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Maybe something along the lines of "our brains would overheat" - there's a small temperature window in which proteins won't denature, it takes k T log 2 joules to erase one bit of information (Landauer's principle), and our brain uses around 20 Watts of power.

Maybe tin foil hats make good heatsinks..

Interestingly enough there is some evidence that the Gibbs free energy of ketone metabolism is more thermodynamically efficient than glucose in the brain (c.f. Dr. Richard Veech's work). You can measure a lower temperature gradient between the tongue temperature and the brain's.

*edit: s/Beech/Veech..

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Doesn't that imply that people who live in hotter climates have...how can I put this politely?...a disadvantage when it comes to the stability of their brains? I would assume that the brain has a certain amount of redundancy, but has this ever been researched: How hot can it get before people start getting noticeably "stupider"?

Our bodies can cool themselves decently well by sweating. I think that if the climate was affecting you to the point where your brain was getting cooked, the symptom would probably be less "slightly dumber" and more "seizures and organ failure".

But I'm not a doctor or a scientist, so I could be completely wrong. Hopefully someone more informed will weigh in.

It'd make sense that there would be a mechanism for graceful degradation, no?

I think that sweating profusely and feeling thirsty is the graceful degradation. I don't think there's a way to gracefully degrade from "my brain is a burger patty now".

When diving to 90ft+ you get 'stupider' (nitrogen narcosis). Our instructor had us do simple math problems on a board underwater and timed us. We were doing them very very slowly but you don't feel that it is slower. It was an interesting experience meant to warn you that you won't realize that you are affected by nitrogen narcosis.

I've been there. It feels so good, you forget things and get unfocused

Wouldn't they not get noticeably stupider, because the observer would be getting just as stupid?

Don't worry you're not being racist, humans of all ethnicities are made of the same proteins after all. And getting too cold will affect brain function too.

Well, getting hotter than you can handle is (at least sometimes) called heatstroke. And some of the symptoms include "Altered mental state or behavior. Confusion, agitation, slurred speech, irritability, delirium, seizures and coma can all result from heatstroke." At least some of those sound roughly like "getting stupider," though it should be a surprise that a complex system doesn't respond in a simple manner to going outside of its "design limits."

http://www.mayoclinic.org/diseases-conditions/heat-stroke/ba...

There's no association of human body temperature with latitude.

So endogenous human thermal regulation is efficient enough to deal with the normal range of terrestrial environments inhabited by humans. And when it can't (if you're naked in the arctic, for example), you die.

Nope, we have that awesome homeostasis thing going on which is why our bodies (and brains) can live in such a wide range of climates in the first place.

If you get hotter than your behavioural adaptations (shade seeking, splashing yourself with water, turning on the air conditioner) plus your own inbuilt capabilities (vasodilation, sweating) can handle, then you pretty much overheat and die.

Does this also explain why people in Scandinavia+Finland seem to be so clever?

> it takes k T log 2 joules to erase one bit of information...and our brain uses around 20 Watts of power

Yet another time when my Political Science education fails me. What should I take away from this?

> What should I take away from this?

Just that you should not omit with "..." the most important part of the statement for you. You haven't studied physics. Then you see the formula and the textual name of it with the most probable entry in Wikipedia and then you throw the most useful bit for you away and ask what the formula without the name means, even though the name would give you an explanation.

pc86's quote:

> it takes k T log 2 joules to erase one bit of information...and our brain uses around 20 Watts of power

Original:

> it takes k T log 2 joules to erase one bit of information (Landauer's principle), and our brain uses around 20 Watts of power.

The explanation:

https://en.wikipedia.org/wiki/Landauer's_principle

I assumed there was some relation between k T log 2 joules and 20 Watts, probably giving some sort of context to how easily or not easily information in our brains could be lost. The theoretical principles behind the amount of energy required to erase one bit, while interesting, doesn't necessary matter for that relationship, does it?

Landauer's principle would come into effect if you had a theoretical "Computorium" material that could perfectly turn energy into computation. Then the computation you could produce per volume of space would be limited by it.

Our brains are (very) far from being the perfect computing material (so are our chips).

The theoretical minimum is only useful here to show that our brains cannot do free work. (Irreversible) computation always has a cost.

The 20 Watts are the important number. Our brains have a certain energy budget and have to perform within that constrain.

the log 2 comes from Shannon coding, because information (tm) encoding is modeled on a bit string of discrete energetic states (something quantum, too, I guess). And there is a transformation to the frequency domain (ie via discrete fourier transform). Entropy is always messured in Watt, doesn't. make sense to equate psychologic information content with physiologic enthropic consumption.

The brain has a fixed amount of energy it can use per second, and it takes a fixed amount of energy to erase one bit of information (which you can think of as performing a computation). This means that there are a limited number of computations that the brain can do in one second.

(I'll add that there's no need to make this argument from thermodynamic principles. Your brain has a finite number of neurons, and each neuron can only fire a few times a second, so that limits the number of computations that your brain can do per second as well. And that limit is a lot tighter than the thermodynamic limit.)

I was not expecting such a useful and interesting answer. Thanks!

That's interesting indeed - is there any chance there's a connection between ketone metabolism being more efficient and 'hungry intelligence'? http://www.nytimes.com/2006/12/10/magazine/10section1C.t-1.h...

Note too that digestion is an extremely energy-intensive process, so that means less glucose to the brain (etc.) So much so that humans actually lose energy digesting raw meat.

Blood seems to be a pretty decent cooling agent. Our muscles can generate a lot more waste heat and we manage to get rid of it.

It's probably not so much the blood as a whole, but rather the water in it (in fact, I would expect the other parts in blood would make the water less efficient for heat carrying capacity - but they also may have other advantages to that end).

Interesting to imagine this difference as a species which has evolved distinct specialized circulatory systems for cooling and for oxygenating tissues.

That hardly seems relevant. kT log 2 joules is something like 10^-7 times the energy of an electron. I seriously doubt that that is anything but negligible compared to the other operations brains are performing.

Did an estimate a couple of years ago that the brains estimated information processinh and the cost of 'erasing' the same amount of information under the assumption that all processed information is lost, it seemed to imply that the cost of forgetting is somewhere in the range 1/1000 of the amount of energy the actual information processing is thought to consume ( approx 8W )

It seems crazy that it can be that close given the miniscule energy information carries, to me those ~8mW is completely mind boggling big.

The most reasonable explanation is that my calculation was wrong, but at the time it did not appear to be the case, although it probablys is anyway :)

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