why do people consider blondes air heads?

in what way is this a question with historical relevance?

I suspect, as i've posted in your other post as well, it mostly has to do with DYED blonde hair.
Blondes that are dyed tend to be superficial, because they care most of their appearance. Dyed hair is not a new discovery, it has existed for hundreds (if not thousands) of years.

If you have to ask you're probably blonde.

Originally posted by Styrbiorn     Maybe Hollywood has something to do with it.

Why?

Simply envy.

Brunette girls simply envied blonds, so they invented that urban myth.

The California blond probably got the thing rolling, the type of girl who takes pride in being stupid. I'm afraid I've met too many stupid blond people, methinks there is strong science behind it...

No idea.

The great irony is she is perfectly correct in almost everything she says if taken in a certain context.

Originally posted by Paul No idea.   http://www.youtube.com/watch?v=ANTDkfkoBaI

"I'm not even sure France is a country?"

"I've heard of Turkey, but....!"

"I thought Europe is one country?"

Yes Paul, in a certain context, she is correct in a twisted sort of way. I think there should be a book subject titled "The Mysterious Logic of Blond's" If there isn't one already that is? No shortage of material there - uh huh, no sir....

Originally posted by Melissa It probably has everything to do with entertainment industry, before women were prized for being very round, full figured and brunette but then hollywood came about and since back then woman were depicted as mental children, 95% of those woman who were even aloud on TV were blondes.

I agree. If you look at fashion magazines and photos of 'ideal women' from 80 years ago the desired qualities of women were quite different.
I think hollywood is largely to blame.

Originally posted by Reg The image is also distorted further by men who, finding blonde girls attractive, want them to be stupid so they will be easier to get in bed with. It's a male fantasy you often find in movies, which coinciding with what I mentioned above reinforces the stereotype.

That is also possible, or at least a contributor.

Originally posted by Reginmund Of course in reality there is no connection between naturally light hair and low intelligence. On the contrary, the north European countries (including colonial countries outside of Europe proper) rank among those with the highest average IQ and level of education in the world.

Recognising of course that you were just defending your hair colour group from what's essentially racism, and that both your sentences are in a very strict literal sense correct, I have to point out that the second sentence is statistical nonsense. The equal and opposite shitistic would be to say that as evolution teaches us that a animal with a superior genetic mutation will be more successful, and that the number of black haired people far outnumbers others, black hair is actually a mutation that drastically increases you chance of finding a mate & having kids.