My review says,
Plomin is optimistic that with larger sample sizes better polygenic scores will be found, but I am skeptical. Unless there are unexplored areas in the existing data sets, such as non-linearities or interaction effects, my guess is that there are diminishing returns to enlarging the sample size.
In this case Plomin is correct. Of course there are diminishing returns to enlarging the sample size — the genes of biggest effect have already been found. However, genetic mutations of negative effect are limited by selection to frequencies of about 1 in 50,000, and there are up to 9 billion of them in the genome. Collectively, they are certain to have a major impact on polygenic scores. To discover these requires millions of whole genome sequences, with associated phenotypic data such as educational achievement. Such data sets do not yet exist.
Arnold,
Could you explain your interest in the “Flynn Effect.” All of my research on this matter yields the idea that it isn’t a particularly important phenomenon. It doesn’t seem to be measuring “increases in intelligence” in the sense of “useful mental talent that can make society better.” Which is what I think people care about when thinking about intelligence. Typically something along the lines of “due to the Flynn effect, we are going to have a lot less dumb people and a lot more smart fraction people in future generations, which will lead to massive societal improvement.”
If the Flynn effect just means “people are getting better at a specific kind of IQ test that doesn’t seem to measure useful mental capacity all that well” it’s not particularly important.
Well, yes. But that’s an argument that scrambles the tribes, and can seem self-serving.
To oversimplify, there are two views of IQ. For the right, it is innate and very important. People with high IQ will generally be successful in life and in school. But you can’t really change IQ. For the left, IQ is not that important. People’s ability to succeed in life and school can be substantially changed by social programs, schools, etc.
The Flynn effect is thus potentially left, saying that IQ can change, and indeed has changed substantially. It looks like epicycles to say, “IQ matters a lot and really can’t change, but I only mean some aspects of IQ, not the parts which show the Flynn Effect. The parts that don’t change are important and the parts that show the Flynn Effect aren’t.
And of course it gets far more complicated.
We discuss IQ as a society, in terms of individual attributes, but aspects of the “Five Factor Personality Model” are salient for society. “Conscientiousness” comes to mind offhand.
A liberal society with many temptations and many need-based transfer payments seems (to me) predicated on a society in which many people are self-disciplined and industrious, with good foresight and impulse control, and a willingness to take responsibility for themselves.
If we can pound conscientiousness into people, it’s one thing.
If these things are partly heritable, it’s another.
It’s not my specialty, but posts like this raise some concerns.
https://jaymans.wordpress.com/2012/12/31/all-human-behavioral-traits-are-heritable/
I have assumed the Flynn effect is that society the last several generations have solved (nutrition, health, elementary schooling) so we have seen small generational increases in society IQ. I believe society has mostly solved the bigger things but I believe the Flynn Effect will diminish over time. (I believe some European nations, such Norway, are seeing this disappear.)
However, I do think that there is the Singapore/Sanger solution in which we are seeing societies have very slow family formation and only the really well off are having large families (3 or more+ kids) which might contributing a little bit to the Flynn Effect. In fact, the drop in US fertility is primarily come from the drop in single motherhood (45 in 2007 to 38% in 2017) and minority births, especially Hispanic-American births, have dropped a lot since 2008.
The Flynn effect occurred in the developed OECD throughout the second half of the 20th century. This despite the fact that its obvious that the nutrition and schooling problems had been solved prior to that period and didn’t change materially while the Flynn effect was happening.
According to the Flynn effect IQ in the developed world increased an entire standard deviation in the post war period. That is HUGE. If Flynn effect measured “intelligence” we would have expected the number of geniuses to soar and the number of retards to crater. We should be living in some kind of sci-fi utopia. There is no evidence of this though.
https://www.smithsonianmag.com/science-nature/are-you-smarter-than-your-grandfather-probably-not-150402883/
If the Flynn effect doesn’t really measure “actionable intellectual capacity”, then its really not that important a counterpoint as Arnold referred to in his final paragraph.
If the Flynn effect just means people are getting better at one thing, but worse at others, that would be less interesting than if it means they are getting better at everything. But it would still be interesting! To a scientist, at least.
I think which of those is happening is an open question. The Flynn effect could mean that people got better at lots and lots of things during the 20th century.
If so, it behooves us to understand why. Most likely it would be due to better nutrition (remember pellagra was endemic in the US South as late as the 1920s, and that iodine deficiency during pregnancy takes 15 points off IQ) or due to better hygiene (reduced infectious disease risk from indoor plumbing, sewage treatment, and the replacement of animal transport by cars). Then it would be a one-time improvement.
If the Flynn effect is now reversing and IQ is declining, it also behooves us to understand what has changed recently to make that happen.
So there are a lot of important questions here. Is IQ a good marker for lots of cognitive capabilities, or for only a limited capability? What influences IQ? What influences cognitive capability? Can we utilize those levers to improve human welfare?
The scale of improvement in IQ seen by Flynn was very large, on the order of one standard deviation — improving any aspect of human welfare by one standard deviation would be an immense improvement. Therefore, yes, the Flynn effect is important, even if so far it’s only a clue that needs scientific investigation.
If you look at the linked story above and read what Flynn has concluded, he believes we aren’t smarter. We are just more exposed to the types of mental exercises that the tests measure.
Arnold, at the beginning of the review you discuss an example of 80% heritability of weight, but then at the end you mention 80% heritability of height. Which is correct?
“claims for the potential of polygenic scores to explain psychological traits are speculative. His claims may turn out to be correct, or they may not. Either way, the ongoing research is very important.”
I find these claims, like so much infotainment, very interesting, but not very important. Because there is clearly some, even a lot, of polygenic heritability to all the traits we all have. But what’s very important is behavior.
We want to encourage good behavior, and discourage bad behavior. If we are more successful, we will have a better future than if we get less good and/or more bad behavior.
Today, our society can’t even agree on what is good behavior, which kind of makes better knowledge of whether IQ is 50%, 20%, or 80% inherited much less important.
Those with low math SAT scores probably shouldn’t spend too much time learning to code, tho.
“The heritability of divorce is about 40 percent across studies. This is a long way from 100 percent, meaning that non-genetic factors are also important. However, the major systematic factor affecting divorce is genetics. In contrast, no environmental predictors of divorce have been identified in research after controlling for genetics.”
Perhaps if Plomin chose to apply “polycultural” influences to his analysis, he would see some predictors.
Consider that India has a 1% divorce rate. The country’s diaspora may also have very low relative rates of divorce, but they clearly don’t hold to that low a rate when their children are born and raised in Europe and the Americas.
I recommend reading Determination of Nonlinear Genetic Architecture using Compressed Sensing, Chiu Man Ho & Stephen D. H. Hsu (2015)
Or much more accessible, here is Stephen Hsu at the The Paul G. Allen Frontiers Group explaining the non-linearities and showing he predicted the size of the dataset needed for height:
https://www.youtube.com/watch?v=8EjJ5VaJ0fw&t=2131s&list=PLwvbtK3tPPjBALhcYKLUZqZgz3cxl-fCm&index=11
Stephen Hsu’s blog is well worth following – http://infoproc.blogspot.com/