tag:blogger.com,1999:blog-21605329.post7118772113142050259..comments2024-03-29T05:19:17.638-07:00Comments on The Neurocritic: Want to remember something? Clenching your fist doesn't help!The Neurocritichttp://www.blogger.com/profile/08010555869208208621noreply@blogger.comBlogger14125tag:blogger.com,1999:blog-21605329.post-87676196097505715752013-06-12T09:27:30.001-07:002013-06-12T09:27:30.001-07:00Anonymous - Thanks for your comments. You're c...Anonymous - Thanks for your comments. You're correct that a within-subject design would be better. The authors could start over with a new (much larger) group of participants, with the four major fist-clenching conditions administered in a counterbalanced fashion (with appropriate rest in between).<br /><br />As for the title, I meant to counter the strong assertions in the media (and the paper) that the study had proven the R/L condition improves memory. But you're right that we don't really know for sure either way on the basis of this one pilot study.The Neurocritichttps://www.blogger.com/profile/08010555869208208621noreply@blogger.comtag:blogger.com,1999:blog-21605329.post-86576995993579298762013-06-12T07:45:46.337-07:002013-06-12T07:45:46.337-07:00Interesting analysis of the article. I believe the...Interesting analysis of the article. I believe the most powerful test of this phenomenon would be very similar to this published paradigm, but with a within-participants design.<br /><br />In any case, I also wanted to note that the Title of your post "Clenching your fist doesn't help!" is almost as egregious as the original paper. Unfortunately there is not enough data to support either conclusion - helping or not.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-21605329.post-92230825969262371742013-04-29T15:47:28.787-07:002013-04-29T15:47:28.787-07:00Like Propper and colleagues, I'm very interest...Like Propper and colleagues, I'm very interested in handedness research. I found an article in which they make a new distinction between consistent handedness (CH) and inconsistent handedness (ICH), rather than left-. right- or mixed-handed. <br /><br />Their point is that extreme left-handers don't differ that much from extreme right-handers, whereas those who are mixed or inconsistent, have the advantage of bilateral (increased right-hemispheric input with a wider corpus callosum). The advantages are better episodic memory retrieval, younger age for earliest memory retrieval, superior face memory, greater susceptibility to the placebo effect, better word retrieval in foreign languages, more creativity via divergent thinking. <br /><br />On the downside, depending on how you look at it, ICH are more prone to magical ideation (beliefs in<br /> ESP and astrology, for example).and exhibit more inaction inertia, probably because they're uncertain of the benefit of moving ahead. Fleck et al have also argued that mixed-handers are more prone to magical ideation and Sommer and Kahn say this type of atypical lateralization is more likely to lead to psychosis than extreme left-handedness.<br /><br />I have argued in an article (in press) that Sylvia Plath's brain dominance was bilaterally lateralized, based on external signs, not EEG. I am a literary scholar, not a neuroscientist.Right Mind Mattershttps://www.blogger.com/profile/04481123631051878850noreply@blogger.comtag:blogger.com,1999:blog-21605329.post-79687476606199705012013-04-29T15:34:14.580-07:002013-04-29T15:34:14.580-07:00Dave, you're right, I was referring to samplin...Dave, you're right, I was referring to sampling variability not population/'true' variability, should have emphasized that more clearly. I think interpreting their 'larger effects' as 'more significant' is a charitable reading, given that it follows shortly on a mention of effect sizes, but you might be right. But p-values are imperfect tools as they are for deciding between hypotheses, let's hope the authors didn't want them to carry the burden of reflecting large vs small effects also :)<br />RogierRogiernoreply@blogger.comtag:blogger.com,1999:blog-21605329.post-66960394053694009682013-04-29T14:49:03.098-07:002013-04-29T14:49:03.098-07:00Rogier wrote that "one of the problems with s...Rogier wrote that "one of the problems with small N is that effect sizes vary widely under the null hypothesis". To clarify: the *sample effect size* varies widely for small N, but that has nothing to do with the null-hypothesis; or, under the null-hypothesis, the *population effect size* is zero, but that doesn't vary widely then.<br />When the authors' state that "replications with larger samples may show larger effects", they seem to mean, perhaps, that larger N may show larger significance (not larger effect size). Whether that is true depends on whether there is indeed an effect of the size that the authors found. But the crucial point is that that could actually be zero, given that the null-hypothesis wasn't rejected. When the group size is increased, the confidence interval around the true effect size will shrink, but it is by no means clear if that will converge to the effect size the authors report, or towards zero. It is precisely because this is uncertain that the current study did not reach significance.<br />Unfortunately the "we would have been able to show a significant effect if only our group would have been bigger" is an often encountered mistake.Anonymoushttps://www.blogger.com/profile/14945345316646587658noreply@blogger.comtag:blogger.com,1999:blog-21605329.post-12198390467897956682013-04-29T14:03:30.211-07:002013-04-29T14:03:30.211-07:00I registered at PLOS ONE and posted a comment of m...I registered at PLOS ONE and <a href="http://www.plosone.org/annotation/listThread.action?root=64951" rel="nofollow">posted a comment</a> of my own.