What exactly is the relationship between IQ scores and wealth? Individuals with high IQ scores tend to be wealthier than those with lower IQ scores. Similarly, nations with higher average IQ scores tend to be wealthier than those nations with lower average IQ scores. A few years ago, Richard Lynn (a psychologist at the University of Ulster) and Tatu Vanhanen (a political scientist at the University of Tampere in Finland) published two books surveying the correlation between IQ and wealth around the world. They estimated that the average IQ for East Asian nations was 105, for Europeans 99, and for sub-Saharan Africa 67. They argued that the high correlation between average IQ of a nation and its wealth showed that the cause of the gap between the rich and poor countries was genetic rather than environmental, and therefore that this gap was unlikely to be closed anytime soon.
In A Troublesome Inheritance, Nicholas Wade points out the fundamental defect in their argument (189-93). Their own data suggested that as a nation becomes wealthier, IQ scores can increase 10 or more points in one generation. So, for example, the average IQ score for West German children was 99 in 1967 and 107 in 1984. For East German children, there was a rise from 90 to 99. The cause of these changes cannot be genetic. It must be environmental. As a nation becomes wealthier, its citizens can do better on IQ tests.
Although he does not explicitly identify it as such, Wade is pointing to the "Flynn effect," named after political scientist James Flynn who has written most about it. Over the past century, IQ tests have shown massive gains of 30 to 50 points. Flynn calculates that in 1917, Americans had a mean IQ of 72 (against today's norms); and he estimates that it was 67 in 1900.
So while many developing nations today have a lower mean IQ than that of the U.S. today, the mean IQ today for developing nations is not as low for most of them as it was for the U.S. in 1900. As the environmental changes that brought higher IQ scores to the U.S. and other developed nations spread to the developing nations, we could see some closing of the gap between the rich and the poor nations. To say that developing nations that today have low IQs lack the intelligence to industrialize is false, because the U.S. and other nations had similarly low IQs in 1900, and yet they industrialized.
In fact, the evidence indicates that IQ scores have been increasing in the developing nations. For example, scores on some tests in Kenya have increased by 13.85 points over 14 years, a rate of gain of almost 1 point per year. Since 1990, the Scandinavian countries have not shown increasing IQ scores. If this slowing in IQ gains were to occur in the rest of the developed world, the developing world could eventually catch up and even overtake the developed world.
Flynn has shown that scored against the American whites of 1947-48, the American blacks of 2002 had a mean IQ of 104.31. This does not prove that the black/white IQ gap has a purely environmental cause. But it does show that an environmental cause is possible.
Moreover, one should keep in mind what Flynn and Steven Pinker have identified as the "moral Flynn effect." As people get smarter, they can use their cognitive ability for abstraction and logic to improve their moral reasoning, which leads to less violence.
A good summary of Flynn's research is his Are We Getting Smarter?--Rising IQ in the Twenty-First Century (Cambridge University Press, 2012).
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