Vegetarianism and IQ

According to this study published today in the British Journal of Medicine, "Higher IQ at age 10 years was associated with an increased likelihood of being vegetarian at age 30." The study gathered data from 8,170 men and women 30 years of age who are ongoing participants in the 1970 British cohort study. The study also found that: "IQ remained a statistically significant predictor of being vegetarian as an adult after adjustment for social class (both in childhood and currently), academic or vocational qualifications, and sex."

The study itself doesn't explain why individuals with higher IQs are more likely to be vegetarians as adults, but Catharine L. Gale, the study's lead author, cites as a possible explanation the general tendency among brighter children to behave in a healthier fashion as adults. As Gale notes in this HealthDay report, brighter children are less likely to smoke, be overweight, or have high blood pressure and more likely to exercise strenuously. Gale thinks that her study "provides further evidence that people with a higher IQ tend to have a healthier lifestyle."

Gale's proposed explanation seems quite plausible. People with higher IQs are presumably much more likely than people with lower IQs to possess accurate information as to which behaviors promote health and which behaviors promote disease. So, even if we were simply to hold constant across IQs both the desire to be healthy and the willingness to take the steps required to be healthy, those with accurate beliefs about what behaviors are health-promoting will be more likely to engage in those behaviors compared with those who have false beliefs about what sorts of behaviors are health-promoting.

But it is also quite plausible that Gale has overlooked an important part of the explanation. Individuals with higher IQs are generally much better reasoners than individuals with lower IQs. As such, they are likely to be better moral reasoners, as well, both in their ability to identify moral reasons and in their ability to appreciate these reasons. Plus, they are more likely to be able to recognize inconsistencies in their beliefs and in their practices. If they are like most people, they believe that a world with less unnecessary suffering is intrinsically better than a world with more unnecessary suffering. Given that belief, they no doubt also believe that it is wrong to knowingly contribute to unnecessary suffering. If they are at all informed about modern animal agricultural practices, they know that raising animals intensively in factory farms greatly increases the amount of animal suffering in the world. Given their knowledge of nutrition already hinted at in Gale's reasoning above, they realize that no one needs to eat animals or animal products in order to be healthy. Quite the opposite, in fact, plant-based diets are among the most heart-healthy, cancer preventative diets one can consume. Consequently, they realize that all of the suffering and frustration that animals are subjected to in factory farms is entirely unnecessary. It serves no significant human interest whatsoever. Anyone who thinks that it is wrong to contribute to unnecessary suffering and who realizes that eating meat is entirely unnecessary has a moral reason to refrain from eating animals and animal products. I suspect that many of the vegetarians in Gale's study base their vegetarianism on just such moral reasons. If we want a complete explanation for why children with higher IQs are more likely than children with lower IQs to be vegetarians as adults, I think we must look to moral reasons in addition to self-interested health-based reasons.