Agreed. You have to be careful to remove bias. For example, if I set up a scientific study that compares the intelligence of vegetarians to meat-eaters I may

Agreed. You have to be careful to remove bias. For example, if I set up a scientific study that compares the intelligence of vegetarians to meat-eaters I may find vegetarians scoring higher on intelligence than meat-eaters but that wouldn't necessarily prove the points that I speculated about above. That's because meat is subsidized, so people in poverty would have a harder time being vegetarian, and I would think that poverty is correlated with education level which would be correlated with intelligence. (See http://www.pcrm.org/magazine/gm07autumn/health_pork.html http://www.pcrm.org/magazine/gm07autumn/health_pork.html)