Brink Lindsey argues against using IQ scores as a metric of innate ability:
Though the tests are good measures of skills relevant to success in American society, the scores are only a good indicator of relative intellectual ability for people who have been exposed to equivalent opportunities for developing those skills – and who actually have the motivation to try hard on the test. IQ tests are good measures of innate intelligence–if all other factors are held steady. But if IQ tests are being used to compare individuals of wildly different backgrounds, then the variable of innate intelligence is not being tested in isolation. Instead, the scores will reflect some impossible-to-sort-out combination of ability and differences in opportunities and motivations. Let’s take a look at why that might be the case.
Comparisons of IQ scores across ethnic groups, cultures, countries, or time periods founder on this basic problem: The cognitive skills that IQ tests assess are not used or valued to the same extent in all times and places. Indeed, the widespread usefulness of these skills is emphatically not the norm in human history. After all, IQ tests put great stress on reading ability and vocabulary, yet writing was invented only about 6,000 years ago – rather late in the day given that anatomically modern humans have been around for over 100,000 years. And as recently as two hundred years ago, only about 15 percent of people could read or write at all.
More generally, IQ tests reward the possession of abstract theoretical knowledge and a facility for formal analytical rigor. But for most people throughout history, intelligence would have taken the form of concrete practical knowledge of the resources and dangers present in the local environment. To grasp how culturally contingent our current conception of intelligence is, just imagine how well you might do on an IQ test devised by Amazonian hunter-gatherers or medieval European peasants.
The mass development of highly abstract thinking skills represents a cultural adaptation to the mind-boggling complexity of modern technological society. But the complexity of contemporary life is not evenly distributed, and neither is the demand for written language fluency or analytical dexterity. Such skills are used more intensively in the most advanced economies than they are in the rest of the world. And within advanced societies, they are put to much greater use by the managers and professionals of the socioeconomic elite than by everybody else. As a result, American kids generally will have better opportunities to develop these skills than kids in, say, Mexico or Guatemala. And in America, the children of college-educated parents will have much better opportunities than working-class kids. [Emphasis added]
Recently, Greg Clark, author of A Farewell to Alms, has been pursuing a crazily ambitious research agenda on social mobility over long historical periods. He has been drawing on surname analysis to gauge the extent to which descendants of the upper classes of the 17th, 18th, and 19th centuries predominate in the upper classes of the present. His initial results are, frankly, rather discomfiting, as they at least suggest that — to grossly oversimplify matters — having literate ancestors two hundred years ago, when, as Brink observes, only 15 percent of people were literate, is associated with doing well in the 21st century. Viewed through this lens, the really interesting thing about the contemporary U.S. economy is not the persistence of inequality across groups, some of which were disproportionately literate two centuries ago while others were decidedly not, but rather the extent of the progress we’ve made in redressing these inequalities. Back in 2011, the libertarian economist Jason Sorens compared inequality in the U.S. to other New World post-slavery societies:
The U.S. has the least inequality, by a fair margin, of these countries. Of course, the U.S. also has a smaller combined percentage of blacks and Amerindians than all of these other countries except Costa Rica, Chile, Argentina, and Uruguay. But that’s precisely the point – the overriding factor determining inequality in New World countries is the white or mestizo percentage of the population. When you control for that, the U.S. actually has very low inequality.
If the U.S. is exceptional at all, it is exceptional for its high GDP per capita and low income inequality, relative to similarly situated countries.
There is, to be sure, another view, which is that a history of exclusion and disadvantage has absolutely no consequences in the present day and that Clark et al. are entirely wrong. This would mean that the children of less-skilled immigrants won’t require more substantial taxpayer-funded human capital investments than the children of educated middle-income native-born Americans to fare well as adults. Though I’m sure that this is true of some of the children of less-skilled immigrants, I wouldn’t count on it being true for all of them.