I consider those to be in the category of not lowering people's IQ. Making someone dumber is fairly easy: just drop them on their heads as a child, malnourish t

I consider those to be in the category of not lowering people's IQ. Making someone dumber is fairly easy: just drop them on their heads as a child, malnourish them, and expose them to lead and lots of parasites. And make sure they don't get enough iodine. But in rich countries we've already fixed those things, and there doesn't seem to be much else we can do.