Recently, I came across a study which found that vegetarians are more intelligent. It sounded like one of those pseudo-science health articles, and I didn't pay too much attention to it... until one too may idiot quoted it to me. This report in particular seems to be some kind of moron-magnet.
Figured I'd do some poking around and see what exactly the report was trying to say. The first thing I found obviously was that the conclusions were being misquoted. The report actually states that intelligent children are more likely to become vegetarian later in life. This is quite different from a vegetarian diet making you smarter. Quite the reverse, in fact. It is saying intelligence leads to vegetarianism, not the other way around. Obviously, most mainstream media ("Don't bother thinking - we will draw your stupid conclusions for you.") could not be bothered with trifling details like these.
There's more. The actual report is a classic example of how setting out with a narrow objective can cloud your reasoning. What the researchers set out to do is to find a link between vegetarianism and IQ. What they did do was re-discover something obvious -- that intelligent people are more likely to make choices which set them apart from the herd.
Support for this comes from the other findings in the same report. For instance, there was no difference in the IQs of people who were truly vegetarian and the ones who called themselves vegetarian but ate chicken and fish. Calling yourself vegetarian seems to be more indicative of your intelligence than actually being vegetarian! Understandable again - as it is this willingness to be different which points to you being intelligent, not what you actually are, or (heh!) what you eat!
The surest sign of intelligence is a tendency to try and analyze facts for yourself and draw your own conclusions. Naturally, this implies some of the people who think for themselves would conclude the prevailing school of thought is wrong. You check the IQs of people in this group, and obviously you'll find they are higher than average. However, with just this data, there is no way of concluding which school of thought is "correct". Sure, the number of intelligent people in a group that stands apart from the crowd will be proportionally higher. But an equal or maybe even larger number of intelligent people, faced with the same facts, might have concluded that the majority is right in this case.
366 of the 8210 test subjects in this study have chosen to be counted as vegetarian. It is perfectly possible that an equal or higher number are non-vegetarian by choice. It just happens that their choice puts them in a group dominated by people who do not have the intelligence to analyze facts for themselves and hence find it easier to blindly follow what everybody else does. This does not mean intelligent people tend to become vegetarian, as the researchers concluded. The fact is, there is no correlation at all, at least based on the findings in this report, between diet and intelligence.
The study was conducted in a primarily non-vegetarian country (United Kingdom) with the majority of the subjects being non-vegetarian (7844 non-vegetarians and 366 vegetarians). It is no surprise that the average IQ of the vegetarian crowd is slightly higher than the non-vegetarian crowd. There are people who have chosen to be different -- obviously they are more intelligent. What would be more interesting would be to conduct the same survey in a primarily vegetarian society -- parts of Northern India, for instance. The numbers would almost certainly be inverted, with the group which bucks tradition by being non-vegetarian having the highest IQ.
What was actually interesting about this report was the finding that vegans had the lowest intelligence of all. Veganism, which is basically extreme vegetarianism, seems to be the choice of dumb people. Which kinda makes sense, if you think about it. Extremism of any kind is the choice of the less intelligent. It is the same thing that makes PETA and Greenpeace activists stupid while the causes they advocate happen to be quite intelligent!