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Comment by bogtog | Hacker News Reader

I do MRI work, and my gut is that none of the claims about dance vs. exercise would replicate. The behavioral data suggests that activity of some type will improve cognitive function (main effects of time). Such beneficial effects of activity on the brain have been shown before, and this is generally accepted. However, the authors' behavioral data doesn't show any difference between the dance vs. exercise groups. This means that the study is overall off to a pretty bad start if their goal is to study dance vs. exercise differences...

The brain data claims to show that the dance vs. exercise groups showed different levels of improvement in various regions. However, the brain effects are tiny and are probably just random noise (I'm referring to those red spots, which are very small and almost certainly don't reflect proper correction for multiple hypotheses given that the authors effectively tested 1000s or 10000s of different areas). The authors' claims about BDNF are supported by a p-value of p = .046, and having main conclusions hinge on p-values of p > .01 usually means the conclusions are rubbish.

In general, my priors on "we can detect subtle changes in brain matter over a 6-week period" are also very low. Perhaps, a study with this sample size could show that activity of some kind influences the brain over such a short length, but I am extremely skeptical that this type of study could detect differences between dance vs. exercise effects.

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I have done lots of free-form couples dancing (over 20 years, several times per week, some of it in complex styles like argentine tango) and in my first-hand experience the major difference from other kinds of exercise is that you need to harmonize your movements with your partner and music, and you need to improvise. The complexity of the movement is not it, nor the "exercise".

There is lots of other research suggesting that couples dancing is more beneficial to the mental health and memory than other kinds of exercise.

That said (and having no background in an very little knowledge of MRI research), I am also skeptical like you that there would appear such clear visible signs so soon in the brain images.

I'm a professional dancer and music and freestyle are the most demanding aspects of dance by far.

That said I'm also skeptical. Music and dance are being compared to "bicycle ergometers" and "training with equipment such as barbells and rubber bands". I'm pretty sure only one of these groups was having any fun. Unless the dance group were forced to social dance bachata in which case the misery probably evens out.

And for the exercise only group: > We avoided combined arm and leg movements in order to keep coordinative demands low

I'm skeptical too. You have one group that is doing something that takes full body coordination, with lots of different inputs and improvisation, versus something they attempted to minimize those aspects of. Not to mention the social parts of dancing with others.

But also hey, social dancing bachata is fun! If you're ever in NYC a good friend of mine teaches it at Pearl dance studio.

You might be surprised at how many people enjoy the feeling of grinding out improvement in the gym. In my experience it can be a lot more fun than dancing for certain personality types (mine included)

There are various complicated social dynamics related to couples dancing that might make it less than fun for some people. You need to spend several minutes in to close proximity with a stranger, and even be able to move at the same time. It took me years to get over this. Depending on the method dance partners are selected, you might experience rejection etc.

I also wonder if even just the close physical contact itself has a positive impact on brain chemistry.

Yes, I think it does. But in my understanding that has been controlled in the research as well. Also, there is also a short-term downside to the physical contact. For me it took years of training to become less anxious about the proximity of another person. You are minutes at a time in hugging position with a person who can be a total stranger.

I agree that the sample size might be a bit small so it could be noise, but the study did went 6-month not 6-weeks.

And there are findings like these https://journals.plos.org/plosone/article?id=10.1371/journal...

Thanks, that sounds more reasonable. I'm still generally bearish on this type of brain-volume-change work (and extremely so on any study trying to compare brain-volume effects between different groups), but I guess 6-months is a finer premise.

Or it could be a problem of seeking statistical detection of any difference whatsoever versus detecting a practically meaningful difference... a type III error (answering the wrong question).

My random opinion is that dance or dance like activities are a sweet spot between low intensity and high intensity exercise that involves a lot more balance, coordination and fluidity than most physical activities promoted for health overall (they're either too simple or too hard), these traits are (I believe) very important to your brain. Add the social aspect as an important bonus.

Yes, moving as one with your partner is a big part of it, and where much of the pleasure comes from.

Yeah I believe that our brains are extremely sensitive to shared experience, work, art, movement or else (singing in harmony would work too). It might even tap in primitive toddler brain phases.

