Source: Astral Codex Ten
by Scott Alexander
“Neuron number predicts animal intelligence better than most other variables like brain size, brain size divided by body size, ‘encephalization quotient,’ etc. This is most obvious in certain bird species that have tiny brains full of tiny neurons and are very smart (eg crows, parrots). Humans with bigger brains have on average higher IQ. AFAIK nobody has done the obvious next step and seen whether people with higher IQ have more neurons. This could be because the neuron-counting process involves dissolving the brain into a ‘soup,’ and maybe this is too mad-science-y for the fun-hating spoilsports who run IRBs. But common sense suggests bigger brains increase IQ because they have more neurons in humans too.” (03/06/25)
https://www.astralcodexten.com/p/why-should-intelligence-be-related