Epistemic status: Thinking out loud.
Scientific puzzle I notice I'm quite confused about: what's going on with the relationship between thinking and the brain's energy consumption?
On one hand, I'd always been told that thinking harder sadly doesn't burn more energy than normal activity. I believed that and had even come up with a plausible story about how evolution optimizes for genetic fitness not intelligence, and introspective access is pretty bad as it is, so it's not that surprising that we can't crank up our brains energy consumption to think harder. This seemed to jive with the notion that our brain's putting way more computational resources towards perceiving and responding to perception than abstract thinking. It also fit well with recent results calling ego depletion into question and into the framework in which mental energy depletion is the result of a neural opportunity cost calculation.
Going even further, studies like this one left me with the impression that experts tended to require less energy to accomplish the same mental tasks as novices. Again, this seemed plausible under the assumption that experts brains developed some sort of specialized modules over the thousands of hours of practice they'd put in.
I still believe that thinking harder doesn't use more energy, but I'm now much less certain about the reasons I'd previously given for this.
This recent ESPN (of all places) article about chess players' energy consumption during tournaments has me questioning this story. The two main points of the article are:
First, reading the chess article led me to notice a big gap in the explanation I gave above for why we shouldn't expect a connection between thinking hard and energy consumption. In my explanation, I mentioned that we should expect our brains to spend much more energy on perceptive and reactive processing than on abstract thinking. This still makes sense to me as a general claim about the median mammal, but now seems less plausible to me as it relates to humans specifically. This recent study, for example, provides evidence that our (humans) big brains are one of two primary causes for our increased energy consumption compared to other primates. As far as I can tell, humans don't seem to have meaningfully better coordination or perceptive abilities than chimps. Chimps have opposable thumbs and big toes, spend their days picking bugs off of each other, and climbing trees. Given this, while I admittedly haven't looked into studies on this but I find it hard to imagine that human brains spend much more energy than chimps on perception.
Let's say that we put aside the question of what exactly human brains use their extra energy for and bucket it into the loose category of "higher mental functions". This still leaves me with a relevant question, why didn't brains evolve to use varying amounts of energy depending on what they were doing? In particular, if we assume that humans are the first and only mammals that spend large fractions of their calories on "extra" brain functions, then why wasn't there selection pressure to have those functions only use energy when they were needed instead of all the time?
Bringing things back to my original point, in my initial story, thinking didn't impact energy consumption because our brains spend most of their energy on other stuff anyway, so there wasn't strong selective pressure to connect thinking intensity to energy consumption. However, I've just given some evidence that "higher brain functions" actually did come with a significant energy cost, so we might expect that those functions' energy consumption would in fact be context-dependent.
Second, it's weird that what we're doing (mentally) can so dramatically impact our energy consumption due to elevated heart rate and other stress-triggered adaptations but has no impact on the energy our brain consumes. To be clear, it makes sense that physical activity and stress would be intimately connected as this connection is presumably very important for balancing the need to eat/escape predators with the need to not use too much energy when sitting around. One doesn't yet make sense to me is that, even though neurons evolved from the same cells as all the rest of our biology, they proved so resistant to optimization for variable energy consumption.
The best explanation I can come up with for the two puzzles I just discussed is that, for whatever reason, evolution didn't select for a neural architecture that could selectively up- and down-regulate its energy consumption depending on the circumstances. For example, maybe the fact that neurons die when they don't have energy is somehow intimately coupled with their architecture such that there's no way to fix it short of something only a goal-directed consequentialist (and therefore not a hill-climbing process) could accomplish. If this is true, even though humans plausibly would've benefited at some point during our evolutionary history from being able to spend more or less energy on thinking, we shouldn't be surprised never happened.
Another weaker (IMO) explanation is that human brains do use more energy in certain situations for some "higher mental functions" but it's not the situations you'd expect. For example, maybe humans use a ton of energy for social cognition and if we could measure the neocortex's energy consumption during parties, we'd find it uses a lot more energy than usual.
Got it! then I agree with you. I think that a best description of my point would be that yeah, these guys are not burning calories by thinking better or harder. Their exercise plus the higher stress environment could account alone for their high amount burn of calories.
In light of reading Hazard's Shortform Feed -- which I really enjoy -- based on Raemon's Shortform feed, I'm making my own. There be thoughts here. Hopefully, this will also get me posting more.