We’ve all heard of the nerd stereotype. One of the main ones is that nerds wear glasses. However, as most of my readers may know, stereotypes are based on fact more often than not. From the black criminal and sprinter, to the hyper-intelligent East Asian, to the intelligent and creative Europeans, we see that these so-called ‘stereotypes’ arise because stereotypes are actually average traits. Therefore, this ‘nerd stereotype’ that they always wear glasses is based on averages, so there must be a genetic component behind it. In this article I will talk about the genetics of myopia, reasons why researchers believe it arises, and racial differences in the prevalence of myopia.
Myopia, better known as nearsightedness, has a pleiotropic relationship with intelligence. Pleiotropy is the single gene or set of genes controlling multiple, possibly unrelated, phenotypic traits. So if the two traits are correlated, then there is a good chance that if one wears glasses they may have higher average intelligence.
Rosner and Belkin (1987) found that the prevalence of myopia was higher in more intelligent and educated groups. They found a strong association between the rate of myopia, years of schooling and intelligence level. Schooling and intelligence weigh equally with myopia, showing that those who are myopic tend to stay in school longer and are more intelligent than average.
Saw et al (2004) show that there may be similar genes associated with eye growth or size (myopia) and neocortical size (*possibly* correlated with IQ, we know it is). This is exactly what Cohn, Cohn, and Jensen found in 1987; that there was a pleiotropic relationship between IQ and myopia. One set of genes controls one or multiple phenotypic traits. They also say that nonverbal IQ is correlated with myopia in the Singaporean cohort independent of near work from the children (such as reading). Nonverbal IQ may be an independent risk factor of myopia independent of books read per week. They conclude that more research needs to be taken out to untangle the cause and effect of the myopia/intelligence/reading relationship.
Mirashi et al (2014) show in a sample of 4600 myopia-inflicted Germans between the ages of 35 and 74 that about 53 percent of the sample had graduated from college compared to 24 percent of the sample who didn’t go to school past high school. They, too, conclude that higher levels of myopia are associated with higher educational achievement and post-school professional achievement and that those who were myopic had higher levels of educational achievement than those in the sample who weren’t myopic.
More recently, Verma and Verma (2015) state that there is evidence that both genetic and environmental factors play a role in the prevalence of myopia. Moreover, Czepida, Lodykowska, and Czepita (2008) come to the same conclusion; that children with myopia have higher IQs and was verified in other countries (the USA, the Czech Republic, Denmark, Israel, New Zealand).
The correlation between myopia and IQ is between .2 and .25 (Jensen, 1998 b; 149). Jensen writes on page 150:
. . .the degree of myopia was measured as a continuous variable (refraction error) by means of optical techniques in a group of sixty adolescents selected only for high IQs (Raven matrices) and their less gifted full siblings, who averaged fourteen IQ points lower, a difference equivalent to 0.92o. The high-IQ subjects differed significantly from their lower-IQ siblings in myopia by an average of 0.39a on the measure of refraction error.1161 In other words, since there is a within-families correlation between myopia and IQ, the relationship is intrinsic. However, it is hard to think of any directly functional relationship between myopia and IQ. The data are most consistent with there being a pleiotropic relationship. The causal pathway through which the genetic factor that causes myopia also to some extent elevates g (or vice versa) is unknown. Because the within-family relationship of myopia and IQ was found with Raven’s matrices, which in factor analyses is found to have nearly all of its common factor variance on g ,n it leaves virtually no doubt that the IQ score in this case represents g almost exclusively. (emphasis his)
Therefore, as noted earlier, we would see a slight variation in the general population between those with high IQs and those who wear glasses and are myopic.
Jensen also talks about race and myopia. He says that Asians have the highest rates of myopia, while blacks have the lowest rate and whites have a rate slightly higher than blacks.
In a tribute to Arthur Jensen, edited by Helmuth Nyborg, it states that East Asians have the highest rates of myopia, with blacks having the lowest rate and whites being intermediate (Rushton’s Rule of Three). Ashkenazi Jews have a rate of myopia two times higher than that of gentiles, on par with East Asians. These are yet other biological correlates with the g factor that also lend credence to the hereditarian hypothesis.
Certain types of visual disturbances affect some races more frequently. Asian-Americans, for example, are more likely to be near-sighted than Caucasians or African-Americans. African-Americans have the lowest incidence of near-sightedness, but are more prone to cataracts and some other eye diseases. Eye problems, including the need to wear glasses, also can run in families.
Of course, if myopia is a pleiotropic trait (there is good evidence that there is), and wearing glasses runs in families as well as high intelligence, it can be safely hypothesized that the two indeed do have a relationship with each other. The biological correlates show enough that these traits, too, follow Rushton’s Rule.
Finally, Au, Tay and Kim (1993) present data that shows the prevalence and severity of myopia is associated with higher education. They also report on data that Rosner and Belkin reported the prevalence of myopia in males with and IQ of 80 or less was 8 percent while the rate increased up to 27.3 among those with an IQ of 128 or higher. Reported separately, it was concluded that the myopia rates in the cohort of 110,236 young Singaporean males correlated with race (Au, Tay, and Lim, 1993). The myopia rate for the Chinese was 48.5 (IQ 105), for Eurasians it was 34.7, for Indians it was 30.4 (IQ 82), and for Malays it was 24.5 (IQ 92). It’s worth noting that India’s IQ is depressed by disease and bad nutrition, and if this were to be ratified their IQ would be around 94. So this, again, shows the biological correlate with IQ and myopia as it’s showing on the Indians’ genotype.
The association between myopia and intelligence isn’t definite yet, however with more studies looking into the relationship between these variables I believe it will be concrete that those who are more myopic tend to have higher IQs due to the pleiotropic nature of IQ and myopia. Since reading is heritable, those with higher IQs as children tend to read more as adults, and the racial gradient is noticed in children, it’s pretty safe to say that myopia and IQ are linked pleiotropically and give more credence to the hereditarian hypothesis. Most studies find a statisically positive correlation between myopia and intelligence. Along with the racial disparities in myopia as well as intelligence, it’s pretty safe to say that the relationship is genetic and pleiotropic in nature since the races also differ in these variables.