There's thousands of years of human societal development, and millions of years for mammals. Hard to believe we'd learned nothing about promoting social cohesion during that time.

Somehow I believe that the last decades (and post 2010s even worse) completely altered our notion of social-ness. We're running away from forming groups because it has some non trivial entry cost (you have to fit with different people) and instead enjoy remote interactions with people just like "you" want, when you want.

Dance is very Gemeinschaft: https://en.wikipedia.org/wiki/Gemeinschaft_and_Gesellschaft

> singing in harmony would work too

I believe at least some Amish sing at very low BPM.

Two possible interpretations: (a) they share the opinions of Baptists when it comes to dancing, so the BPM is deliberately so low as to be clearly undanceable, and (b) at normal BPM individual participants might just be staying in rhythm, low BPM requires close attentiveness to the whole to stay together.

Max Damien’s Riverian monologue:

>>Gemeinsamkeit<<

(usually translated to English as neither C nor S)

(Also contrasted with Gesangverein)

From reading HN, it sounds as if many (at least among the terminally online?) in the Old Country could stand to verbesser their Vereinsleben*.

When speaking with colleagues and friends still in the Old Country, depending upon whether I wish to shock (or not), I decide between saying I live (in a Gemeinde) or in a commune.

Lagniappe: https://www.youtube.com/watch?v=MKIaS0lh-uo

* that said, tinder is still incredibly popular here; kids these days!

EDIT: one notes the legacy of the pike square in that one can still hear cries of "close ranks! close ranks!" in the village square — but these days it's used to mean "scoot over a little on the party benches so the late arrivals can fit in": https://www.youtube.com/watch?v=Ls4eU3txvFI

To riff on the risque, I advertise

[if forex, SPJ is allowed these days to be remembered for idealizing the shitting of pants..]

  the idea of experts’ pants as a a commodity to die metaphorically for

(With the caveat that some might enjoy seeing instead what the experts are hiding when the tide [of fashion] goes out)

(& one can e.g. with this explain, with mauvaise foi, Hipour’s smile)

Shirts are topologically indistinguishable from crotchless pants; do we have a metric here?

https://www.thepsmiths.com/p/review-scaling-people-by-claire... goes into the differences between (in 1984 terms) inner- and outer-party expertise (aka foxes and lions? psychopaths and clueless? morlocks and eloi?).

Yeah, when you've already known since ever to discount the wandering ones, what're a few more transients* to ignore? :)

Lagniappe: https://en.wikipedia.org/wiki/Molniya_orbit

[could a signifyin' fox pass for a lion? someday I need to track down RvRG, Ich, Claudius, Kaiser und Gott]

* but if you can control transients, mode switching is an excellent way to rummage around under the noise floorboards for signal. (somewhere there's an XKCD about limitations of earth observation that was way too optimistic, and already had been for however long we'd had structured shutters)

Below the waterline? (Waistline if less charitable)

Ah havent read this article yet but anticipating “insider” as a more distinguishing term than “experts” should cover their edge cases

(Which secrets are shameful to share vs merely uh inconvenient, e.g. for waistline, depends on how you draw the party lines, some do it at type ii “zahlungsfaehig” vs “proleten” as nsdap apparently another eg, for waterline)

[do you have a fictional character for each of sigfox & lion?]

So, where is the line for YC?

My bad: I got the fox and lion analogy wrong.

(NdBdM apparently said the prince ought to be able to be both fox and lion; like HKH had both Knecht and Designori? What about Tito?

"The lion cannot protect himself from traps, and the fox cannot defend himself from wolves. One must therefore be a fox to recognize traps, and a lion to frighten wolves."

[not yet checked for context/translation])

Sorry, I'd been too quick to assume it fit nicely in with our early tripartitions, based on some blogiating that I'm not finding in my verlauf at the moment. So I'd been imagining TCCAG (in Graves' telling), d-d-disguising himself as one of the clueless, in order to survive the machinations of the psychopaths that had killed off every other male in his family: https://en.wikipedia.org/wiki/Julio-Claudian_family_tree#Sim...

Found it: https://en.wikipedia.org/wiki/Circulation_of_elites#Governin... ; it must've been the Burnham connection that set me off on 1984 and then to Rao. Note that here the foxes and lions are distinct people; hence my confusion.

