I'm sort of like Stadler. I could be a member of MENSA if I wanted to, but it doesn't appeal to me.
I didn't really act all smart in grade school; in fact, being smart is a good way to get picked on. Grade school is the last place you really want to "stand out," so I spent most of my young life trying to hide it. Although sometimes I just couldn't. My grades were terrible, but I got picked to attend a lot of those inter-scholastic science/math/spelling competitions, and I won first place city-wide (in a somewhat large city) in a few, and was the runner-up in others. I always stood out in science and math, but music class as well. High school was the same; I didn't really get great grades, and by senior year, I was doing "bad" stuff like getting stoned and/or drunk. I was offered an honors track at the college I got into based on my ACT/SAT scores, but I declined.
It wasn't until I got an extremely boring, unchallenging corporate job when I realized that I had to apply myself and act smart. But I subsequently went to grad school at the wrong time, and graduated into a terrible job market, and have been struggling ever since. I probably would have been better off staying at my old job and just sticking it out--financially at least.
IQ is a useful measure, as it generally correlates with positive life outcomes, such as more success at your job, more stable interpersonal relationships (including marriage), better at managing personal finances, etc. But it's far from a perfect correlation; in fact, at best, it explains maybe 25% of the variance in these factors. So obviously, other factors come into play, even though 25% as a single factor is more significant than any other independent variable people have found. It also loses some predictability once you get to a certain point--if you go any higher, it ceases to show additional correlation except in highly specialized fields. For example, a 160 isn't much better than a 120 for most jobs, but a 120 would be more helpful than a 100 (the approximate population mean). 160 might make it even harder for some jobs--let's just say that, in a completely hypothetical situation that never actually happened to me, you have a boss that's somewhat insecure and of very modest intelligence, it becomes hard to follow directions from someone duller than you especially if their insecurity makes it impossible for you to sincerely but constructively suggest better ways to do things even if you are right in the end. Again, completely hypothetical situation there. Such situations, though, may only make your work relationship worse, and you might just mentally check out and end up quitting and doing something else. Not all jobs are a good fit for independent-minded people.