I estimate that the average HBD blogger has an IQ around 124 (equivalent to a PhD) and the average HBD blog reader has an IQ around 115 (equivalent to a college graduate). But not all HBD blogs are equal. Some have much brighter readers than others. How does one determine the IQ of their readers? Well you certainly don’t ask people their IQ’s because people constantly exaggerate or selectively report their IQ’s, quite often by over 50 points! People are far more honest about their height, especially in an anonymous poll. This gave me an idea. Polling readers about their height might indirectly reveal their IQ. Of course, the correlation between IQ and height is quite weak (0.2) so knowing the height of any particular individual tells us virtually nothing about her IQ, but knowing the average height of a group is potentially revealing under certain circumstances.

Blogs select people for IQ because IQ largely determines what topics you find interesting and what topics you can understand. But when you select for IQ, whatever happens to be correlated with IQ gets dragged along for the ride. Scholar Arthur Jensen wrote about a study where mice were selected for maze solving ability. After several generations, it was found that the selection caused the mice to have larger brains. More surprising was that the maze bright mice had bigger bodies too, suggesting that the body was serving as a power pack for the brain.

Based on the anonymous poll I recently conducted, readers of brainsize.wordpress.com have a median height of six feet, which is 0.62 standard deviations above America’s tallest major demographic group (white men under 40). Why would Brain Size readers be so tall? NBA players are tall because height is an advantage in basketball, CEOs are tall because height projects leadership, but none of these selection pressures apply to people posting invisibly on a blog. Thus, the only conceivable reason why Brain Size readers are tall must be that they have high IQ’s and height is correlated with IQ. For the same reason, I would expect Brain Size readers to have large heads and a higher than average frequency of myopia, both of which are also correlated with IQ. Assuming that IQ is the only reason why Brain Size readers are tall, it’s possible to estimate their IQ’s.

The correlation between height and IQ is 0.2, and knowing that Brain Size readers are 0.62 standard deviations taller than average, then dividing 0.62 by 0.2 tells us that Brain Size readers are 3.1 standard deviations above average in IQ (IQ 147). What I just did there is called a validity generalization; for an in-depth discussion on the concept, read the comment section of this post where I discussed the topic with Michael Woodley (one of the greatest scientists in the world, in my opinion).

Given that the average IQ on other HBD blogs is 115 in my opinion, it is astonishing that the average IQ here is 147 (more than two standard deviations higher!). The average IQ at Harvard is about 130, so people here are more than one standard deviation higher than students at the most prestigious university in the world! Only one in a 1000 Americans have IQ’s of 147 or higher.

Given these facts, many will be skeptical that Brain Size readers could really be that brilliant (on average). For starters, the estimate was based on height. Even though it’s unlikely people would lie about their height on an anonymous poll, they could still be delusional. While research suggests that self-reported height is about an inch too high, we should also keep in mind that I used white males aged 20-40 as the reference group. Many Brain Size readers are either not white, not male, or not under 40, and to the extent that Brain Size readers come from shorter demographics, their heights actually underestimates their IQ, and so the estimated IQ of 147 is just as likely to be too low as too high.

I think the average IQ here really is around 147. People here are unlike commentators on any other HBD blog. Among Brain Size readers are some of the greatest scientists in the world, a child prodigy, a self-proclaimed BGI study participant, and “Pincher Martin”, one of the most learned and erudite people I have ever seen posting anywhere on the web.