I'm asking if there is a rational non-meta reason to believe they do "stop at the neck"
Not to my knowledge.
Are personal traits as important?
That is a more controversial subject. They are clearly less important than intelligence, but things like time preference (what kind of trade-offs do you make between a smaller reward now and a bigger reward later) or, say, propensity for violence got to be at least somewhat important.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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