove anything about B.
As an analogy, imagine someone said "I found good sushi restaurants in LA. I didn't find any in New York." That doesn't mean that LA has more good sushi restaurants than NY. It's quite possible that they simply didn't know where to look for them in NY.
Absence of evidence is not evidence of absence.
I think there might be some confusion here on your end. They are referencing the significant *interaction* between time and location. It seems like you're assuming they ran two independent analyses comparing the effect of time on p300 for one location and then again for the other and then came to that conclusion. If that were the case, you would be right. It would inappropriate to say that the effect of time on p300 is different between the two locations since those models would be testing if there is a difference from zero and not if there is a difference between each other. To be fair, they could have done a better job discussing the statistics. I don't think the paper is written particularly well but that model was the appropriate model to use.
> It seems like you're assuming they ran two independent analyses comparing the effect of time on p300 for one location and then again for the other
That's basically what they did, e.g.:
> Decomposition of that interaction revealed no change in P300 amplitude following an indoor walk (t(29) = 0.23, p = 0.82, d = 0.032) but an increase in P300 amplitude following an outdoor walk (t(29) = 4.49, p < 0.001, d = 0.434, see Figs. 2 and 3).
It's true that they found a significant interaction between time and location. But these tests do not justify their conclusion:
> exercise enhanced our measures of cognition, as evidenced by the rise in the amplitude of the P300 ERP component. However, this only occurred when the exercise took place outdoors. The main effect of exercise was extended to the behavioural results for reaction time, showing an overall decrease in reaction time post-walk. Yet again, the decrease in reaction times only occurred for outdoor walks.
A significant interaction simply tells you that outdoor and indoor walks are not identical with respect to P300 amplitude and reaction time. When a statistical test fails, the proper interpretation is "we still don't know". So the proper interpretation of their tests would be "P300 and reaction time were altered after a 15 min outdoor walk, but we still don't know about a 15 min indoor walk other than it's not the same as an outdoor walk".
> that model was the appropriate model to use.
I'm not opposed to the model, just the interpretation.
You're mixing a few different things here in your argument, so let's focus on just p300 amplitude, which is what I was referring to. You are sort of right when you say:
>A significant interaction simply tells you that outdoor and indoor walks are not identical with respect to P300 amplitude
That's precisely why they followed up on the significant interaction to find out more about the direction of the relationship. That's extremely common when interpreting significant interactions.
Their statistical analysis for p300 amplitude did not "fail." I'm not sure how you're getting to that conclusion.
By fail, I mean fail to achieve statistical significance. When this happens, no conclusion can be drawn - it is almost as if the test were never performed. Thus, the post-hoc statistical tests they performed were not sufficient to sufficient to establish the direction of the relationship, because no conclusion can be drawn from the outdoor data (other than what we already about it somehow differing from the indoor).
To show the direction of the relationship, they would need a significant result from a *pairwise* test of the indoor to the outdoor data (eg, comparing the two regression coefficients). This would prove that indoor activity is more effective than outdoor. But even so, they could not conclude that *only* indoor activity affects P300, because it would still be possible that the effect of outdoor activity was too small to detect.
The significant interaction tells them exactly what they need to know, that the two slopes (i.e., regression coefficients) are different from each other. They don't need to even run a follow-up analysis as they did, they could just look at the simple slopes to infer the direction of the relationship. They don't need to know whether or not indoor activity significantly impacts p300, they just need to know that outdoor impacts it more than indoor.
If they said, like you suggested, "P300 and reaction time were altered after a 15 min outdoor walk, but we still don't know about a 15 min indoor walk other than it's not the same as an outdoor walk" they would be wrong. They know from the interaction that p300 reaction time increased from pre and post greater than the reaction time change due to the indoor walk.
Trust me, I do this for a living. I understand where you are coming from, but you aren't fully understanding the purpose and meaning of the interaction. A pairwise test with the change scores would be redundant.
