I would be careful trying to find an explanation for why "supermodels are stupid", just because it does run into a dangerous territory of generalizations and assumptions. But it is true that society seems to hold an idea of an inverse relationship between attractiveness and intelligence, and if this is true (a big if), I'd propose the following explanation:

Part of the thinking that comes from books like Outliers or the thread lie Can One Choose To Become A Genius, is an idea that what we define as talent or intelligence or genius is the result of practice and education and, I would argue, reading. What I have notices from my own experience in our culture is that individuals defined by society as more physically attractive are more likely to pursue and be invited and exposed to social activities, hanging out with friends, parties, etc than those deemed physically unattractive, who have more time to do other things. This would go on as sort of a feedback loop, so that what seems only minor difference at the outset becomes increasingly significant with time; of course, the greater the attractiveness of the individual, the greater likelyhood and intensity we would expect of this process. There are counter arguments, such as, for example, the vast amount of people that fall outside this relationship, but since we are really concerned with the extremes (supermodels or other extraordinarily attractive individuals) the seeming exceptions do not really matter. In other words this theory only explains the extremes. I would also note that, at least in recent years, this would apply more to female children than male children (although this is changing) because it was considered socially unacceptable for girls to play video games, leaving their entertainment to reading (which I believe greatly increases intelligence) , and thus intensifies the effect.

This would explain why "party schools" are often considered to have the most attractive students (stereotypically of course). But I would still expect that in reality, this is just a large result of the selection bias. I doubt that the inverse relationship of attractiveness and intelligence would really be borne out by scientific studies. I read somewhere of a scientific study that correlates rated beauty, health, and intelligence, due to evolutionary fitness. I am still not convinced of this either though.

Interesting topic, you two. Just wanted to respond to a fragment of Mike's post:

Think of the Cat-Walk, the quintessential model walk, is to ignore everybody there and let them look at you. But without looking at the world you may become stupid.

It's a brilliant point -- I'd say not just that one might become stupid, but that something of one's essential humanity could be lost if one loses interest in looking back. To relate this to beauty, -- observing the world means looking out the window and not at the mirror.

I've also been thinking about Emily's remark that the moment Hades arrived to abduct Persephone was when she plucked the narcissus. I'll leave that pointer here.

oh boy, I am not pleased my first post here is a contrary opinion.

Being pretty doesn't make you stupid. Fact is, natural selection being what it is with wealthy men having the means to select the prettiest wives, more attractive people -we're better served to not limit this to women nor models- tend to be smarter. Really. We don't like to believe it but wealthy people tend to be taller, healthier, hgt/wgt proportionate, smarter, more fertile, happier and yes, better looking. And no, I'm not particularly attractive, not wealthy etc with the jury still out on the brains part of it.

I've met celebs and a lot of models. I noticed one thing after awhile that I didn't expect. They know a lot more than you think. They have money, they're exposed to the best of everything. They travel, they meet other interesting people. No different from us, the more you're exposed to, the more you learn. Forget what they do for a living and talk about anything, you'll find they are fascinating -which holds its own attractiveness.

As far as your cat-walk impression, it's an act. They're hangars, a backdrop, that's it. They're stage dressing to represent the image of the brand. They're hired to act the part.  I've seen some of what they have to go through. Some people might think it'd be worth, a life they dream of but for me it would be hell. Some models make a lot of money but that's about what you'd have to pay me to do it too. Only I'd never get it not having the infrastructure.