I’ve seen a few citations this week of a study showing a 3 IQ point per decade drop in men’s intelligence levels: https://www.sciencealert.com/iq-scores-falling-in-worrying-reversal-20th-century-intelligence-boom-flynn-effect-intelligence
I’m not qualified to judge the merits of the study, but it is interesting if true, and since it is based on studying 730,000 men and seems to use a sensible methodology, it does sound reasonable.
I wrote last November about the potential effects of environmental exposure to hormone disruptors on intelligence, pointing out that if estrogen-mimicking hormones cause a shift in IQ distribution, this would be very damaging even if mean IQ stays the same. Although male and female IQs are about the same, male IQs are less concentrated around the mean, so there are more men than women at each extreme.
From a social equality point of view of course, some might consider it a good thing if men’s IQ range is caused to align more closely with the female one. I disagree and suggested some of the consequences that should be expected if male IQ distribution were to compress towards the female one and managed to confirm many of them, so it does look like it is already a problem.
This new study suggests a shift of the whole distribution downwards, which could actually be in addition to redistribution, making it even worse. The study doesn’t seem to mention distribution. They do show that the drop in mean IQ must be caused by environmental or lifestyle changes, both of which we have seen in recent decades.
IQ distribution matters more than the mean. Those at the very top of the range contribute many times more to progress than those further down. Magnitude of contribution is very dependent on those last few IQ points. I can verify that from personal experience. I have a virus that causes occasional periods of nerve inflammation, and as well as causing problems with my peripheral motor activity, it seems to strongly affect my thinking ability and comprehension. During those periods I generate very few new ideas or inventions and far fewer worthwhile insights than when I am on form. I sometimes have to wait until I recover before I can understand my own previous ideas and add to them. You’ll see it in numbers (and probably quality) of blog posts for example. I really feel a big difference in my thinking ability, and I hate feeling dumber than usual. Perhaps people don’t notice if they’ve always had the reduced IQ so have never experienced being less smart than they were, but my own experience is that perceptive ability and level of consciousness are strong contributors to personal well-being.
As for society as a whole, AI might come to the rescue at least in part. Just in time perhaps, since we’re creating the ability for computers to assist us and up-skill us just as we see numbers of people with the very highest IQ ranges drop. A bit like watching a new generation come on stream and take the reins as we age and take a back seat. On the other hand, it does bring forwards the time where computers overtake humans, humans become more dependent on machines, and machines become more of an existential threat as well as our babysitters.