I wrote a response that argues against your hypothesis, and then I realized ... "do I really know what I'm saying? Or are these my preconceptions and biases?"
> and we know the base rate is about 10%.
Sinister.
I think it would be cool to be left-handed in a country where the language is written from right to left.
I find it interesting that the rates of a whole bunch of these uncommon-but-still-prevalent differences seem to cluster around 10%. I can't help wondering if it stems from prehistoric humans living in small group of 20-30, so each band would have on average 2-4 of each, giving the group a wider range of capabilities than they would otherwise have.
> and we know the base rate is about 10%.
Sinister.
I think it would be cool to be left-handed in a country where the language is written from right to left.