When you say "function", do you mean how far it can take an individual or how high an IQ is? Or can be? If the former, as in how far, I agree. IQ is. Although an individual can improve his test scores, he can only get so high, once his "limit" has been reached. We can all learn teh subject matter being tested, but at some point, we reach our limit of understanding and ability to apply or recall it. The higher teh natural IQ of an individual, the higher the resultant score. To the point of those "diminishing returns" at which point, I would say that's your IQ. I think we see that the same way, but I believe it starts with the individual and environment exacts the full potential. Other factors unique to the individual also come into play, such as focus and discipline, but then you get those "underachievers".
Even then, I've known many folks who're very smart, can grasp and even anticipate new concepts quickly, but don't have the "education" to work some of the problems on the first battery of an IQ test. I have seen one guy score in the 130's on his first test, which isn't bad at all, then go on to hit almost 160. Which is pretty damn good.
And thanks for the tech tip. It's been awhile since I've used this board and it's tools.
Is that pic of you in USMC Class A's?