Edit. I should add that the humans are not completely one population because of genetic isolation and differential selection (especially over the last 10,000 years), but we are almost a single population. Like everything in genetics it gets fuzzy at the edges.
And the very definition of "intelligence" is incredibly complex and slippery, which is one of the reasons why I've always found trying to summarise such a complex property into a single numerical value such a silly exercise.
It is: we call it "social classes". Because intelligence correlates positively with success and because people tend to have children with other people from a similar social stratum, the exact situation you described emerges as a pattern.
On reading slightly further I see someone else has already spotted this and added that disclaimer to the text.
Seems like it would be relatively easy to compare like with like here, which makes me suspicious of why it isn't done. Does that mean that the effect disappears when you do that comparison? It's certainly going to be reduced.
More on this here: http://slatestarcodex.com/2014/08/11/does-the-glasgow-coma-s...
NB I say that as someone who got a very high IQ test result - which didn't exactly convince me that IQ tests are a good idea....
Intelligence really isn't "multi-faceted" (read Gardner's own admission that his theory never panned out) and it isn't ill-understood (refer to the Nature or Nurture interview with Nancy Segal on YouTube).
There's two reasons people say that. One is, they fared badly on a test and want to dismiss it, and the other is, they fared well on a test and are bashful about it.
Also, IQ tests are meant to measure a person's intelligence, not to convince them that IQ tests are "a good idea" - for that you would have to study Psychometrics.
I know very intelligent and very stupid people all over this income range, with no obvious pattern.
Intelligence can help you gain wealth, but if you're never given an opportunity or don't have a lot of drive you'll struggle perpetually.
Not at all. There could be a specific suite of traits that includes high intelligence, present in some people but not in most. Those people would have high intelligence, but they wouldn't be the extreme of the natural variation of the rest of the population. They would have gotten there by "cheating".
This is known to occur right now in human height. Men are taller than women. The difference is so pronounced that the human height distribution is not normal. The tallest humans (except Yao Ming) basically are the extreme of normal variation in men. But they aren't the extreme of normal variation in humans.
I hope you'll agree that "men" cannot be characterized as a subpopulation that doesn't breed with the rest of humanity.
It is not uncommon to have phenotypes that are expressed only rarely although the genes that code for the phenotype are widely dispersed. Many well known genetic diseases fall into this category.
The more interesting question is which correlations are strongest. I can't find a link, but I read a study that came out a few years ago that showed the biggest correlation with financial success was the parents' income levels. That is, controlling for the intelligence of the parents, an average-intelligence person born to wealthy parents was more likely to be financially successful than an above-average-intelligence person born to poor parents.
That may also be obvious, but it has more effect on the veracity of the common view of our society being a meritocracy.
https://www.newscientist.com/article/dn12993-chimps-outperfo...
Of course, genetics probably plays a role in that, too.
I also don't think you can separate genetic influences from environmental influences, i.e. one allele might make you do well in one environment and poorly in a different environment. This appears to the case for the 7R allele of the DRD4 gene: http://www.northwestern.edu/newscenter/stories/2008/06/ariaa...
I also don't think any genes actually code for intelligence as it's commonly understood. Intelligence is, basically, knowledge (including knowledge about how to acquire knowledge). Genes affect brain chemistry, which influences intelligence in different ways, within a given environment.
But you're right that this doesn't tell you much about any of the individual dimensions. Maybe adding a variance across dimensions, so two numbers, would be more useful.
> Intelligence tests and psychometrics have generally found high correlations between different aspects of intelligence, rather than the low correlations which Gardner's theory predicts, supporting the prevailing theory of general intelligence rather than multiple intelligences (MI).[19] The theory has been widely criticized by mainstream psychology for its lack of empirical evidence, and its dependence on subjective judgement.[20]
> Intelligence tests and psychometrics have generally found high correlations between different aspects of intelligence, rather than the low correlations which Gardner's theory predicts, supporting the prevailing theory of general intelligence rather than multiple intelligences (MI).[19] The theory has been widely criticized by mainstream psychology for its lack of empirical evidence, and its dependence on subjective judgement.[20]
As for your other points...
> I also don't think you can separate genetic influences from environmental influences, i.e. one allele might make you do well in one environment and poorly in a different environment.
That's probably the case for some genes, sure. But finding strong correlations between twins raised apart would seem to indicate that many of the genetic factors are not entirely environment-sensitive.
> I also don't think any genes actually code for intelligence as it's commonly understood. Intelligence is, basically, knowledge (including knowledge about how to acquire knowledge). Genes affect brain chemistry, which influences intelligence in different ways, within a given environment.
