In 1969, in my junior year at the University of Dallas, Arthur Jensen published a long article in the Harvard Educational Review--"How Much Can We Boost IQ and Scholastic Achievement?" He answered his question in the first sentence: "Compensatory education has been tried, and it apparently has failed." In the United States and elsewhere, children from lower class families were not as successful on average as children from higher class families. The lower class children seemed to be less intelligent on average, as measured by their low scores on IQ tests. Since it was commonly assumed that human intelligence, like most other human capabilities, was shaped mostly, if not entirely, by the social environment, public policy makers believed that if lower class children were given advanced educational opportunities at an early age (such as the Head Start program in the U.S.), this would raise their intelligence so that they would show the same scholastic achievement as the upper class children. Jensen's survey of the evidence that this had failed, and that the failure was due to genetically innate differences in intelligence that could not be easily changed by environmental factors, provoked outrage: he was denounced as a racist and a fascist. His teaching and his lectures were disrupted by violent protests, and many people demanded that he be fired from his job at the University of California-Berkeley. Jensen had provoked this anger because he had challenged the egalitarian claim of left liberalism that human beings are born with equal capacities that can be cultivated in any direction by the social environment of their early childhood.
In September of 1971, when I was beginning my graduate work at the University of Chicago, Richard Herrnstein published an article in The Atlantic entitled "I.Q." Two years later, he expanded his article into a book--I.Q. in the Meritocracy. Like Jensen, he argued that while general intelligence (g) as measured by IQ tests was shaped by both genes and environment, the variation in intelligence was due mostly to genes--perhaps as much as 80%. Moreover, he claimed that in modern liberal societies, which strive to remove the social and legal obstacles to social mobility, actual social mobility would be blocked by the innate human differences in intelligence. When people are free to rise and fall by their own merit, they will sort themselves out according to their innate differences. So societies that increase equality of opportunity for everyone will inevitably produce an unequal class structure where the smartest people will be the ruling class.
This tendency to meritocracy with a cognitive elite is strengthened by the growing complexity of modern societies in which the most highly paid and prestigious occupations require people who can handle cognitively challenging tasks, so that high IQ is correlated with economic success. Thus, the class structure in an open liberal society will be built on natural human inequalities.
Herrnstein put his argument into the form of a syllogism:
1. If differences in mental abilities are inherited, and
2. If success requires those abilities, and
3. If earnings and prestige depend on success,
4. Then social standing (which reflects earnings and prestige) will be based to some extent on inherited differences among people (I.Q. in the Meritocracy, 198-199).
Herrnstein thought this had profound implications for political philosophy, because it refuted "the egalitarian society of our philosophical heritage" (221), a heritage that included not only Marxism but also the Declaration of Independence. Both the Communist Manifesto and the Declaration of Independence had affirmed the "vision of a classless society," but Herrnstein seemed to show that we were not moving to a classless society. If he was right, then the arbitrary barriers to social mobility in a traditional aristocracy will be replaced by the biological barriers to social mobility in a modern meritocracy.
This bothered me because I was not willing to give up on the Lockean liberal principle of equal liberty as expressed in the Declaration of Independence. I wondered whether there could be a Darwinian defense of this principle.
But while I was open to Herrnstein's reasoning, it seemed that most people in the academic world were not. Like Jensen, he was subjected to angry persecution. As a result of this, the scientific study of intelligence became a taboo subject. Only a few people continued this research, and it was often hard for them to find the necessary funding.
Then, in 1994, the controversy was reignited by the publication of The Bell Curve: Intelligence and Class Structure in American Life, coauthored by Herrnstein and Charles Murray. Herrnstein died before the publication of the book, so Murray was left to face the vitriolic attacks that it elicited. As usual, he was denounced as a racist and a fascist.
The mob violence against Murray last year at Middlebury College shows that the Darwinian science of intelligence is still taboo for many professors and students. And yet, it seems to me that in general the angry resistance is not as great as it once was, because the research on the genetic basis of intelligence has become so impressive that it has to be taken seriously.
Perhaps the best recent survey of that research is Richard Haier's The Neuroscience of Intelligence (Cambridge University Press), published last year. Haier shows the overwhelming evidence that has accumulated over 40 years supporting the genetic basis of intelligence. He stresses the most impressive evidence coming from neuroimaging that now allows us to see how IQ scores are correlated with the structure and functioning of the brain, which has been Haier's area of research.
He shows how the correlations among mental tests point to the existence of an underlying general factor of intelligence that is called g. People who do well on one test tend to do well on other tests. This holds for tests of reasoning, spatial ability, memory, processing speed, and vocabulary.
He also shows that these tests have great predictive validity. High IQ scores at an early age predict educational achievement, professional success, income, and healthy aging. He also emphasizes the importance of general intelligence for everyday life. The complexity of everyday life is challenging, and people with low IQs are less successful in managing the challenges of life. For example, we can compare low and high IQ groups--the low having IQs of 75-90, the high having IQs of 110-125. People in the low group are 133 times more likely to drop out of high school, 10 times more likely to be a chronic welfare recipient, 7.5 times more likely to be incarcerated, 6.2 times more likely to live in poverty, and 3 times more likely to die in a traffic accident. People who are not smart have a hard time navigating their way through the complex cognitive challenges of everyday life. It really is better to be smart.
