A crucial agent in our limiting definition of intelligence, which has a dark heritage in nineteenth-century biometrics and eugenics, was the British psychologist and statistician Charles Spearman, who became interested in the strong correlation between an individual’s high performance on tests assessing very different mental abilities. He surmised that human intelligence is a function not of specific knowledge but of the individual’s ability to manipulate abstract knowledge across a variety of domains. Spearman called this ability “general intelligence,” shorthanded g.
[…]“Recognizing that this measurement varied with age during childhood development, [Stanford psychologist Lewis] Terman advocated a new metric to quantify age-specific intelligence. If a subject’s “mental age” was the same as his or her physical age, their “intelligence quotient,” or IQ, was defined as exactly 100. If a subject lagged in mental age compared to physical age, the IQ was less than a hundred; if she was more mentally advanced, she was assigned an IQ above 100.”
[…]Because categories, measurements, and labels help us navigate the world and, in Umberto Eco’s undying words, “make infinity comprehensible,” IQ metrics enchanted the popular imagination with the convenient illusion of neat categorization. Like any fad that offers a shortcut for something difficult to achieve, they spread like wildfire across the societal landscape.
[…]“General intelligence (g) originated as a statistical correlation between tests given under particular circumstances to particular individuals. It morphed into the notion of “general intelligence” because of a hypothesis concerning the nature of human knowledge acquisition. And it was codified into “IQ” to serve the particular exigencies of war. In a cultural sense, the definition of g was an exquisitely self-reinforcing phenomenon: those who possessed it, anointed as “intelligent” and given the arbitration of the quality, had every incentive in the world to propagate its definition.”
[…]“As the civil rights movement and feminism highlighted chronic political and social inequalities in America, it became evident that biological and psychological features were not just inborn but likely to be deeply influenced by context and environment. The dogma of a single form of intelligence was also challenged by scientific evidence.”
Along came social scientists like Howard Gardner, whose germinal 1983 Theory of Multiple Intelligences set out to upend the tyranny of “selfish g” by demonstrating that human acumen exists along varied dimensions, subtler and more context-specific, not necessarily correlated with one another — those who score high on logical/mathematical intelligence, for instance, may not score high on bodily/kinesthetic intelligence, and vice versa.
Mukherjee considers the layered implications for g and its active agents:
“Is g heritable? In a certain sense, yes. In the 1950s, a series of reports suggested a strong genetic component. Of these, twin studies were the most definitive. When identical twins who had been reared together — i.e., with shared genes and shared environments — were tested in the early fifties, psychologists had found a striking degree of concordance in their IQs, with a correlation value of 0.86. In the late eighties, when identical twins who were separated at birth and reared separately were tested, the correlation fell to 0.74 — still a striking number.
But the heritability of a trait, no matter how strong, may be the result of multiple genes, each exerting a relatively minor effect. If that was the case, identical twins would show strong correlations in g, but parents and children would be far less concordant. IQ followed this pattern. The correlation between parents and children living together, for instance, fell to 0.42. With parents and children living apart, the correlation collapsed to 0.22. Whatever the IQ test was measuring, it was a heritable factor, but one also influenced by many genes and possibly strongly modified by environment — part nature and part nurture.
The most logical conclusion from these facts is that while some combination of genes and environments can strongly influence g, this combination will rarely be passed, intact, from parents to their children. Mendel’s laws virtually guarantee that the particular permutation of genes will scatter apart in every generation. And environmental interactions are so difficult to capture and predict that they cannot be reproduced over time. Intelligence, in short, is heritable (i.e., influenced by genes), but not easily inheritable (i.e., moved down intact from one generation to the next).”
[…]In the 1980s, scientists conducted numerous studies demonstrating a discrepancy in IQ across the races, with white children scoring higher than their black peers. While the controversial results initially provided rampant fodder for racists, they also provided incentive for scientists to do what scientists must — question the validity of their own methods. In a testament to trailblazing philosopher Susanne Langer’s assertion that the way we frame our questions shapes our answers, it soon became clear that these IQ tests weren’t measuring the mythic g but, rather, reflected the effects of contextual circumstances like poverty, illness, hunger, and educational opportunity. Mukherjee explains:
“It is easy to demonstrate an analogous effect in a lab: If you raise two plant strains — one tall and one short — in undernourished circumstances, then both plants grow short regardless of intrinsic genetic drive. In contrast, when nutrients are no longer limiting, the tall plant grows to its full height. Whether genes or environment — nature or nurture — dominates in influence depends on context. When environments are constraining, they exert a disproportionate influence. When the constraints are removed, genes become ascendant.
[…]If the history of medical genetics teaches us one lesson, it is to be wary of precisely such slips between biology and culture. Humans, we now know, are largely similar in genetic terms — but with enough variation within us to represent true diversity. Or, perhaps more accurately, we are culturally or biologically inclined to magnify variations, even if they are minor in the larger scheme of the genome. Tests that are explicitly designed to capture variances in abilities will likely capture variances in abilities — and these variations may well track along racial lines. But to call the score in such a test “intelligence,” especially when the score is uniquely sensitive to the configuration of the test, is to insult the very quality it sets out to measure.
Genes cannot tell us how to categorize or comprehend human diversity; environments can, cultures can, geographies can, histories can. Our language sputters in its attempt to capture this slip. When a genetic variation is statistically the most common, we call it normal — a word that implies not just superior statistical representation but qualitative or even moral superiority… When the variation is rare, it is termed a mutant — a word that implies not just statistical uncommonness, but qualitative inferiority, or even moral repugnance.
And so it goes, interposing linguistic discrimination on genetic variation, mixing biology and desire.”
[…] […]it is to identity that Mukherjee points as an object of inquiry far apter than intelligence in understanding personhood. In a passage emblematic of the elegance with which he fuses science, cultural history, and lyrical prose, Mukherjee writes:“Like the English novel, or the face, say, the human genome can be lumped or split in a million different ways. But whether to split or lump, to categorize or synthesize, is a choice. When a distinct, heritable biological feature, such as a genetic illness (e.g., sickle-cell anemia), is the ascendant concern, then examining the genome to identify the locus of that feature makes absolute sense. The narrower the definition of the heritable feature or the trait, the more likely we will find a genetic locus for that trait, and the more likely that the trait will segregate within some human subpopulation […] Conversely, the more we widen the definition of a feature or trait (say, intelligence, or temperament), the less likely that the trait will correlate with single genes — and, by extension, with races, tribes, or subpopulations. […] The narrowness, or breadth, of the definition of a feature is, in fact, a question of identity — i.e., how we define, categorize, and understand humans (ourselves) in a cultural, social, and political sense. The crucial missing element in our blurred conversation on the definition of race, then, is a conversation on the definition of identity.”
Source: The Marginalian (Brain Pickings) (November 30, 2016)
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