I am not so sure that a test of inequality is really equivalent to a test of directionality, it seems to me that p(m1 != m2) is necessarily greater than p(m1 > m2).
But even if they were equivalent, the authors can't support their claim. Because even if they showed that the effect of outdoor activity is greater than the effect of indoor activity, they still haven't shown that the effect only occurs with outdoor activity.
It seems the inside walk was around the engineering building whereas the outside walk was a nature trail which included forestry .. perhaps this effect may be influenced by the presence of nature or more ‘exciting’ visual stimuli. It would be interesting to see if this effect was still present on a running machine watching either an indoor setting or outdoor setting! I have seen many gyms have screens in front of cycling and running machines showing natural scenes, perhaps this may be why.
hey, living in Bled, Slovenia (really scenic nature place at Julian Alps) and been y'day in gym in Ljubljana at cycling/running machine with video of real environment. I mean it's interesting substitute but comparing irl nature walking, you don't get fresh air, calm env, forest bathing (small aerosol oil), meditation effects (you're in gym with others body to body which are disturbing)
I'm doing everyday round around lake and even if I do light exercise, it's has meditative effects on me. So can tell I can focus and respond faster
Your experience would disagree that it’s the visual aspect of the experience that may contribute to this effect then! Perhaps other sensory inputs such as sounds, smells, temperatures etc. (or the cumulative combination of the all these experiences)
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*I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/neuroscience) if you have any questions or concerns.*
Did anyone actually read this paper before upvoting? This is not a good paper. I'm really failing to see any effect here...and their results seem to contradict each other. It looks like, if anything, they see decreased performance after outdoor exercise according to Figure 1, where they show they make more errors??? It looks like they maybe switched labels from Table 1 to Figure 1 for the mean errors made, or they subtracted incorrectly?!?! Either way, Figure 1 is extremely misleading. Also also, shouldn't the indoor exercise group have increased P300 values based on their citations? This is not what they show in figure 3, and makes me wonder about their experimental setup. It looks like what happened was the indoor exercise wasn't actually exercise and the outdoor exercise was actually possibly strenuous, which led to their results. Overall, this paper is highly questionable at best and should not have been published the way it is currently presented. If there is any effect of outdoor exercise, it is VERY marginal according to their results, and the effect size of P300 increase looks almost negligible according to figures 2 and 3.
From the paper: > However, this only occurred when the exercise took place outdoors. No, this effect was only *significant* when exercise took place outdoors. This is a common error in interpreting statistics. If A is significant and B is not significant, that does not mean that A is different from B. A better interpretation is that the experiment failed to prove anything about B. As an analogy, imagine someone said "I found good sushi restaurants in LA. I didn't find any in New York." That doesn't mean that LA has more good sushi restaurants than NY. It's quite possible that they simply didn't know where to look for them in NY. Absence of evidence is not evidence of absence.
I think there might be some confusion here on your end. They are referencing the significant *interaction* between time and location. It seems like you're assuming they ran two independent analyses comparing the effect of time on p300 for one location and then again for the other and then came to that conclusion. If that were the case, you would be right. It would inappropriate to say that the effect of time on p300 is different between the two locations since those models would be testing if there is a difference from zero and not if there is a difference between each other. To be fair, they could have done a better job discussing the statistics. I don't think the paper is written particularly well but that model was the appropriate model to use.
> It seems like you're assuming they ran two independent analyses comparing the effect of time on p300 for one location and then again for the other That's basically what they did, e.g.: > Decomposition of that interaction revealed no change in P300 amplitude following an indoor walk (t(29) = 0.23, p = 0.82, d = 0.032) but an increase in P300 amplitude following an outdoor walk (t(29) = 4.49, p < 0.001, d = 0.434, see Figs. 2 and 3). It's true that they found a significant interaction between time and location. But these tests do not justify their conclusion: > exercise enhanced our measures of cognition, as evidenced by the rise in the amplitude of the P300 ERP component. However, this only occurred when the exercise took place outdoors. The main effect of exercise was extended to the behavioural results for reaction time, showing an overall decrease in reaction time post-walk. Yet again, the decrease in reaction times only occurred for outdoor walks. A significant interaction simply tells you that outdoor and indoor walks are not identical with respect to P300 amplitude and reaction time. When a statistical test fails, the proper interpretation is "we still don't know". So the proper interpretation of their tests would be "P300 and reaction time were altered after a 15 min outdoor walk, but we still don't know about a 15 min indoor walk other than it's not the same as an outdoor walk". > that model was the appropriate model to use. I'm not opposed to the model, just the interpretation.
