Here is the abstract from a paper that appeared two years ago in Molecular Psychiatry:
Intelligence is a core construct in differential psychology and behavioural genetics, and should be so in cognitive neuroscience. It is one of the best predictors of important life outcomes such as education, occupation, mental and physical health and illness, and mortality. Intelligence is one of the most heritable behavioural traits. Here, we highlight five genetic findings that are special to intelligence differences and that have important implications for its genetic architecture and for gene-hunting expeditions. (i) The heritability of intelligence increases from about 20% in infancy to perhaps 80% in later adulthood. (ii) Intelligence captures genetic effects on diverse cognitive and learning abilities, which correlate phenotypically about 0.30 on average but correlate genetically about 0.60 or higher. (iii) Assortative mating is greater for intelligence (spouse correlations ~0.40) than for other behavioural traits such as personality and psychopathology (~0.10) or physical traits such as height and weight (~0.20). Assortative mating pumps additive genetic variance into the population every generation, contributing to the high narrow heritability (additive genetic variance) of intelligence. (iv) Unlike psychiatric disorders, intelligence is normally distributed with a positive end of exceptional performance that is a model for ‘positive genetics’. (v) Intelligence is associated with education and social class and broadens the causal perspectives on how these three inter-correlated variables contribute to social mobility, and health, illness and mortality differences. These five findings arose primarily from twin studies. They are being confirmed by the first new quantitative genetic technique in a century—Genome-wide Complex Trait Analysis (GCTA)—which estimates genetic influence using genome-wide genotypes in large samples of unrelated individuals. Comparing GCTA results to the results of twin studies reveals important insights into the genetic architecture of intelligence that are relevant to attempts to narrow the ‘missing heritability’ gap.
I’ve been doing some reading in the field, and there’s nothing particularly special about this paper. I picked it because the abstract provided a fair summary of where the literature has been for at least a generation now. In fact, I specifically avoided a couple of papers that would have seemed hair-raisingly controversial to people who haven’t looked at the literature.
My point is simple. Cognitive science and genetics are at a place that is very, very different than most people think. And the science is getting better, faster and more precise. I believe it is, in fact, fair to say that we are in the early stages of a revolution in the biological sciences, particularly where it concerns the study of intelligence and other mental traits.
So what is going on? Why does the science seem so alien in 2017 America? To quote no less an authority than Steven Pinker:
Irony: Replicability crisis in psych DOESN’T apply to IQ: huge n’s, replicable results. But people hate the message.
As a complete outside, I wouldn’t dare argue the science with Pinker. Still, his statement is partly wrong. Sure, most people hate the message. But some people love it. The people who love the message love it because they can use it to justify the hatred in their heart. The rest of us hate it because we understand what it implies. If intelligence and other personality traits are largely heritable, people aren’t a blank slate. It casts doubt on many of our cherished myths. More disturbingly, it almost implies people have some sort of destiny, one that wouldn’t be out of place in a Gattaca world, or worse, a Brave New one.
Of course, if something along those lines were the case, it would be useful for the majority of the body politic – say, the center left, the center, and the center right – to develop ideas and policies for how to deal with it in a way that fits our values. Instead, a monopoly on that sort of discussion has been granted to the haters… and you can well imagine the policies they have in mind. For everyone else, such topics are now mostly taboo. They can be discussed in a lab setting, in technical terms, but woe betide anyone, including a biologist who translates them into the vernacular.
But what if it turns out that the actors, attorneys, community activists, educators, HR professionals, journalists and liberal arts professors are wrong? What if the world’s most pre-eminent cognitive researchers, geneticists and neurobiologists know the science better than they do? What if traits like intelligence and behavior are transmitted very much as described in the scientific literature? I know. It sounds nuts. But what if? What would we do then? In such a world, what policies should we set? And how do we ensure that those are the policies that actually do get enacted?
Update. Corrected link to abstract.