The evidence from simple reaction time measurements that general intelligence (g) has declined substantially over the past century or two; and the idea that modern Western Man is significantly less intelligent than his ancestors of a few generations earlier...
has provoked some responses that surprised both Michael A Woodley and myself.
Since we have further independent confirmatory scientific evidence in the pipeline, it seems reasonable to consider the non-scientific aspects of this matter in advance of further expected controversy.
On the whole the mass media was more interested in this finding than we expected - mostly because they interpreted the 'story' as a swipe at modern education or the silliness of modern pastimes; but the evolutionary psychology community (including the on-line HBD - Human Behavioural Diversity - community) was much more hostile than we expected: indeed the response took us very much by surprise.
The nature of the response - the vehement ridicule and rejection of what was a surprising but perfectly-plausible idea (of approximately one standard deviation decline in average intelligence over a span of about 150 years) made it obvious that something-else was going-on.
It was not so much that the idea of such a large decline in g over such a short number of generations was wrong - because nobody has shown any evidence that it cannot be right; nor even that the size of the intelligence decline we found might be right but implied some additional but neglected causal mechanisms - specifically an accumulation of deleterious new mutations acting to reduce intelligence in addition to differential reproductive success among people of different IQ (that being what Michael and I believe is probably happening); but that this idea of rapidly reducing intelligence was outrageous, ridiculous, grossly-incompetent - something that could not be allowed to be right.
What I think this incident reveals is some implicit but covert assumptions in the HBD community; and that these assumptions are very important to the participants - such that a challenge to them provokes the same kind of aggressive defence as would be expected from a challenge to someone's existential basis - such as a 'religion' (bearing in mind that almost all the HBD community are agnostic/ atheist and those few [just a handful, it seems] who are not atheist/agnostics, are very reticent about their religious beliefs).
I have not got to the bottom of this matter as yet, but I think there are a couple of things I can say:
1. High IQ as a virtue
High intelligence is regarded as a virtue in the HBD community - therefore to suggest that intelligence is declining is equivalent to saying that people are getting morally worse.
2. Salvation through technology
The HBD community seeks salvation through technological breakthroughs, and declining intelligence suggests that this salvation will not come.
(This belief is most obvious among explicit transhumanists; but cryto-transhumanism is very common among scientists, and pretty much the background religion of atheist modernity: the major alternative to traditional religion.)
3. Belief in progress
Belief in progress is so powerful in this group, that it seems not so much false as an outrage for modern people to be forced to acknowledge that earlier generations were (on the whole) considerably superior in some attribute which modern people deeply value - such as intelligence.
So I think the viscerally-hostile response to the discovery of slowing reaction times, and its implication of declining intelligence; is an important insight into several unexamined, but probably false, assumptions widely-held among the community of intelligence researchers and commentators.