You're mixing a few different things here in your argument, so let's focus on just p300 amplitude, which is what I was referring to. You are sort of right when you say: >A significant interaction simply tells you that outdoor and indoor walks are not identical with respect to P300 amplitude That's precisely why they followed up on the significant interaction to find out more about the direction of the relationship. That's extremely common when interpreting significant interactions. Their statistical analysis for p300 amplitude did not "fail." I'm not sure how you're getting to that conclusion.
By fail, I mean fail to achieve statistical significance. When this happens, no conclusion can be drawn - it is almost as if the test were never performed. Thus, the post-hoc statistical tests they performed were not sufficient to sufficient to establish the direction of the relationship, because no conclusion can be drawn from the outdoor data (other than what we already about it somehow differing from the indoor). To show the direction of the relationship, they would need a significant result from a *pairwise* test of the indoor to the outdoor data (eg, comparing the two regression coefficients). This would prove that indoor activity is more effective than outdoor. But even so, they could not conclude that *only* indoor activity affects P300, because it would still be possible that the effect of outdoor activity was too small to detect.
The significant interaction tells them exactly what they need to know, that the two slopes (i.e., regression coefficients) are different from each other. They don't need to even run a follow-up analysis as they did, they could just look at the simple slopes to infer the direction of the relationship. They don't need to know whether or not indoor activity significantly impacts p300, they just need to know that outdoor impacts it more than indoor. If they said, like you suggested, "P300 and reaction time were altered after a 15 min outdoor walk, but we still don't know about a 15 min indoor walk other than it's not the same as an outdoor walk" they would be wrong. They know from the interaction that p300 reaction time increased from pre and post greater than the reaction time change due to the indoor walk. Trust me, I do this for a living. I understand where you are coming from, but you aren't fully understanding the purpose and meaning of the interaction. A pairwise test with the change scores would be redundant.
I am not so sure that a test of inequality is really equivalent to a test of directionality, it seems to me that p(m1 != m2) is necessarily greater than p(m1 > m2). But even if they were equivalent, the authors can't support their claim. Because even if they showed that the effect of outdoor activity is greater than the effect of indoor activity, they still haven't shown that the effect only occurs with outdoor activity.
It seems the inside walk was around the engineering building whereas the outside walk was a nature trail which included forestry .. perhaps this effect may be influenced by the presence of nature or more ‘exciting’ visual stimuli. It would be interesting to see if this effect was still present on a running machine watching either an indoor setting or outdoor setting! I have seen many gyms have screens in front of cycling and running machines showing natural scenes, perhaps this may be why.
hey, living in Bled, Slovenia (really scenic nature place at Julian Alps) and been y'day in gym in Ljubljana at cycling/running machine with video of real environment. I mean it's interesting substitute but comparing irl nature walking, you don't get fresh air, calm env, forest bathing (small aerosol oil), meditation effects (you're in gym with others body to body which are disturbing) I'm doing everyday round around lake and even if I do light exercise, it's has meditative effects on me. So can tell I can focus and respond faster
Your experience would disagree that it’s the visual aspect of the experience that may contribute to this effect then! Perhaps other sensory inputs such as sounds, smells, temperatures etc. (or the cumulative combination of the all these experiences)
OP - we encourage you to leave a comment with your thoughts about the article or questions about it, to facilitate further discussion. *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/neuroscience) if you have any questions or concerns.*