Yep. And both of those correlations have plausible causations in both directions. * Higher income -> less likelihood of lead poisoning -> higher intelligence

Yep. And both of those correlations have plausible causations in both directions. * Higher income -> less likelihood of lead poisoning -> higher intelligence * Higher intelligence -> more success in job market -> higher income * Better health as a child -> better brain development -> higher intelligence * Higher intelligence -> more likely to exercise, eat healthy -> better health