What I mean is that people who enjoy programming probably tend to be smart. I haven't done any statistical surveys, but the motivational feedback loop for learning programming rewards intelligence.
a) IT is akin to playing computer games all day.
b) It's easy work in a climatized office with solid pay
c) The jobs are relatively secure and abundant.
I've seen many people go into IT that would much better have been employed elsewhere, so I think that we, as programmers are not more intelligent on average than the rest of the population. I might agree that people who enjoy programming have a knack for a certain type of intelligence and problem solving ability, but I don't think that programmers are limited to the group of people that enjoy programming.
The phenomenon of the Computer Science graduate who can't write a FizzBuzz program, or even the post-graduate who can't write a simple recursive function, is well attested. But a Math student who can't handle a recursive definition is unlikely to make it through the first term.