What characteristics are these?
How do you quantify them?
How do you have specific measures?
Are these measures subjective in any way? How can you tell?
Are these measures affected by other factors (environmental, cultural, learning methods, teaching methods, learning environment, exposure to information relative to maturity rate)? Yes, including nutrition! Cognition is complicated. Learning more so.
How do you establish control populations to eliminate these other factors - all of them - statistically?
Assuming you find some small facet of intelligence where all of the above is possible, and then yes, it would be some small facet … how do you then correlate it with anything useful and control for those variables? Proving something is causal rather than correlated is usually harder than explaining the difference. Like with any other gene, that mutation or similar ones may already exist or spontaneously occur in other populations. This was one of my warnings on the prior physical thing. Even should you isolate a specific testable genetic component, how big a factor in the overall spread of scores? I doubt it would be huge.
In the meantime … let me measure height … easy.
Oh, have we sorted out what of the differences across populations are due to environmental things? Nope, not yet. Height is easy to measure, but growth a little more complicated.
Yes, what use is this information? How would it help someone? Except to be misunderstood by a racist?
I think it would be a fairly big waste of research money to study “intelligence”, but useful if looking for a cause of a specific, quantified disorder to consider potential genetic contributors. That may only be useful if it leads to better treatment options. But there is a lot of frivolous money spent like to research chocolate.
I know! We can use it to sell chocolate!
In one example, a Columbia University researcher, [Adam Brickman] http://www.cumc.columbia.edu/dept/taub/faculty-brickman.html), led a Mars-funded study, looking at how cocoa flavanols might affect the dentate gyrus, a region of the brain whose deterioration with age is associated with memory decline. His paper concluded that flavanols may improve dentate gyrus function, according to specific cognitive ability tests.
And that article shows the pitfalls should much of the research be funded by large sums of money invested in the outcomes. Don’t get me started on the state of research funding either.