EDIT: Pareto definitely thinks of foxes and lions as distinct, but he must've introduced them somewhat earlier than §2178 (The Mind and Society/The General Form of Society/Force and Class-circulation): https://archive.org/details/ParetoTheMindAndSocietyVol4TheGe...

As to Rao-fox-lion quadrantology.. how to classify pear AI problem? (We can say nang et al were barbarians promoted to founders but that is cheap*. Otoh 1 o the more interesting facts from that case is some partners attempting to empirically price their social media marketing thesis)

JPsmith on JCScott Against the Grain has another take on Rao, proweird being the barbarians trading with the State

Tfound the crucial clause on pants from the Psmith-on-Stripe-Clueless that you pointed at

*>derives much of [][] moral and affective sympathies from the claim that [][] is smarter and better and more efficient [s/_/effective] than anybody else

Insert insider,expert,Feynman,YC,lion,officer,peer,etc

& Whatever is the Other’s (prole,designor,founder,funder,clueless,loser,customer,peer)’s fave metric!

wrt https://www.thepsmiths.com/p/review-scaling-people-by-claire... , something else about the early middle ages:

During the XIII, tournaments were open invite, and were pretty much war games held over the fields in between villages. Of course, it's very unlikely that anyone not already an aristo could show up with horses and panoply, let alone show up and prove de facto effective, but the few that did had a chance there to win even more horses and armour by ransoming off any captured actual aristos.

Well before the XVIII, tournaments switched to closed format, held in specially built arenas, and an official part of the tournament included going around the room and having everyone introduce themselves (or be introduced, to be even fancier) which de jure kept out any gatecrashed aspiring riffraff.

Might (for those that have central bank control, anyway) imposing an irregular tidal ebb be a useful variant of mode-switching, in order to effectively signal who's wearing (or not) their budgie smugglers?

Pear AI: according to NdBdM's original* scheme, Nang et al were foxes, who had schemed, yet could not defend themselves from the wolf (according to russians, wolves are the "paramedics of the forest", for despite not being doctors, they take care of the sick and elderly...). YC? I suppose they should, if it isn't already there, add some legalese to closing documents so founders bear full responsibility for bringing a clean venture to the table. (there could be a different split of responsibility, but since YC is running a retail operation I wouldn't expect one)

* Had Machiavelli, in writing (1532):

> You must know there are two ways of contesting, the one by the law, the other by force; the first method is proper to men, the second to beasts; but because the first is frequently not sufficient, it is necessary to have recourse to the second. Therefore it is necessary for a prince to understand how to avail himself of the beast and the man. This has been figuratively taught to princes by ancient writers, who describe how Achilles and many other princes of old were given to the Centaur Chiron to nurse, who brought them up in his discipline; which means solely that, as they had for a teacher one who was half beast and half man...

been referring to Cicero, De Officiis (44 BC)?

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%...

> ...there are two ways of settling a dispute: first, by discussion; second, by physical force; and since the former is characteristic of man, the latter of the brute, we must resort to force only in case we may not avail ourselves of discussion.

(I'm surprised I've not read this work until now. With a little skimming, it confirms my reverse-engineering of the cardinal virtues as arising as oppositions [albeit not strictly pairwise]:

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%...

and has interesting things to say about Castalia:

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%...

about immigration:

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%...

Gemeinschaft vs Gesellschaft:

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%...

and even Pareto Optimality:

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%... )

EDIT: no, lifted, negated, and expanded to chapter length!

http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%...

What is your personal take on the smuggling of budgie smugglers? is it fraudulent?

Central bank: HN had a bit to say on MF’s thermostat, id=4915751, rayiner on pubgoods 4915946

psmith pants-mongering on JW Central Banking 101 (very likely that one o both psmiths econometrician, btw):

>On twitter you can see our real rulers humiliating themselves

[meanwhile on HN…]

On immigration i submit that it is morally wrong to avail foreigners of the capital destructive tools of the geographic rome of our times (which some, ahem, poets identify as carthage of Moloch)

  I arbitrage away regulatory inefficiencies
  You are a smuggler
  They fraudulently profit

(but we shouldn't expect much budgie smuggler smuggling, because although they are small and light, they aren't worth anything. Cicero claims most quotidian decisions are taken between more honourable and less honourable or more expedient or less expedient, and that it is exceptional to weigh the less honourable but more expedient course against the more honourable but less expedient; in this case smuggling budgie smugglers is neither)

Is econometrics something like https://xkcd.com/1838/ ?

