PhilGoetz
I have the impression of a big increase in IQ when I listen to old radio comedy shows, pre-World War II. The humor is so simple and repetitive and uninteresting that I get the feeling the US must have consisted of adult-sized children. Maybe it's because radio was a new medium; but a lot of it was just a restaging of vaudeville humor that had been successful for decades.
I have the same impression, though it could be partly due to the growth and specialization in the pop-culture market, so that the sample you happen to see today is mainly from the output targeted at smarter audiences. But the difference seems too large to explain just by that effect; the old shows are often truly mind-numbingly dull, as you describe. There was a post about this topic a few years ago on Marginal Revolution with some striking diagrams: http://www.marginalrevolution.com/marginalrevolution/2005/04/tv_and_the_flyn.html
What makes it even more puzzling is that these apparent huge increases in average folks' sharpness were not accompanied by anything similar at the higher levels of intellectual accomplishment. In many countries, a teacher or professor who taught for, say, 30 years during the second half of the 20th century would have dealt with generations of students whose average raw IQ test scores increased by more than a whole standard deviation in that period. Yet there have been no reports of striking proliferation of super-smart students at any educational level. (Consider that if the average of a normal distribution increases by 1SD, it will, ceteris paribus, boost the percentage of scores exceeding the previous +3SD threshold by about 16 times!)
So basically, we're seeing pop culture getting more mentally demanding, along with a dramatic increase in average non-verbal IQ test scores, but no visible increase in the number of exceedingly brilliant individuals. At the same time, the tests apparently remain strong predictors of all sorts of intellectual performance. I suspect that the procedures by which IQ tests are constantly re-normed to produce neat normal distributions lead to a scoring system that is seriously misleading in at least some ways. This is also a serious objection I have to a lot of research in this area: it starts and ends assuming that we're dealing with a variable (IQ) which is normally distributed through the population, like height, even though it's in fact artificially made that way, and we still have no idea what's really underneath.
The explanation that Flynn describes in his book, What is Intelligence? is basically that modern culture gives us extra practice in many of the subskills that require a lot of intelligence. That, however, doesn't increase intelligence itself - it only makes us better at doing tasks that require those subskills.
This doesn't mean that IQ tests would have lost their value, either - if, say, everyone in the population ends up exercising an additional five hours per week, then everyone's athletic ability does go up, but it's still the ones who were the most ath...
Edit: Q&A is now closed. Thanks to everyone for participating, and thanks very much to Harpending and Cochran for their responses.
In response to Kaj's review, Henry Harpending and Gregory Cochran, the authors of the The 10,000 Year Explosion, have agreed to a Q&A session with the Less Wrong community.
If you have any questions for either Harpending or Cochran, please reply to this post with a question addressed to one or both of them. Material for questions might be derived from their blog for the book which includes stories about hunting animals in Africa with an eye towards evolutionary implications (which rose to Jennifer's attention based on Steve Sailer's prior attention).
Please do not kibitz in this Q&A... instead go to the kibitzing area to talk about the Q&A session itself. Eventually, this post will be edited to note that the process has been closed, at which time there should be no new questions.