Why Take IQ Seriously?
Nobody knows what IQ is, by which I mean that nobody knows what is the nature of the biophysical substrate underlying performance on IQ tests. There are a number of hints, though, that there really ought to be some such underlying biology.
I collect a lot of abuse from my commenters whenever I venture into the murky waters of IQ. Their predominant argument, so far as I can tell, is either that IQ doesn't exist or if it does we should pretend that it doesn't. I hear someone shouting "Pay no attention to the man behind the curtain."
The best reason for taking IQ seriously is that the world does. If you apply for a school, or a job, or join the military, you will very likely get an IQ test. These tests are prompted not by superstition but by overwhelming evidence that whatever it is IQ tests measure, that something is strongly correlated with performance - in school, on the job, and in life. That is true for such diverse occupations as offensive tackle in the NFL, machine gunner on a tank, financial analyst, university professor and bank teller.
The fact is that it's deeply foolish not to study so important to everyday life, especially since so little is known about it. At one point, IQ was thought to be something purely innate, like eye color or blood type. That belief has been shown to be false. Despite strong genetic influence, IQ has been shown to be affected by education and life experience. Perhaps a more apt comparison would be with adult height, now known to vary by nine or more inches depending mainly on childhood nutrition. The brain, of course, retains its plasticity long after bone growth plates have shut down further action.
So, go ahead and ignore IQ if you like - the world won't.