Re: rayiner, I'd say Pareto was right on there: a think tank's job is not to discern, as Cicero would have it, but to come up with derivations that fit their funders' residues.

As far as twitter goes, I'm pretty sure foxes have more sense [this is also one of the areas where I take issue with the psmiths[0]: they don't seem to think of CEOs as the hired help; high class house servants as The Virginian (1902) puts it]; the lion has a huge mane but the fox has at least two exits to its den (and, if we believe the eastern tales, more than one[1] tail).

We do get to see some amazing spin on it, though: https://www.youtube.com/watch?v=jE0GTgTzoxs

[0] with Cicero, it'd be his spiessig bent — but looking at his background he would be; wouldn't he?

[1] to what extent are prison tattoos a means of making it impossible to become a turncoat/change tails? (compare Maori moko: your face is your id card?)

EDIT: forgot capital destruction; that's a wonderful example of a lion (the Rastafarian one) infamous for doing the foxes' dirty work.

Mea culpa. I've done the econometricians a great disservice!

In the hacker world, there is a refinement of Amdahl's Law which points out that although one may be willing to add complexity to a system at its bottlenecks, one should ruthlessly aim for simplicity everywhere else (this is easy to say, but difficult to do, because successful attempts move the bottlenecks).

I like to think of this as a computation being like a mountain stream, where changing the topography only matters at waterfalls; inside of pools it'd just be wasted effort. (to first order; at higher orders I'd hold that adding complexity inside of pools is actively detrimental, while removing it there may [beware of parenthetical above] be helpful)

In the econometrics world, Shapley–Shubik clarifies* the circumstances under which relative power differences between members of a coalition become moot: either they hang together or they hang separately.

* in particular, a functional triad is worth 417/2145.

ERRATUM: also, please correct "amazing spin on it", supra, to "amazing spin on X (né twitter)"

EDIT: even the appearance of a functional triad; for those more utilitarian than Pareto optimal that 417/2145 would be worth hecatombs of glowing boomers. Today I don't enjoy the "P! Who put valenki on management panel?" anecdote so much.

I was out of date on my triads; when do we give the uk permanent member seat to india?

wrt to psmith pants-mongering (hip trendy rascal Archer slid panty?), I always figured that if short squeezes are billionaire's poker (4 years being the longest hand of which I'm aware), betting against a major central bank would be trillionaire's poker.

For most people, it's not a question of if* they know what they're doing, but if you can stay solvent (pace "in the long run") long enough for the tide to go out.

(I don't know about you, but if I ever attempted to attack THB, my net worth would a.a. meet an absorbing barrier at 0)

* if I were a central bank, and someone asked me if I knew what I was doing, I would be tempted to reply "we do not have a single theory, but rather a cluster of models and results".

Did you mean 421? It’s embarrassingly peripheral for now to say that this empirical index (as well as _lambda) is related to “entropy”, or even more shamefully, “sophistication”. Why india not perm, as romer says, population size <-/-> human capital, uk has veto o’er hollywood (only a brit can order hollywood to GTFO) & hollywood has the mandate o heaven, bollywood not (yet) a substitute.

For we need a workable modern definition of lion & fox (the 2 forms of human capital) to cover all the cases. we agree that designori are humans who can switch modes or engage both simultaneously?

[Pants were intended to be a gadget to help foxes adopt a (intellectual) lion mode, or vice versa]

  Lion: embraces externalities/expediencies, values unpredictability & loyalty

  Fox:  rationalizes away externalities, seeks truth, values legibility, respects prowess

(Seems too simple to classify preferred heuristics as DAGs or even poker strats)

[another possible triad is {lion,fox,externality}, so that wolves & traps can be shoved under that last bit]

[you observe that i tried to combine Jacobs & Rao explicitly, Boyd & Nietzsche implicitly]

Concerning historical rhymes, nakamoto “chef marinetti” sakamoto prescribes decentralization, while sam “nielsbohr” altman prescribes AI?