Twin studies seem to contradict this. From Wikipedia (heritability of IQ [1])
* Identical twins—Reared together .86
* Identical twins—Reared apart .76
So yes, environment has an impact, but there's still a high degree of correlation in intelligence between identical twins raised apart.
[1] https://en.wikipedia.org/wiki/Heritability_of_IQ#Correlation...
In an modern developed economy, where you'll be more likely to do well if your IQ is high, some people will have inherited alleles which tend to raise their IQs and make them well-adapted to their environment, others different alleles which make them poorly adapted.
And, on top of that, there's an environmental, or rather cultural component.
http://www.drtomascp.com/uploads/PersonalityIntelligence_IJS...
Which seems to provide some (weak) evidence against that:
"The hypothesis of a significant correlation between various Big Five personality traits and intelligence test scores was only partially supported. Only Conscientiousness was significantly related to psychometric intelligence, correlating with BRT scores. It is worth noting that the correlation was negative, indicating that higher conscientious participants tended to have lower gf."
I'm far from an expert though, so I can't say how good that study is.
> That may also be obvious, but it has more effect on the veracity of the common view of our society being a meritocracy.
Why? There's nothing about that that speaks to how much of a meritocracy we are. Parents' financial success directly measures everything that contributes to financial success (rather than, say, a subcomponent); you'd expect it to be highly informative.
The result you cite still holds when both children are adopted away. Is that support for the view of society as a meritocracy?
I have no idea how football fairs, but you can debate the usefulness of that as an objection to the validity of IQ with someone else.
What is the True Rate of Social Mobility in Sweden? A Surname Analysis, 1700-2012 http://www.econ.ucdavis.edu/faculty/gclark/papers/Sweden%202...
In a meritocracy, as I understand the idea, one's success is based on ability and talent rather than on class privilege or wealth.
If the biggest factor in your success is your parents' wealth, doesn't that suggest we might not have a pure meritocracy?
Do you have a link to the study? I don't remember the part about it still holding true when children are adopted away. That is an interesting finding. It would support your point (I think the point you're making, at least) that it's not necessarily parents using their class/wealth to bolster their children, but instead the parents have the proper mix of traits (intelligence, grit, ability to delay gratification, etc.) that results in financial success.
Intelligence is neither well defined nor well understood. It is fairly controversial stuff.
> One thing we have to be wary of in this calculation of persistence is surname changing. If people going to the university born with the surname Anderson were changing this to Wigonius, then there would appear more persistence than there really was. The biographical sources for some of the student nations at Lund and Uppsala, Blekingska, Göteborgs, Skånska, Smålands, and Vermlands at Lund, and Östgöta at Uppsala, allow us to estimate the fraction of Latinized surnames which were newly adopted in each generation at the universities, since it gives fathers’ and mothers’ surnames for most students also. Figure 19 shows what fraction of students in each generation inherited rather than adopted a Latinized surname.18 For the earlier generations, 1730-1819, 96% of students acquired the name by inheritance from their father. However, 1820-1909 that proportion fell to 88%, even though by design these are all surnames that first existed before 1730.19 This will bias upwards my estimate of b, but can be corrected for by calculating for each period a b based just on the relative representation of the surname among the inheritors in that period.
This study does support what previous studies have found from when people looked for genes that had a large positive effect on intelligence and failed to find any.
Actually height is unlike intelligence since there is one gene on the Y chromosome that has a very large influence on height. There are no such genes for intelligence as this study and many others has found.
Nor do I. Who decides what abilities are important? How do they go about measuring them?
However, I do think it is "bad thing" for members of the elite to believe that we live in a meritocracy – when we do not, IMO. Skimming that Guardian article, I think my feeling is similar to the criticism put forth there. The notion that we live in a meritocracy creates a sense of entitlement and superiority in the elite. That is, if you believe we live in a true meritocracy, then those on top are there because they're smarter and harder working, and those on the bottom are there because they're less intelligent and/or aren't working as hard. Said more simply, meritocracy results in the feeling that you deserve your riches, and they deserve their poverty.
Whereas, in reality as I see it, your financial success is dependent on many factors outside of your control. Sure, most successful people are fairly smart and work hard, but many less successful people also have those qualities. The other factors contributing to success are things largely summed up by Warren Buffett's notion of the "Ovarian Lottery".
I'm not advocating a meritocracy. I'm advocating an honest assessment of society and the factors contributing to financial success.