The twin and adoption studies of intelligence consistently show that genes cannot account for 100% of the variance. So there are environmental factors involved. But then the problem is estimating the relative contributions of genes and environment. Different studies give different proportions, with the most common view being about 50-50. The explanation for these different outcomes might be the age at which the twins are tested, because the heritability of IQ in identical twins increases with age--from about 30% at age 5 to over 80% starting at age 18. So for young children environmental factors explain most of the variance, while for older children genes explain most of the variance. That's why enhanced educational programs for young lower class children do sometimes raise their IQ scores for a few years, but then this improvement disappears as they grow older.
That such IQ differences are rooted in our evolutionary history is indicated by the fact that other mammalian animals also show IQ differences. Studies of genetically diverse mice learning various kinds of tasks show a g-factor intelligence. Mice show a bell curve of individual differences, so that some mice are innately smarter than others as shown in their diverse learning abilities (Matzel et al., 2003, 2013). Similarly, chimpanzees show individual variability in heritable intelligence (Hopkins et al., 2014). We might explain this through the "social brain" hypothesis: for animals that live in complex societies, there is an evolutionary pressure favoring the cognitive ability to navigate through a complex social world.
But the most impressive recent evidence confirming the evolved biological nature of intelligence comes from improvements in the technology of neuroimaging that allow us to see the structural and functional patterns in individual human brains that are correlated with intelligence.
For centuries, scientists have tried to correlate brain size and intelligence, with the thought that bigger brains allow higher intelligence. Now we know from many MRI studies, that there is indeed a correlation between brain size and intelligence test scores, although the correlation is modest--average correlations ranging from .22 to .40 (McDaniel, 2005).
Another general conclusion from neuroimaging studies is that all brains do not work in the same way. Every individual brain is different, and the patterns differ according to age and sex. Young brains operate differently from old brains. And male brains operate differently from female brains. There are differences in the density and organization of the white matter fibers that connect the areas of the brain. There are also differences in amount of gray matter (the clusters of neurons) in different areas of the brain.
Amazingly, these individual differences are so distinctive that fMRI imaging can identify the unique pattern of connectivity among brain areas n an individual brain as a kind of brain fingerprint. And these brain fingerprints can predict intelligence (Finn et al., 2015).
Neuroimaging has also supported the general conclusion that intelligence is not concentrated in one part of the brain, such as the frontal lobes. Rather, intelligence is correlated with a distributed network of different areas of the brain. Haier has concluded that the brain areas connected with intelligence are mostly concentrated in the parietal and frontal areas, which are areas associated with memory, attention, and language. So he has defended a "Parietal-Frontal Integration Theory" of intelligence (Jung and Haier 2007).
Haier concludes that all of this research supports Herrnstein's original claim in 1971: a liberal society that removes the legal and political obstacles to social mobility will allow the biological differences in intelligence among individuals to be expressed in a class structure of meritocracy based on innate intelligence with a cognitive elite at the top.
Against this conclusion is all of the research that apparently shows that it's not genes but social-economic status (SES) that determines social success or failure. The children of parents with high SES tend to be more successful than the children of parents with low SES. The flaw in this research, however, Haier argues, is that it ignores how SES is confounded with intelligence, because SES has a strong genetic component (Lubinski, 2009; Trzaskowski et al., 2014).
To explain this point, Haier asks us to consider two alternative trains of thought. The common train of thought about the importance of SES goes this way:
"Higher income allows upward mobility, especially the ability to move from poor environments to better ones. Better neighborhoods typically include better schools and more resources to foster children's development so that children now have many advantages. If the children have high intelligence and greater academic and economic success, it could be concluded that higher SES was the key factor driving this chain of events."An alternative train of thought favored by Haier and Herrnstein goes this way:
"Generally, people with higher intelligence get jobs that require more of the g-factor, and these jobs tend to pay more money. There are many factors involved, but empirical research shows g is the single strongest predictive factor for obtaining high-paying jobs that require complex thinking. Higher income allows upward mobility, especially the ability to move from poor environments to better ones. This often includes better schools and more resources to foster children's development so that children now have many advantages. If the children have high intelligence and greater academic and economic success, it could be concluded that higher parental intelligence was the key factor driving this chain of events due in large part to the strong genetic influences on intelligence" (192).This second scenario is strengthened by the fact of assortative mating. Over the past 60 years, very intelligent women have been able to move into high levels of advanced education and professional training--opportunities denied to women in the past. As one result of this, many highly intelligent men and women meet in colleges and universities and marry, and then they pass on their high IQ genes to their children. They also become "power couples" with high double-income wealth. This is exactly the sorting out of people based on intelligence that Herrnstein foresaw.