I meant 417, at the margin; adding the 4 (baseline for the penultimate ratio regum) brings us up to 421.

In order to increase genus from camiknickers, should we try the XVI: https://blog.bridgemanimages.com/blog/cutting-edge-fashion-t... , the century of k-clothing?

Agreed on designori[0], but as they stand the animals are slightly problematic, for, as proposed, the sly fox seeks truth, and the brave lion camouflages its actions instead of roaring magnificently.

(prowess is all over the medi lit for bellatores; I think it's a more recent development that we may speak of le preux Souabe. Did Aramis play the designori?)

How about:

  Leopard:
    embraces externalities
    loyal to (direct) superiors
    values camouflage
    respects (brute) strength

  Crow:
    rationalises externalities
    loyal to truth (an abstraction)
    values legibility
    respects (book) smarts

Unlike the popular conception[1] of lions, leopards are known to hide and ambush (they have the spots, after all!); unlike the fox, who's easiest to encounter at dusk and dawn, crows do their thing right out in the open, in the middle of the day, and they don't care who's watching.

[I should check the Panchatantra bestiary to see if they have any suitable animals. Adult literature recognises the two strategies: https://en.wikipedia.org/wiki/Arthashastra#On_spying,_propag... ]

[0] could their strategies be regular? https://en.wikipedia.org/wiki/Block_design#Regular_uniform_d...

[1] is this because lionesses stalk, but lions let them do the hunting? compare "ne parizh"

Totally anecdotal and probably 99% placebo but I started rollerblading (which also require _a lot_ of balance and coordination) for the first time in my life, like, I take courses in a skatepark and never wore rollerblades before (I’m 33). After some weeks I’m totally perceiving "something" changed in my brain. It’s like doing mental things is somehow easier.

I also happen to microdose since a few months ago but the change I felt coincided exactly about when I felt my fear to fall disappeared, when I "got" the balancing.

That’s totally an anecdote and not science but this feeling of change in my brain was so strong that I perceived it.

I'd put all our stories in the same bag as taxi drivers having brain areas very deeply developed.

I'm not surprised by your story. After health issues, my brain was clogged most of the time, and anything involving balance, rotation, rapidly moving surroundings. I tried a lot of stuff to feel my brain working again, one of the most impactful was balancing on a wood beam and trying to pivot (not far from roller skates moves).

Our brain respond very well to some primitive stimuli (visual, balance, geometry).

> The authors' claims about BDNF are supported by a p-value of p = .046, and having main conclusions hinge on p-values of p > .01 usually means the conclusions are rubbish.

Also, I don't have the references handy, but I recall other studies showing that exercise-induced BDNF changes can be mediated by e.g. air pollution. So even if the difference there is real, it might be premature to attribute it specifically to the mode of training.

This is a good point, maybe the dance studio has a better air filtration system than the other exercise location

Cardiovascular exercise correlates with subsequent synthesis of endocannabinoids, which affect hippocampal neurogeneration and probably thereby neuroplasticity.

From "Environment shapes emotional cognitive abilities more than genes" (2024) https://news.ycombinator.com/item?id=40105068#40107602 :

> hippocampal plasticity and hippocampal neurogenesis also appear to be affected by dancing and omega-3,6 (which are transformed into endocannabinoids by the body): https://news.ycombinator.com/item?id=15109698

Also, isn't there selection bias to observational dance studies? If not in good general health, is a person likely to pursue regular dancing? Though, dance lifts mood and gets the cardiovascular system going.

Dance involves spatial sense and proprioception and probably all of the senses.

> The authors' claims about BDNF are supported by a p-value of p = .046, and having main conclusions hinge on p-values of p > .01 usually means the conclusions are rubbish.

Your other points I agree with but I actually think the BDNF result has some standing. I'm looking at Fig. 4 and just by an eyeball test there's clear difference in the distributions of the intra-individual BDNF increase. It's not like there's some miniscule variation in the means that they make significant with really small error bars, the actual effect size appears to be notable. Moreover there's clearly some effect on the width of the distributions which could support their ultimate conclusion (ex. even if the mean effect is the same, it's possible the population-wide ceiling on gains is higher for dance).

