I like to use breakdancing as an example (see IQ Bashing, The Flynn Effect, and Genes). Within a particular generation, really athletic individuals will tend to score higher on a wide variety of tests that require athleticism (a trait that is influenced both by genetic and environmental factors). Athletic individuals will tend to run faster, life heavier weights, swim faster, and probably even look better breakdancing. But imagine that breakdancing suddenly became an Olympic sport (I can only dream). In this imaginary world, society suddenly shifts interest in basketball to breakdancing. We drop more money into educating everyone in the fine art of the baby-freeze, the windmill, and the headstand. Breakdancing becomes a craze, appearing in grade school classrooms, on streets, and on all sorts of job applications. What would come about as a result?

This sort of situation would up the ante on breakdancing skills. Sure, those naturally inclined toward athleticism would still have a breakdancing advantage, but the average standard of breakdancing performance would be greatly increased. In order to remain competitive, aspiring breakdancers would have to step their game up and learn increasingly complex moves. Given enough generations with such high levels of breakdancing training, you would start to see a rise in mean scores on tests of breakdancing ability.

This breakdancing example also applies to the rise seen in IQ scores across generations. Within each generation, people who tend to do well on one test of cognitive ability will tend to do well on other tests that tap to some extent complex reasoning ability. But across generations, the particular types of tests that show the most dramatic increases indicate to a considerable degree our cultural priorities. The Flynn Effect serves as a reminder that when we give people more opportunities to prosper, more people do prosper. We've come quite a long way since the pre-industrial revolution in terms of our cultural emphasis on reading, writing, abstract reasoning, and scientific thinking. The Flynn Effect is a partial indicator of this progress (see Are you smarter than Aristole?: On the Flynn Effect and the Aristotle Paradox).

Over the years, various ‘social multipliers' (Dickens & Flynn, 2006) have been proposed to account for the Flynn Effect, including increased nutrition, increased test familiarity, heterosis, increased scientific education, video games, TV show complexity, modernization, and more. Surely a combination of factors contributed to the rise. In this post, I want to focus though on a few changes over the course of the past 100 years that have particular implications for understanding race, ethnic, and national disparities in IQ. First let's look at literacy.

Literacy involves the ability to write, read, and comprehend information of varying levels of complexity. It is estimated that there are 774 million illiterate adults in the world, 65% whom are women (UNESCO Institute for Statistics, 2007). In the United States alone, 5% of the adult population is completely nonliterate (Kirsch, Jungeblut, Jenkins, & Kolstad, 1993). Self-reported literacy skills of both White and Black populations of the U.S. have been increasing steadily since 1870, however (National Center for Education Statistics, 1993). One study showed that the IQ and literacy scores of Blacks increased in parallel from 1980 to 2000 (Dickens & Flynn, 2006).

The importance of being able to read for performance on an IQ test cannot be understated. Instead of measuring ‘intelligence' in an illiterate test-taker, the test is measuring that person's inability to read. While ‘intelligence' may certainly influence an individual's ability to read, society has a lot of influence on how many inhabitants even get the chance to read in the first place regardless of the intelligence level of any single individual. Therefore, reading skills may exert important effects on particular races and nationalities that have historically undergone much discrimination and as a result, limited opportunity for literacy development.

An enormous body of evidence collected over the past 50 years shows that different ethnicities and races within a country tend to show substantial differences in their average level of IQ. Some researchers argue that this gap is narrowing (Dickens & Flynn, 2006) whereas others argue that the IQ gap has remained stable (Murray, 2006). IQ test score discrepancies are also found between nations. For instance, sub-Saharan African countries have demonstrated statistically significantly lower IQs than other nations (Lynn, 2006, 2008). These findings have led some researchers to propose that such IQ gaps found across ethnicities, races, and nationalities suggests a difference in innate brain capacity (see Lynn & Vanhanen, 2006).

Until recently, the phenomenon of the Flynn Effect, and IQ gaps found between different ethnicities, races, and nationalities have not been tied together. For the first time ever, Psychologist David F. Marks systematically analyzed the association between literacy skills and IQ across time, nationality, and race (Marks, 2010).

If increasing literacy were really explaining a number of seemingly different IQ trends, then you would expect to see a few things. First, within a population you should expect increased education of literacy skills to be associated with an increase in the average IQ of that population. Second, IQ gains should be most pronounced in the lower half of the IQ bell curve since this is the section of the population that prior to the education would have obtained relatively lower scores due to their inability to comprehend the intelligence test's instructions. With increased literacy, you should expect to see a change in the skewness of the IQ distribution from positive to negative as a result of higher rates of literacy in the lower half of the IQ distribution (but very little change in the top half of the distribution). You should also expect to see differences on the particular intelligence test subscales, with increased literacy showing the strongest effects on verbal tests of intelligence and minimal differences on other tests of intelligence. If all these predictions hold up, there would be support for the notion that secular IQ gains and race differences are not different phenomena but have a common origin in literacy.

To test these predictions, Marks looked at samples representative of whole populations (rather than individuals), and used ecological methods to calculate statistical associations between IQ and literacy rates across different countries. Were Marks' findings consistent with the predictions?