What I’m curious about is how much of learning is active (i.e. “I want to learn this.”) vs. passive (i.e. memorizing random facts and information in passing), and what that difference, if any, looks like in the brain.
I think it’s relevant, because some people that might commonly be labeled “stupid” (in English, where the term is not as severe as in other European languages), might have the same dendritic density as an “intelligent” person, but merely specialized to the scope of their own daily challenges/context/existence.
My main point is that I suspect dendritic density might be a poor measure of intelligence on its own. The classical peasant/farmer may have the same number of dendrites as a leading expert in any academic field. Instead, maybe a better measure would be plasticity-to-permanence, where newer connections remain in place after one is exposed to new content. To that extent, I’ve personally seen professors, who when exposed to new information that may contradict their model of the world, react in ways that I would label as “stupid”.
I also have a suspicion that life circumstances would shape the observed patterns of brain activity; if someone on the lower rung of society is spending their time just trying survive each day, often through clever manipulation or complex social interactions full of nuance, maybe they would have more dendrites in order to process the variability of their circumstance. Somebody with a stable, routine lifestyle on the other hand might appear to have fewer, as they wouldn’t need to be in constant ‘learning/survival’ mode to the extent a of a lesser well off person… not to mention differences in hygiene and nutrition between them.