If so, why? If not, why could it have spread so much in the public consciousness? In my personal opinion, based on my experience so far, yes. I don’t mean to offend anyone with that, that doesn’t mean they are all stupid, but on average they are true. And I wondered why that might be. After all, what may the levels of eumelanin and pheomelanin that affect color have to do with brain function. I don't think it's genetic. There may be more social reasons behind it. We have known since Marilyn Monroe that blonde hair color is a kind of symbol of femininity, research also proves that blonde hair color is the most attractive for men. This is why there is a higher proportion of blondes in the models than in society, which is why brown-haired people often paint themselves blondes, but vice versa almost never, etc. It is also well known that men give a woman much more material wealth than vice versa. Why this is also an interesting question. But the point is, I have a theory that blonde girls are less intelligent because they get more attention from men, it’s easier to find a better or richer partner. Thus, even at school, they care more about passing and looking at them than learning, because in the short term, they get more "benefits." If there is a better explanation for it I would love to hear from you.