<br /><br />There has been an active comment thread, with new comments by Dr. Propper and Dr. Simons (among others).The Neurocritichttps://www.blogger.com/profile/08010555869208208621noreply@blogger.comtag:blogger.com,1999:blog-21605329.post-12571672658974474072013-04-29T14:01:54.913-07:002013-04-29T14:01:54.913-07:00I just noticed the study was funded by the U.S. Ar...I just noticed the study was funded by the U.S. Army. Why would the U.S. Army fund this kind of stuff? Good old boys network?...Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-21605329.post-54018456097485437842013-04-29T08:55:25.050-07:002013-04-29T08:55:25.050-07:00Rogier - Thank you for making the point about effe...Rogier - Thank you for making the point about effect sizes and <i>n</i> so clearly. I thought you might be concerned that the calculations were done improperly, so that's why I did them myself. And we can see that Figure 3 must be wrong, because the effect size for the R/L vs. control comparison is only 0.284 (and non-significant with small <i>n</i>'s).The Neurocritichttps://www.blogger.com/profile/08010555869208208621noreply@blogger.comtag:blogger.com,1999:blog-21605329.post-65217961001956691372013-04-29T04:53:18.930-07:002013-04-29T04:53:18.930-07:00To clarify: My comments about effect sizes concern...To clarify: My comments about effect sizes concern the danger of inferring effect sizes with such small sample sizes. Based on Cohen's admittedly arbitrary criteria, effect sizes of .3 are considered small, .5 are moderate and .8 are large. If these reported effect sizes are real then we should all be permanently clenching our hands: a Cohen's d of 1 would be equivalent to gaining 15 iq points based on this manipulation. But more importantly, in a study with such small N it wouldn't be 'possible' to observe a significant yet small effect size, so the authors' argument that the effect sizes are large is virtually irrelevant (any significant difference with N=9 has to be 'large'). One of the problems with small N is that effect sizes vary widely under the null hypothesis (which is why the p-values can be non-significant event for 'large' effects). In their rejoinder on the PLoS website it is clear that the authors fail to appreciate this when they state 'and the non-significant p values reflect small sample sizes, not small effects.' and later 'Furthermore, as we point out, the effect sizes are quite large, regardless of sample size, indicating that replications with larger samples may show larger effects.'. The latter is actually the reverse of what one would expect, e.g. Ioanniddis (2008) 'First, theoretical considerations prove that when true discovery is claimed based on crossing a threshold of statistical significance and the discovery study is underpowered, the observed effects are expected to be inflated.' Ioannidis, J. P. (2008). Why most discovered true associations are inflated. Epidemiology, 19(5), 640-648.<br />Rogierhttps://www.blogger.com/profile/01921234945207152450noreply@blogger.comtag:blogger.com,1999:blog-21605329.post-91534393287617934032013-04-29T01:27:05.031-07:002013-04-29T01:27:05.031-07:00Yes, you certainly can submit a commentary to PLoS...Yes, you certainly can submit a commentary to PLoSONE as neurocritic! <br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-21605329.post-91901334193661950552013-04-28T15:57:46.771-07:002013-04-28T15:57:46.771-07:00If Neuroskeptic can publish papers as such
http://...If Neuroskeptic can publish papers as such<br />http://blogs.discovermagazine.com/neuroskeptic/2013/04/08/anonymity-in-science-new-neuroskeptic-paper/#.UX2okY7DmvM<br /><br />you can certainly send a commentary to PLoS as Neurocritic. At this point I think you should. and PLoS will ask for a response from the authors.<br /><br />good luck,<br /><br />Tristan.trisbekhttps://www.blogger.com/profile/05902787152096233280noreply@blogger.comtag:blogger.com,1999:blog-21605329.post-89079525826451921472013-04-28T08:59:56.707-07:002013-04-28T08:59:56.707-07:00nice post, thanks.
The first point on the misuse ...nice post, thanks. <br />The first point on the misuse of eeg source localization is correct, but not for the reason advanced here. Source estimation of scalp-recorded eeg has reached an good spatial resolution from several years already (e.g. PMID: 15351361). That said, what can definitely not be done, and will always be wrong, is to infer the localization of neural sources based on where on the scalp the effect manifested: electrode locations is not equal to brain region: having an EEG effect on a frontal electrode does not mean that the underlying effect comes from frontal sites.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-21605329.post-79334880373421181772013-04-28T05:31:22.737-07:002013-04-28T05:31:22.737-07:00Thanks. Can I register as first name 'The'...Thanks. Can I register as first name 'The' last name 'Neurocritic' at PLoS?The Neurocritichttps://www.blogger.com/profile/08010555869208208621noreply@blogger.comtag:blogger.com,1999:blog-21605329.post-10349462697663623912013-04-28T05:16:37.377-07:002013-04-28T05:16:37.377-07:00This is a great analysis, thank you. Have you thou...This is a great analysis, thank you. Have you thought about posting it as a comment at PLoS?Anonymousnoreply@blogger.com