Iron makes people crazy and retarded. Not lead. People used to be exposed to so much lead that their skin got blue tinged at the time of the fastest progress in history. The increase in crime and violence only started after iron was supplemented and every place where food gets "fortified" sees crime, riots, violence, and decay.
Chinese children usually need to be taught they really shouldn't cooperate with some people.... Western children need to be taught it might be sometimes worth to cooperate, so they learn to cooperate on hurting others. It's neither genetic nor cultural, and it's hard to disentangle which metal does what, since they compete for a single transport, but too much iron / too little lead, copper or cadmuum seems to lead to a sort of brash, insensitive and generally unfriendly and toxic personality.