It started long ago when everyone thought you could be good at Math, or good at History, or good at Science, and sometimes good at all 3.
One day Suzy(named changed and story overly simplified for explanatory purposes), a very smart math teacher, was promoted to principal. So she finally had the chance to look at students grades from every class. And she found something curious. Her students that succeeded in her Math class also succeeded at Science. And kids that did well at History, scored highly in English. So Suzy decided to call these newly discovered traits "Verbal Ability" and "Quantitative Ability" respectively.
But Suzy didn't stop there, her investigations found that Verbal and Quantitative were correlated with each other. So she invented a third trait which was the combination of Verbal and Quantitative ability and she called that g for General Intelligence. Of course Suzy wanted to measure this g with a test so she could predict(though by no means perfectly) a student's Math, Science, English, and History grades from just one score. She settled on IQ as the measure of this test, and thus IQ was born.
Basically when we give someone a whole bunch of different tests we find that if someone does well on one, they will probably do well on others. For instance if we know someone is really good at theoretical physics we know they'll be good at working memory, and solving silly matrix puzzles. But if we know someone is really good at poetry we don't know as much about how good their working memory is, or how good they are at solving silly matrix puzzles.
I've dealt with many people with advanced degrees from top tier schools who seem to be completely unable to grasp subversive or non dominant thought patterns.
For years I was stunned, thinking "how on earth could they have such impressive academic credentials and be struggling like this."
The entire institution continually fosters and rewards a set of specific things with limited application.
The rebellious person did a deeper, objective, thoughtful analysis but did worse than the obedient mimic.
Often it's a D student who knows the material the best, has the most passion for the subject, is the smartest in the class, and puts the most work in. I saw it all the time while I was TAing.
Perhaps a smart person is a rebel roleplaying as a conformist. In a game theoretic sense you get the most advantage without the penalty. It is one explanation I suspected but haven't seen for why contradictory traits might be expressed by somebody in or close to power.
> A conformist would mimic what the professor sees and pick his right one.
Less Wrong calls this 'Guessing the teacher's password'.
It's the art of mimicry. That there is no penalty for this in the education system is an indictment.
> Often it's a D student who knows the material the best
Even most A students will agree with you. There is an argument made by Alfie Kohn that grades should be abolished.
You could either solve the problems using techniques taught or you couldn't. Grades were a direct measurement of this ability. Maybe grades don't matter in Psychology or Sociology class, but I don't want to rely on an electrical system designed by the D students in my classes. It would probably kill me.
No, it does not mean that IQ scores don't measure general intelligence.
It does mean that things some people believe about general intelligence may need to be reevaluated.
> But if you can increase this with schooling, isn't it just how smart you are right now?
That intelligence (and particularly IQ) can change over time, and that there were environmental contributors to that change has been well-know for some time.
That education in adolescence is a relevant factor is perhaps new, and certainly challenges the treatment of education and intelligence as orthogonal factors that contribute to outcomes.