Thought I'd throw in my two cents...
I took the Mensa tests at the age of 15, and got a ridiculously high score. I can say without a shadow of a doubt that it's been the biggest barrier between me and a happy life, simply because my parents began to over-estimate me - naturally seeing as they thought they had a genius on their hands. My dad was disappointed when I said I wanted to do geology. My older sister is a doctor already and he was hoping for something similar... Anyway, he was angry when I didn't bother working hard in school and just scraped enough to get into the course I wanted in college. He just kept saying that I could have gotten a scholarship and done much better for myself.
I think he's gotten over it know, seeing as I'm just about to start a Masters degree in geological computer simulations. It was still tough at the time though. I'm never taking another test, and I swore I'd never telling anyone what I got on that Mensa test. All it's done is make my life harder, and I certainly don't feel all that intelligent.
On the dimensions thing - are you actually talking about visualising 3D objects? Do people find that hard? It's weird because if I couldn't do that I'd give myself a migraine doing the simulations.
You're not talking about that, right?
The Rock Hound