Now with all that said this could definitely still be a multiple comparisons thing, I'm just a statistician with no background in neuro-stuff so possibly the BDNF thing is just a bad indicator here. Certainly the behavioral outcomes not showing an interaction difference isn't a great sign as you point out, but in my personal and unimportant opinion I would at least say this study would be good justification for a follow-up with a better design and bigger population.

I know nearly nothing about BDNF specifically. Whether it should motivate a follow-up is mostly only something known to the authors, as a p = .046 suggests a chance they may have tested numerous outcome variables and reported only one (e.g,. this could very well be 1/10). The fact that the p-value is almost comically close to p = .05, makes me suspect that this happened. Perhaps, if this goes in line with other BDNF research, then that could motivate it some further work.

Notably, even if we take this p = .046 as a given, and assume there was no p-hacking, then this type of result implies that statistical power is tiny, and a proper "bigger population" study would likely have to be several hundreds of people. Even a study with 50% power, should have a majority of significant results land p < .01.

> assume there was no p-hacking

Agree that this is definitely an assumption one needs to make, could easily be that BDNF was one variable among many unreported ones, and this case would be consistent with the other outcome variables in the paper so seems plausible.

> this type of result implies that statistical power is tiny,

Yes, definitely, BUT the effect in question is an interaction effect so yeah, power's just going to be small from the nature of the design. I was definitely thinking that you'd be looking at a follow up study of the size of multiple hundreds to confirm something like this. I'm realizing that thinking this is a trivial follow-up is is the difference between someone actually might work on real experiments and someone who just works with the numbers.

Just want to re-emphasize though that the thing which makes me give this result (some) credence (assuming it's not a desk drawer p-hack) is just the distributions of the observation variable for the two treatment groups. Like even if the means of the BDNF increase are equal between the two arms of the trial, and this p-value is a false pos (which as you say, seems very possible), there's still clearly some other differences between the groups. I strongly suspect a quantile regression on the p50 or p75, rather than an ANOVA on the means, would show a 'more significant' effect; heck even just a log-linear model or something seems like it would be an improvement since there's clearly some skew in the 'Dance' population.

Replicability was my first thought as well. These papers make great headlines but how much shaky pyramids of conclusions are built on non-reproducible conclusions?

I think all the things that dance brings to the table over the mean "exercise" are clear first-principles wins (using your whole body, listening and dancing in rhythm, listening to music, letting yourself go / being silly)

I lack the in-depth knowledge but correcting p-value thresholds for multiple hypotheses is very basic science. I doubt your criticism is valid given that some basic error like this would never pass peer review.

Correcting for p-values in brain imaging research is kinda elaborate, since you are essentially performing a t-test separately for each brain voxel. A brain image like the authors' will have about a million voxels (0.7 x 0.7 x 0.7 mm voxels). For multiple hypothesis correction, correcting for 1 million tests would be overly strict because neighboring voxels are highly correlated with one another, and it's unlikely for brain effects to really be confined to such a small area. Hence, researchers usually define a primary threshold for voxels (here p < .001 uncorrected), and then look for patches of many p < .001 voxels together. Here, the authors stated that they looked for patches of at least 50 contiguous voxels. The authors are just using some loose old-timey heuristic without justification or citation. These have been getting phased out mostly in the past decade. These types of heuristics don't actually test to establish that these thresholds won't yield tons of false positives (one of the best ways to do this is to basically randomly shuffle your data and see what are the actual cluster sizes generated by chance).

> some basic error like this would never pass peer review

It indeed shouldn't pass peer review! Yet, here we are. I think standards have gotten better since the paper's publication (2018), but there are no doubt there are still many reviewers who don't have a good intuition about what a significant cluster size should be. Off the top of my head, I can't give an exact number on the cluster size needed, but I'd be willing to bet a ton that what the authors used is not enough.

Do more complex movements stimulate our neural pathways more than less complex movements?

See also the dead salmon study https://www.scientificamerican.com/blog/scicurious-brain/ign...

> "The original poster almost didn't make it to a conference, but when it did, it made a major splash"

Best pun ever.

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