For some reason I was thinking today about the sheer number of things I'd heard about during my wifes pregnancy and my daughters earliest months that would make our daughter dumber if we did/didn't do something.

I wonder if this conspires to make children from worse socioeconomic backgrounds dumber on average? If so, since there is still a racial income divide on average, would that mean many African Americans are stunted developmentally but that if they could just have a generation of children with proper care things would be better? (The same would apply to white trash though.)