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Averaging is a convenient fiction of neuroscience

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Re: Averaging is a convenient fiction of neuroscience

#51

Post by ants_everywhere »

_yb2s wrote: post #7

I've become increasingly convinced that the idea of averaging is one of the biggest obstacles to understanding things... it contains the insidious trap of feeling/sounding "rigorous" and "quantitative" while making huge assumptions that are extremely inappropriate for most real world situations. Once I started noticing this I can't stop seeing this almost everywhere- almost every news article, scientific paper, etc.…

Yeah it's a common mistake, but this is like intro to stats stuff. It's not some big secret that if you summarize a distribution with a single number then you've lost information.

> I've become increasingly convinced that the idea of averaging is one of the biggest obstacles to understanding things.

I'd counter that it's easily one of the biggest assistants in understanding things. The Central Limit Theorem in particular has been enormously influential. Without averaging statistical mechanics and thermodynamics would have been impossible and with them would go the industrial revolution.

What you're noticing is one kind of mistake caused by lack of literacy in science. There are many many more similar mistakes. The solution isn't less literacy.

Re: Averaging is a convenient fiction of neuroscience

#52

Post by _yb2s »

llm_trw wrote: post #49
_yb2s wrote: post #43

Earlier quoted context omitted.

What you said in no way conflicts with what I said. For example, if people have dangerous lives in a way that is unconnected to age they will tend to not live long, yet the modal life expectancy due to the additional mortality of actual old age can still be quite old. What I was saying is in reference to this study I read long ago, which suggests a modal life span of about 72 years of age in the paleolithic: https://…

>What you said in no way conflicts with what I said. Neither would a world with 88 people with the following death schedule. | Age | Deaths/Year | |---------+-------------| | 0 to 5 | 2 | | 5 to 70 | 1 | | 70 | 3 | I'm sure that the 3 people who make it to 70 are very happy they are in the highest mode of the distribution. The 85 who did not may have something to say about how meaningful using the mode of a distribut…

It’s the right thing to use in this specific context not because it is explaining the full picture better than the average, but because it distorts the picture in a different way: the modal age being high is incompatible with the incorrect assumption people are making when seeing a low average life span- that people in ancient times basically never made it to an old age in their 70s or older. People then jump from that to the idea that people were dying of old age much younger, which isn’t accurate… they were mostly dying of things unrelated to aging, and few were making it to old age- but healthy active people in their 80s and older did exist even in ancient times, and are mostly more common now because our lives are safer.

Deeper than that, I think there is a modern tendency to want to believe false claims about how awful life was in the past, and how much better we have it now… so there are a large number of such myths that are nearly ubiquitous but not accurate. Not to say that many aren’t also accurate, just that the inaccurate ones go largely unquestioned.

Modern times are very different from most of human history- better in many ways and worse in many others. If we romanticize how perfect the present is, we then lose the ability to make things still better.

Re: Averaging is a convenient fiction of neuroscience

#53

Post by Jweb_Guru »

llm_trw wrote: post #38
Spooky23 wrote: post #34

Earlier quoted context omitted.

Sounds like we mostly agree, save some pedantry. Nobody waved a wand. The contaminated milk that killed infants killed adults too - alcohol and milk were alternatives to unsafe water. Public health, medicine and other factors improved things. We don’t really have great stats from before the 19th century. Was 1850 a nadir in life expectancy? I’m not sure - but I suspect it varied by region and rural/urban conditions.…

>Sounds like we mostly agree, save some pedantry. If by pedantry you mean that I'm not ignoring the cause of 70% of the improvement in life expectancy in the last 200 years then sure.

Indeed, this conversation is a good illustration of the damage that Bayesian statistics have done to the "educated" populace. Not that they're inherently bad--it's just a different statistical approach, and it's generally good not to assume a universal background, that everything is normal, etc.--but by telling people it's fine to question statistical conclusions because the distribution might be different, it liberates certain people from ever having to actually change their minds based on new information, because they can just posit a different distribution that satisfies their own biases.

Re: Averaging is a convenient fiction of neuroscience

#54

Post by Jweb_Guru »

mcmoor wrote: post #14
_yb2s wrote: post #7

I've become increasingly convinced that the idea of averaging is one of the biggest obstacles to understanding things... it contains the insidious trap of feeling/sounding "rigorous" and "quantitative" while making huge assumptions that are extremely inappropriate for most real world situations. Once I started noticing this I can't stop seeing this almost everywhere- almost every news article, scientific paper, etc.…

It's just trying to assume normal distribution when it's not normal. Modern science rely so much on that distribution that i actually whether they have overestimated its ubiquity just because it's so damn convenient to use.

While it is true that not all distributions are normal, many distributions are approximately normal (or at least, normal in some sensible space that maps onto the actual collected data). IMO the amount of ink spilled on the idea that science is fundamentally flawed because distributions aren't always normal is probably too high (especially among non-statisticians), and frankly that's not where statistical analyses usually go wrong. A much larger problem (that has nothing to do with the ultimate shape of the distribution) is stuff like postselecting from a set of plausible models until you find one that finds significant results, and claiming that was what you intended to measure all along (this is why it's important to consider stuff like hyperpriors, much moreso than lack of normality).

Re: Averaging is a convenient fiction of neuroscience

#55

Post by ggm »

JumpCrisscross wrote: post #31
ggm wrote: post #25

Earlier quoted context omitted.

