There is a review article in molecular psychiatry on intelligence. Yes, it is inherited. To quote.
Quantitative genetic research on intelligence indicates that the genetic causes of high intelligence are quantitatively, not qualitatively, different from the rest of the distribution. A recent study of 11000 twin pairs found that the top 15% of the intelligence distribution was just as heritable (0.50) as the rest of the distribution (0.55).83 Most recently, in a study of 370 000 sibling pairs and 9000 twin pairs in Sweden from 3 million 18-year-old males whose intelligence was assessed as part of compulsory military service, not only was high intelligence (top 4%) just as familial and heritable as the rest of the distribution, a method called DF extremes analysis suggested that the same genetic factors are at work.84 DF extremes analysis focuses on the genetic causes of the average difference between an extreme group, however defined, and quantitative trait scores for the population, comparing the differential regression to the population mean for the co-twins of identical and fraternal twin probands.85 To the extent that genetics is found to account for this average difference (called ‘group’ heritability), it implies that there is a high genetic correlation between the extreme group and the quantitative trait.60 In the Swedish study, DF extremes analysis showed that genetics explained about half of the mean difference between the high-intelligence group and the rest of the distribution, which was similar to the traditional heritability of individual differences and implies strong genetic links between high intelligence and normal variation in intelligence.
It is possible that scores more extreme than the top 4% of the intelligence distribution are aetiologically different from the normal distribution, which has been called the Genetic Discontinuity Hypothesis. The most persuasive argument for genetic discontinuity for extremely high intelligence was made by David Lykken who noted that a key problem of genius is ‘its mysterious irrepressibility and its ability to arise from the most unpromising of lineages and to flourish even in the meanest of circumstances’. Lykken, 88 proposed that genius emerges from unique combinations of genes; he referred to these higher-order nonadditive (epistatic) interactions as emergenic. The emergenesis hypothesis does not necessarily predict that different genes affect high intelligence, but it does predict that genetic effects are non-additive for high intelligence. The hallmark of an epistatic trait is one for which identical twins are more than twice as similar as fraternal twins. However, in the two twin studies described above, high intelligence did not show this pattern of twin results and model-fitting analyses found that all genetic influence was additive for high intelligence as well as for the entire distribution of intelligence. Although these results do not support the Discontinuity Hypothesis, the studies were limited to the top 15% and top 4% of the intelligence distribution, which is far short of the extremes of genius, which Galton89 benchmarked as the top 0.1%
From my point of view the associations within the tests are, if anything, more interesting. For the bulk of the population you can probably collapse all four factors into one, and the “g” or General intelligence model works.
But… what happens at the high end. Three standard deviations from the norm: an IQ of around 145 on most scales. This is speculation, but from looking at people smarter than me, there are gaping holes. The mathematical may be scholarly, but not verbally fluent. Things do not align perfectly. The correlations are not complete. This needs to be replicated with the highly intelligent.
The trouble is that most of them are not in the groups, such as MENSA, which claim to represent the very bright. Because those organizations, to perpetuate themselves, require a greater population, and stop dealing with the weird and abstruse.
Forgetting, that for most fairly bright people, the weird and abstruse are where the fun is.
It’s always weird to explain to people that the version of the conversation we should have had was a lot more interesting, when I played it all out in my head. I find this reality tends to make dealing with young children a lot easier than adults, as you don’t have expectations of children. And adults can read when you’re treating them as ignorant, so there’s a learned skill that you need.
Still, the problem with “g” has always been that it’s a pretty bad concept for what it’s trying to measure. There are simply different vectors & approaches that people have as a natural course. For the analytical types, there is an Engineer mindset that compares to an Analyst mindset. Both can arrive at functional answers to questions, but their entry points are always different. It’s a bit like the difference between Newtownian & Leibnitzian Calculus: each version has its strengths, but they are very different approaches to the same problem.
And that’s before we approach it from a neurological structure point of view. There’s very definitely a few different ways that the really intelligent process information, likely focusing more heavy on specific structures that they’ve built up over time, as they found it more valuable to focus on those mental skill sets over others. Which then opens up the Prodigy vs Genius issue, where the Prodigy just “knows stuff” while the Genius has a hyper-focus ability, thus allowing them to accrue vastly more hours on a complex subject over their piers.
It’s actually a pretty fun topic, but, well, it helps to be really smart, otherwise it simply comes off as arrogance.
Speaking as one who makes a brick look thin, I’m always puzzled by the genii who lack common sense. It doesn’t neccessarily accompany wisdom either. Top gun in this arena is, upon reason of scripture, Solomon. He builds the kingdom to its zenith, kings come from everywhere to listen, look and marvel and the dude plays the rabbit and takes up with hundreds of harpies . Beyond the throne room, his domestic life must have been hell. You’d think a man would learn by wife number 20 or 30…
Then I read of a man like prof of maths Alec Aitken. Despite being nearly blown to chops on the Somme his prodigious memory and maths brain went from strength to strength, He was a musician, a gifted linguist,athletic, humourous and personable. He was probably full of common sense too. Some people shouldn’t have a superiority complex, They really are superior.
I’ll go back to breathing through my mouth, jaw a-slack.