It’s the latest in the “liberals have high IQs” study series, though at least this one was carried out by real researchers, with data they didn’t make up: In one sample, kids who became vegetarians between ages 10 and 30 had average IQs of 105 (nationwide average 100) at age 30.

The most obvious explanation is that vegetarianism is a college student/high-income phenomenon, and the people most likely to get into college or otherwise make lots of money are the bright ones. College students, absurd as they can sometimes be, have higher-than-average IQs.

The way to test whether vegetarianism actually causes high IQ is this: Look at the age-10 IQs and see if they grew in the vegetarians over 20 years. (By and large, your age-10 IQ is extremely similar to your age-30 one.)

From the story:

“However, further analysis of the results showed those who were brainiest as children were more likely to have become vegetarian as adults, shunning both meat and fish.”

Higher-IQ people become vegetarians; vegetarians don’t magically grow high IQs. So although nutrition and environment in general affect intelligence (see Arthur Jensen’s work on the cumulative effect of bad homes and schools), there is no evidence vegetarianism is better for brainpower than a well-balanced meat-inclusive diet.

I don’t doubt a vegetarian eats healthier than the average person, boosting IQ by some immeasurable amount. But I don’t think there’s any difference compared to a healthy non-vegetarian.

Also, bear in mind that an IQ difference of 5 points is one-third of one standard deviation. An individual with an IQ of 105 will not be noticeably smarter than someone with a 100 IQ.

Another of the more interesting tidbits is that vegans actually have lower IQs than the average (95). Do vegans come from a different segment of the population? Or does veganism harm intelligence? Both would surprise me, as veganism is an outgrowth of vegetarianism and IQs are very hard to change.

If dairy truly is indispensable for intellectual development, it’s good news for my home state, Wisconsin.

Robert VerBruggen blogs at http://www.therationale.com and http://robertsrationale.blogspot.com.