The point here is that yes, of course, SES is an important factor in determining social and economic success; but SES includes a genetic component of innate intelligence.
This leads Haier to some disturbing conclusions that he identifies as "neuro-poverty" and "neuro-social-economic status." Living in poverty is to some significant degree rooted in the neurobiology of low intelligence that is beyond anyone's control. Similarly, living in the highest social and economic classes is to some significant degree rooted in the neurobiology of high intelligence that is beyond anyone's control.
There is one optimistic possibility, however. Even though the neurobiology of intelligence is today "beyond anyone's control," because so far there is no proven scientific treatment for enhancing innate intelligence, Haier does foresee that sometime in the future, scientists might find ways to enhance intelligence through genetic engineering, drug therapy, or neuromicrochips.
But until that happens, we are left with the disturbing conclusion that many people lack the innate intelligence to be very successful in life through no fault of their own. Some people do better than others in the natural genetic lottery, which is not based on merit.
So does this deny the principle of equal liberty in the Declaration of Independence? How can people have equal rights to life, liberty, and the pursuit of happiness if in fact their place in the social class system depends to a large extent on their genetically inherited cognitive abilities?
In 1981, I took up this problem in the first conference paper that I wrote on Darwinian political theory. It was entitled "Charles Darwin and the Declaration of Independence," and it was presented at the national convention of the American Political Science Association in Denver. In 1984, a revised version of this paper was published as "Darwin, Aristotle, and the Biology of Human Rights" in Social Science Information (vol. 23, no. 3).
I argued that Darwinian biology can recognize that the equality of all human beings as possessing a common human nature is fully consistent with the inequality of human beings due to their different natural endowments. The reality of biological species is such that members of the same species share a common nature despite their individual differences. This is the modern biological justification for the Lockean claim that although human beings are naturally unequal in many respects, they are equal in certain rights by virtue of their human propensity to assert their right to pursue their interests in life.
The equality of rights in the Declaration of Independence is an equality of opportunity but not an equality of results. Herrnstein was wrong to suggest that Jefferson wanted a classless society. As Jefferson indicated, he was hope for a "natural aristocracy" of "virtue and talents" rather than an "artificial aristocracy" of "wealth and birth." As Murray indicated in the last chapter of The Bell Curve ("A Place for Everyone"), this Jeffersonian "natural aristocracy" looks a lot like what he and Herrnstein see as a meritocracy.
I elaborated this last point in some of my previous posts on Murray, IQ, and human biodiversity here, here, here, here, here, here, here, here, here, here, here, here, here, here.
Arnhart, Larry. 1984. "Darwin, Aristotle, and the Biology of Human Rights." Social Science Information 23: 493-521.
Finn, E. S., Shen, X., Scheinost, D., Rosenberg, M. D., Huang, J., Chun, M. M., Papademetris, X., & Constable, R. T. 2015. "Functional Connectome Fingerprinting: Identifying Individuals Using Patterns of Brain Connectivity." Nature Neuroscience 18: 1664-1671.
Haier, Richard J. 2017. The Neuroscience of Intelligence. New York: Cambridge University Press.
Herrnstein, Richard J. 1971. "I.Q." The Atlantic, September.
Herrnstein, Richard J. 1973. I.Q. in the Meritocracy. Boston: Little, Brown, and Company.
Hopkins, W. D., Russe, J. L., & Schaeffer, J. 2014. "Chimpanzee Intelligence Is Heritable." Current Biology 24: 1649-1652.
Jensen, Arthur R. 1969. "How Much Can We Boost IQ and Scholastic Achievement." Harvard Educational Review 39: 1-123.
Jung, R. E., & Haier, R. J. 2007. "The Parietal-Frontal Integration Theory (P-FIT) of Intelligence: Converging Neuroimaging Evidence." Behavioral and Brain Sciences 30: 135-54.
Lubinski, D. 2009. "Cognitive Epidemiology: With Emphasis on Untangling Cognitive Ability and Socioeconomic Status." Intelligence 37: 625-33.
Matzel, L. D., Han, Y. R., Grossman, H., Karnik, M. S., Patel, D., Scott, N., Specht, S. M., & Gandhi, C. C. 2003. "Individual Differences in the Expression of a 'General' Leaning Ability in Mice." Journal of Neuroscience 23: 6423-6433.
Matzel, L. D., Sauce, B., & Wass, C. 2013. "The Architecture of Intelligence: Converging Evidence from Studies of Humans and Animals." Current Directions in Psychological Science 22: 342-348.
McDaniel, M. A. 2005. "Big-Brained People Are Smarter: A Meta-Analysis of the Relationship Between In Vivo Brain Volume and Intelligence." Intelligence 33: 337-346.
Trzaskowski, M., Harlaar, N., Arden, R., Krapohl, E., Rimfeld, K., McMillan, A., Dale, P. S., & Plomin, R. 2014. "Genetic Influence on Family Socioeconomic Status and Children's Intelligence." Intelligence 42: 83-88.