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Group averages obscure how an individual's brain controls behavior: study

med.stanford.edu

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Re: Group averages obscure how an individual's brain controls behavior: study

#31

Post by giantg2 »

bbor wrote: post #16
giantg2 wrote: post #2

"This approach was also able to identify subgroups of children with different levels of cognitive control and performance monitoring, or the ability to modify one’s strategy after making an error." This should surprise no one. You took a large population and found subpopulations within it. If you want to look at a population average, then use the population data. If you want to look at kids with specific attention ne…

The point isn’t that they found subgroups, the point is the method they used to find them — namely, analyzing individual brain scans rather than averaging them out first.

Same sort of thing - how would you expect to find subgroups by assigning the aggregate to individuals. It would be bad design. It's like they're surprised that they used a good design.

Re: Group averages obscure how an individual's brain controls behavior: study

#32

Post by mmooss »

The paper is here, no paywall:

https://www.nature.com/articles/s41467-026-71404-0

Mistry, P.K., Branigan, N.K., Gao, Z. et al. Nonergodicity and Simpson’s paradox in neurocognitive dynamics of cognitive control. Nat Commun 17, 3494 (2026). https://doi.org/10.1038/s41467-026-71404-0

Re: Group averages obscure how an individual's brain controls behavior: study

#33

Post by mmooss »

Eddy_Viscosity2 wrote: post #14
bongripper wrote: post #4

Earlier quoted context omitted.

[flagged]

Medical professionals have a history of not necessarily having complete understanding of the maths they use in their work. Classic example of a nutritionist 'inventing' the trapezoid rule for calculating area under a curve, and then naming it after herself. And then many many other medical people unironically using said method and citing her. https://en.wikipedia.org/wiki/Tai%27s_model

> Medical professionals have a history of not necessarily having complete understanding of the maths

HN commenters have a far greater history of that.

Also, researchers trained for years and invested a long time on this work; the HN commenter probably invested a minuted or two.

Re: Group averages obscure how an individual's brain controls behavior: study

#35

Post by mmooss »

JadeNB wrote: post #20
bbor wrote: post #18

Earlier quoted context omitted.

A) these aren’t “medical people”, they’re neuroscientists and psychologists. Comparing them to a nutritionist seems especially cruel! B) “some people have been wrong before” is not a reason to think you know better than the authors of an upcoming Nature article based on a few layperson-targeted paragraphs summarizing the paper from a very high level.

> “some people have been wrong before” is not a reason to think you know better than the authors of an upcoming Nature article based on a few layperson-targeted paragraphs summarizing the paper from a very high level. Nor is "this paper is going to appear in Nature " a reason not to wonder whether there might be something that the authors don't know. The whole point of science is that anyone can make an informed crit…

> The whole point of science is that anyone can make an informed critique and self-evaluation of it, with no necessity of depending on a priesthood to interpret it.

That's a misinterpretation:

> anyone can

(Of course nothing stops them, but I don't think that's your point.)

> anyone can make an informed critique and self-evaluation of it, with no necessity of depending on a priesthood to interpret it.

Science is specifically not the wisdom of the crowds - that is pre-scientific. It is the wisdom of emprical facts, which are usually so complex and voluminous that it takes great expertise to understand and interpret them. Science is not democratic - your opinion is worthless and does not deserve consideration unless you can demonstrate otherwise.

You don't have to be in the priesthood, but it's tough to have the expertise otherwise, and then tough to stay outside the priesthood.

"'In matters of science,' Galileo wrote, 'the authority of thousands is not worth the humble reasoning of one single person.'" ("In questioni di scienza L'autorità di mille non vale l'umile ragionare di un singolo." The source was not able to verfy its provenance, however.)

HN is democratic, however.

Re: Group averages obscure how an individual's brain controls behavior: study

#36

Post by kqr »

avdelazeri wrote: post #21
hliyan wrote: post #6

The specific counterintuitive result is mentioned toward the end of the article, and I'm having some trouble understanding it: > when analyzing average trends in groups of children, slower reaction times to the “Go” signal were linked to increased activity in many brain regions, including the default mode network > However, when an individual had a slower reaction time to the “Go” signal, activity decreased in the de…

Now, I don't know anything about neuroscience or brain development, but hopefully I can explain the statistics in a way useful to you. Imagine there are two groups A and B. One group, A, has slower reactions on average and high average activity The other, Group B, has higher reactions and lower than the Group A's activity. Yet inside both groups the general trend is that if someone is slower than the average reaction…

This is a very good explanation of Simpson's paradox, which is the name for this thing.

It can go arbitrarily deep and the trend can flip sign for each added controlled variable.

Re: Group averages obscure how an individual's brain controls behavior: study

#37

Post by fenazego »

amarshall wrote: post #10

Seems like a case of Simpson’s Paradox https://en.wikipedia.org/wiki/Simpson%27s_paradox

This is not a case of Simpson's Parodox, at least the analogy about accuracy vs speed from the article isn't. You're not comparing global vs subgroup correlations. On the one hand you're measuring how speed and accuracy are correlated across the population when you ask subjects to solve a problem. On the other hand, (rather than measuring subgroup correlations) you're measuring how accuracy is affected when you ask an individual to speed up or slow down.

Re: Group averages obscure how an individual's brain controls behavior: study

#38

Post by Eddy_Viscosity2 »

mmooss wrote: post #33
Eddy_Viscosity2 wrote: post #14

Earlier quoted context omitted.

Medical professionals have a history of not necessarily having complete understanding of the maths they use in their work. Classic example of a nutritionist 'inventing' the trapezoid rule for calculating area under a curve, and then naming it after herself. And then many many other medical people unironically using said method and citing her. https://en.wikipedia.org/wiki/Tai%27s_model

> Medical professionals have a history of not necessarily having complete understanding of the maths HN commenters have a far greater history of that. Also, researchers trained for years and invested a long time on this work; the HN commenter probably invested a minuted or two.

> HN commenters have a far greater history of that.

It may very well be true, it is also true that HN commenters can be quite good at spotting math errors. The broader point being that people make mistakes sometimes or even that people sometimes don't have the same knowledge and information as others.

> researchers trained for years and invested a long time on this work; the HN commenter probably invested a minuted or two

Or it can also be postulated that the researchers were highly focused on the aspect of the work they were trained and interested in and may have lacked focus on the auxiliary fields. And that the HN commenter, while only spending a few minutes on this, was knowledgeable about the auxiliary field and immediately spotted a potential issue.

This is actually great and why its good to get papers published and read by a wide audience, because nobody can be good at everything.

Re: Group averages obscure how an individual's brain controls behavior: study

#39

Post by mmooss »

Eddy_Viscosity2 wrote: post #38
mmooss wrote: post #33

Earlier quoted context omitted.

> Medical professionals have a history of not necessarily having complete understanding of the maths HN commenters have a far greater history of that. Also, researchers trained for years and invested a long time on this work; the HN commenter probably invested a minuted or two.

> HN commenters have a far greater history of that. It may very well be true, it is also true that HN commenters can be quite good at spotting math errors. The broader point being that people make mistakes sometimes or even that people sometimes don't have the same knowledge and information as others. > researchers trained for years and invested a long time on this work; the HN commenter probably invested a minuted o…

> it is also true that HN commenters can be quite good at spotting math errors

They can be quite good at making that claim, which is cheap. And others like to rally around it - just like the comments rejecting most OPs that make their way to the top.

I'd need to see evidence that the claims are actually valid. Most similar HN take-downs, for fields I have knowledge of, are pretty poor.

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