And people still assert this is in spite of decades of the Flynn Effect.
Here's the thing: the Flynn effect seems to be a real thing, but the Flynn effect seems to have stopped in the past decade or two in developed countries. "Recent research suggests that the Flynn effect may have ended in at least a few developed nations, possibly allowing national differences in IQ scores to diminish if the Flynn effect continues in nations with lower average national IQs." http://en.wikipedia.org/wiki/F...
There's even been some reports that IQs have begun declining in developed countries. (I wouldn't put too much stock in this just yet, but it might be a good indicator that the Flynn Effect is a relic of the 20th century.)
Scores on cognitive tests have been very widely reported to have increased through the decades of the last century, a generational phenomenon termed the ‘Flynn Effect’since it was most comprehensively documented by James Flynn in the 1980's. There has, however, been very little evidence concerning any continuity of the effect specifically into the present century. We here report data from a population, namely young adult males in Denmark, showing that whereas there were modest increases between 1988 and 1998 in scores on a battery of four cognitive tests–these constituting a diminishing continuation of a trend documented back to the late 1950's–scores on all four tests declined between 1998 and 2003/2004. For two of the tests, levels fell to below those of 1988. Across all tests, the decrease in the 5/6 year period corresponds to approximately 1.5 IQ points, very close to the net gain between 1988 and 1998. The declines between 1998 and 2003/4 appeared amongst both men pursuing higher academic education and those not doing so.
There's an important genetic component to intelligence, but everything we've see recently suggests fetal development, nutrition, and education make such tremendously larger difference that the "idiocricy effect" could at most be considered a momentary blip.
Or maybe we should treat the Flynn Effect as a momentary blip.
So, what's going on? One possibility is that, in poorer countries, a substantial portion of the population is failing to get sufficient nutrition and stimulation to their children. This would have the effect of creating a portion of the population which is cognitively harmed - thus reducing the average intelligence of the population as a whole. As you get better nutrition across the entire population, you see the average IQ increase - but only because the bottom segments of society are improving (not because everyone is improving).
This would explain why poorer countries are continuing to see Flynn-effect improvements, but developed countries saw it's effect in the mid-20th century but isn't seeing any improvements lately (because the poverty that was harming childrens' brain development isn't happening anymore in developed countries).
Whatever the case, it's time to stop relying on the "Flynn Effect" as some kind of prediction that our future will continue to be bright. Here's an analogy: in the 20th century, we saw the average height of Japanese people increase significantly. This was due to better nutrition (protein, in particular, during childhood is important). We can also say that height is a strongly heritable trait. At this point, I think we should just accept that the Flynn Effect has topped-out in developed countries.
I don't think questions about declining IQs based on genetics is a bad question to ask, and I don't think 'trust the flynn effect' should be treated like it's an adequate answer. I realize I could be opening a whole can of worms, though, with this comment, because nobody wants to see a return of early 20th century style eugenics (which, by the way, was not only used by the Nazis, but was embraced in places like the United States). http://en.wikipedia.org/wiki/E...
Footnote regarding the heritability of height and IQ, which seem to be in the same ballpark, as far as heritability is concerned:
"Estimates in the academic research of the heritability of IQ have varied from below 0.5 to a high of 0.8 (where 1.0 indicates that monozygotic twins have no variance in IQ and 0 indicates that their IQs are completely uncorrelated)" http://en.wikipedia.org/wiki/H...
"How much variation (difference between individuals) in height is attributable to genetic effects and how much to nutritional effects?" The short answer to this question is that about 60 to 80 percent of the difference in height between individuals is determined by genetic factors, whereas 20 to 40 percent can be attributed to environmental effects, mainly nutrition." http://www.scientificamerican....