> But unless you have a way to interpret the high-frequency signal, it looks an awful lot like noise. In other words, they're looking for their lost keys under the lamp-post because it's easier there. If there is a signal in the HF, it's not yet understood. This feels like "junk DNA" -which is I believe receiving more attention than the name suggests.

> they're looking for their lost keys under the lamp-post because it's easier there This is a strange criticism. If you're looking for your keys in the dead of night, and there is a lamp post where they might be, you should start there. The streelight effect criticises " only search[ing] for something where it is easiest to look" [1]. Not searching where it's easiest in all cases. In this case, we know averaging dest…

Good point.

Re: Averaging is a convenient fiction of neuroscience

#57

Post by robwwilliams »

RaftPeople wrote: post #39
robwwilliams wrote: post #13

Great note Mark. I agree. Action potentials are noisy beasts but much may be hidden in spike time coding that is obscured by averaging. There is an even lower level problem that deserves more thought. What timebase do we use to average, or not. There is no handy oscillator or clock embedded in the cortex or thalamus that allows a neuron or module or us to declare “these events are synchronous and in phase”. Our notio…

> There is no handy oscillator or clock embedded in the cortex or thalamus that allows a neuron or module or us to declare “these events are synchronous and in phase”. Brains waves drive synchronization of groups of neurons, lower frequencies broader, higher frequencies more localized.

That is uncertain. They must be a product of underlying processes, but the mechanisms are still opaque.

Gamma oscillations only run at about 40 Hz. That is not fast enough to clock neuronal computations or integrations in the 1 to 10 msec range.

Oscillations may have role in binding at larger scales. And when we use the word “synchronize” we generally seem to mean “given wall-clock time”.

Two neural events separated by 20 msec can be functionally coherent but may neither be in a particular phase relation or concurrent from an observer’s wall-clock perspective. Neuronal activity may not care about the observer’s timebase.

Re: Averaging is a convenient fiction of neuroscience

#58

Post by robwwilliams »

heyitsguay wrote: post #5
glial wrote: post #3

All models are convenient fictions. I heard a neuroscientist once describe averaging as a low-pass filter. People know it hides high-frequency dynamics. But unless you have a way to interpret the high-frequency signal, it looks an awful lot like noise.

My grad school research was with an NIH neuroscience lab studying low-level sensory processing that offered a fascinating perspective on what's really going on there! At least for the first few levels above the sense receptors in simpler animal models. To oversimplify, you can interpret gamma-frequency activity as chunking up temporal sensory inputs into windows. The specific dynamics between excitatory and inhibitor…

By “low level” do you mean in the thalamus or cortex or something else. Live a citation. I initially thought that “low level” meant at the level of receptors and the first few synapses. But to the best of my knowledge gamma oscillations will not play a roll in the periphery.

It would be great if you had a citation. I have been reading Karl Friston’s work all day.

Re: Averaging is a convenient fiction of neuroscience

#59

Post by zmgsabst »

hifromwork wrote: post #48
dalmo3 wrote: post #46

Earlier quoted context omitted.

I came to the same realisation about a decade ago, after being a "science" enthusiast growing up. As you said once you see it you can't unsee it. Most of science is just a scam. The exceptions are those fields backed up by real world engineering. All of social and most of biological sciences are worse than useless, they are outright dangerous.

>Most of science is just a scam Most of the scientists are not scammers. So if you believe that all science disciplines other than engineering are wrong[1], you should use another word that doesn't suggest researcher malice. [1]Which is a very strong statement, because you claim to be an expert in all science disciplines at once.

I think there’s clear evidence that a sizable portion of “science” is indeed a scam for prestige and funding.

https://en.wikipedia.org/wiki/Replication_crisis

Re: Averaging is a convenient fiction of neuroscience

#60

Post by llm_trw »

_yb2s wrote: post #52
llm_trw wrote: post #49

Earlier quoted context omitted.

>What you said in no way conflicts with what I said. Neither would a world with 88 people with the following death schedule. | Age | Deaths/Year | |---------+-------------| | 0 to 5 | 2 | | 5 to 70 | 1 | | 70 | 3 | I'm sure that the 3 people who make it to 70 are very happy they are in the highest mode of the distribution. The 85 who did not may have something to say about how meaningful using the mode of a distribut…

It’s the right thing to use in this specific context not because it is explaining the full picture better than the average, but because it distorts the picture in a different way: the modal age being high is incompatible with the incorrect assumption people are making when seeing a low average life span- that people in ancient times basically never made it to an old age in their 70s or older. People then jump from th…

>because it distorts the picture in a different way: the modal age being high is incompatible with the incorrect assumption people are making when seeing a low average life span- that people in ancient times basically never made it to an old age in their 70s or older.

I literally proved by demonstration why having a distribution with an absolute mode in the extreme most value means that 97% of people still died younger than that. There is nothing wrong with the assumption that basically no one made it to 70 because less than 0.5% of people actually did for any period where we have records.

>Deeper than that, I think there is a modern tendency to want to believe false claims about how awful life was in the past, and how much better we have it now… so there are a large number of such myths that are nearly ubiquitous but not accurate. Not to say that many aren’t also accurate, just that the inaccurate ones go largely unquestioned.

Again, you're wronger than the people who hold that view. I'm not sure what you're arguing against at this point other than sophistry.

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