Yes, I believe there is a difference in aptitudes - a great
variety.
My issue is that of the notion of intelligence as a 'thing'.
IQ tests like you said, _do_ measure something and it's
interesting to note the number. But what does it mean? Well,
several things:
a) test taking ability which includes all of the skills required
to take tests in general
b) a certain type of visual reasoning skills.
c) a certain type of skill in transforming visual metaphors into
the kind of semantic logic required to form the expected
answers.
In short, reading the minds of the intentions of the test-givers
based on scribbles on paper tongue emoticon
"How are they trying to trick me here?" was a constant question
I had in my head throughout school, including IQ testings.
I think they overuse "tricks" in testing. One of the nice things
that happened when I became an adult is that every test I ever
took for any reason after the age of 18, wasn't trying to fool
me... at least not in the sadistic manner of educational
testing.