“Having talent is like having blue eyes. You don’t admire a man for the color of his eyes. I admire a man for what he does with his talent.”
– Anthony Quinn, Actor
Are people with blue eyes more intelligent? Generally, it seems that we hold positive connotations of blue eyes. Memes are created like the one above suggesting people with blue eyes are destined for greatness. A popular political movement in the 20th century even exalted people with blue eyes as being superior. And of course, we should not forget the iconic Yu-Gi-Oh card, Blue-Eyes White Dragon.
When I asked my Twitter followers this question, they were overwhelmingly likely to think people with blue eyes were more intelligent. And if there’s one thing Psychology has taught us, it’s that stereotypes are rarely wrong. Yes, that group runs faster, that group commits more crimes and that group appears to run the media, the banks, academia and politics. Of course, I’m talking about men!
Some people, with this idea of blue eyes, have even tried counting the number of eminent people with blue eyes. Supposedly, 35 out of 46 US presidents have had grey or blue eyes. Making the generous assumption that each president has a 50% chance of having blue eyes, there is only a 2 in 10,000 chance of such an extreme outcome. Of winning quarterbacks at the Superbowl, 80% have had blue eyes. No one has published a peer-reviewed paper estimating the eye colours of eminent people, so I’m reluctant to trust these figures. Even if they were true, there’s a kind of survivorship bias, we are not going to hear about all the fields where only 40% of the winners have blue eyes.
Of course, we would expect eye colour to correlate with IQ in the wider population since it is confounded with ancestry. But there is some reason to suppose it might correlate with IQ even just within white people. Northern Europeans tend to be smarter than Southern Europeans who are less likely to have blue eyes. More generally, latitude correlates with IQ, skin colour and melanin, which in turn partially causes eye colour. There’s also assortative mating – perhaps the smartest men manage to secure the most attractive ladies who have blue eyes. This would cause eye colour and intelligence to go together. There’s also pleiotropy, perhaps the genes for eye colour actually cause intelligence?
But that’s enough speculation – what does the data on eye colour and IQ say?
Estabrooks (1929) found that in a sample of 887 white school children, the blue-eyed had a median IQ advantage of 4 points! That’s big. So he tried again with a smaller sample 324 school children and found this time the brown-eyed children had a 5-7 point advantage. Overall, doesn’t look like much is going on.
So when is the next study done? Well, it would take nearly 100 years later. A couple of studies looking at the effect of racial admixture on IQ, would control for physical features to see if racism was causing minorities to have lower IQ. One of their methods was to estimate eye colour probabilities from each individual’s genetics. The first time this was tried (Lasker et al., 2019). They used 6 SNPs for eye colour, which sounds pretty bad since many more variants for eye colour have now been found. But their method of estimating eye colour has an ‘AUC’ (area under the curve) of 0.94, implying it can correctly guess whether or not you have blue eyes 94% of the time. That sounds pretty darn good!
Unfortunately, only 3% of the sample had the right genes for eye colour to be estimated so this result is not even reported in the paper but in the supplement. The results may be biased and the sample size was now 141. But this result did find people with brown eyes were smarter (p < 0.01).
The best test would come with John Fuerst et al’s 2021 paper. They estimate eye colour in the same way, but this time all the sampled genomes had the right SNPs available to estimate eye colour. In the appendix they limit their tests to just self-reported white people and show this:
In a regression of IQ, with a large sample of people, they control for the probability of brown eyes and probability of “intermediate eyes” and find no significant effect. They were obviously testing for the effect of ancestry, not eye colour so the method is not quite what we’d want. Because the genetics of eye colour differs somewhat between races, we’d only want 100% white people. We’d want to remove variables like “discrim_fact” asking people whether they have ever been discriminated against – low IQ whites are more likely to say yes. We’d remove skin colour and hair because it’s multicollinear with eye colour. We’d also just use the probability of having blue eyes, rather than the probability of brown and the probability of intermediate, which would give the test more power.
Overall though, these factors probably don’t change much. It does not look like people with blue eyes are smarter. I’d try and get the data and do the analysis in my way, but I think the owners of this data are less likely to give it out after Fuerst et al. produced their wonderful paper.
Last research to go over – George Francis (Unpublished & Unpublishable). Before checking the genetic results I tried the test myself using a large survey of Americans – the National Longitudinal Study of Youth 1979. I removed anyone who wasn’t white and ended up with a sample size of 3111. The people surveyed took an IQ test and also self-reported their eye colour into 9 categories Light Blue, Blue, Light Brown, Brown, Black, Green, Hazel, Gray, Other.
People with light blue or blue eyes were 1.5 IQ points smarter than others (p < 0.01). If we include grey as a blue eye colour then the difference goes to 2 IQ points. I tried removing the ‘other category’ and nothing changes. I even tried controlling for self-reported European ancestry (English, German, French etc.), the difference goes from 1.5 IQ to 1.3 IQ with a significance of p < 0.05.
On their own, my results might suggest that blue-eyed white people really are smarter than others. Self-reported European ancestry is hardly a perfect measure, but the regression results even suggest blue-eyed white people have higher IQs due to assortative mating or pleiotropy rather than ancestry.
So why do my results differ from the genetic results of Fuerst et al? Maybe my results are a fluke. The biggest problem is that they rely on self-reported measures, are all “White” people of “Irish” ancestry really as White as they claim? At least 3.5% of White Americans today have some African ancestry. That doesn’t sound like much and it would have probably been lower in our 1980 sample. Maybe some people just don’t know what their eye colour is. More generally, you can never trust people to be truthful in surveys.
Whilst Fuerst’s study was not designed with the purpose of testing whether blue eyes predicts intelligence in white people, his sample size is twice as big as mine and does not use self-reported eye colour. Of course, across all Europeans, some nations will really be smarter and they will have different frequencies of eye colours, but in the 50% or so of Americans who are still White, eye colour probably does not predict intelligence. And if it does, it will probably be less than 1 IQ point difference.
For the record, if the theory is ever properly tested using a rigorous measure of eye colour and IQ, including only Americans with 100% European ancestry and a sample size of 5,000+, I predict a 35% chance of people with blue/grey eyes having an IQ 0.5+ points above other White people.
Anglo Reaction 