From what people tell me IQ is a social construct which is totally controlled by environmental variables, and so is not of much interest. But curiously the other day when I looked at the hits on this website over the past 3+ years a huge number of highly accessed posts had to do with intelligence and IQ. In any case, seeing as how many readers of this weblog are having, or going to have, children at a relatively advanced age (in an evolutionary sense) I thought this post would be a good public service announcement. Below is a figure from a preprint posted on arXiv, The effect of paternal age on offspring intelligence and personality when controlling for paternal trait level (via Haldane’s Sieve):
Modern evolutionary genetics owes its origins to a series of intellectual debates around the turn of the 20th century. Much of this is outlined in Will Provines’ The Origins of Theoretical Population Genetics, though a biography of Francis Galton will do just as well. In short what happened is that during this period there were conflicts between the heirs of Charles Darwin as to the nature of inheritance (an issue Darwin left muddled from what I can tell). On the one side you had a young coterie around William Bateson, the champion of Gregor Mendel’s ideas about discrete and particulate inheritance via the abstraction of genes. Arrayed against them were the acolytes of Charles Darwin’s cousin Francis Galton, led by the mathematician Karl Pearson, and the biologist Walter Weldon. This school of “biometricians” focused on continuous characteristics and Darwinian gradualism, and are arguably the forerunners of quantitative genetics. There is some irony in their espousal of a “Galtonian” view, because Galton was himself not without sympathy for a discrete model of inheritance!
In the end science and truth won out. Young scholars trained in the biometric tradition repeatedly defected to the Mendelian camp (e.g. Charles Davenport). Eventually, R. A. Fisher, one of the founders of modern statistics and evolutionary biology, merged both traditions in his seminal paper The Correlation between Relatives on the Supposition of Mendelian Inheritance. The intuition for why Mendelism does not undermine classical Darwinian theory is simple (granted, some of the original Mendelians did seem to believe that it was a violation!). Many discrete genes of moderate to small effect upon a trait can produce a continuous distribution via the central limit theorem. In fact classical genetic methods often had difficulty perceiving traits with more than half dozen significant loci as anything but quantitative and continuous (consider pigmentation, which we know through genomic methods to vary across populations mostly due to half a dozen segregating genes or so).
Prompted by my post Ta-Nehisi Coates reached out to Neil Risch for clarification on the nature (or lack thereof) of human races. All for the good. The interview is wide ranging, and I recommend you check it out. Read the comments too! Very enlightening (take that however you want).
When it comes to this debate I have focused on the issue of population substructure, or race. The reason is simple. Due to Lewontin’s Fallacy it is widely understood among the “well informed general public” that “biology has disproved race.” Actually, this is a disputable assertion. For a non-crank evolutionary biologist who is willing to defend the race concept for humans, see Jerry Coyne. When you move away from the term “race,” then you obtain even more support from biologists for the proposition that population structure matters. For example, a paper in PLoS GENETICS which came out last week: Analysis of the Genetic Basis of Disease in the Context of Worldwide Human Relationships and Migration. In other words, it is useful to understand the genetic relationships of populations, and individual population identity, because traits correlate with population history. Barring total omniscience population history will always probably matter to some extent, because population history influences suites of traits. If nothing in evolutionary biology makes sense except in light of phylogeny, much of human biology is illuminated by phylogeny.
But that doesn’t speak to the real third rail, intelligence. Very few people are offended by the idea of the correlation between lactase persistence and particular populations. Neil Risch says in the interview with Coates:
As an aside in a fascinating City Journal piece on educational policy, A Wealth of Words:
Vocabulary doesn’t just help children do well on verbal exams. Studies have solidly established the correlation between vocabulary and real-world ability. Many of these studies examine the Armed Forces Qualification Test (AFQT), which the military devised in 1950 as an entrance requirement and a job-allocating device. The exam consists of two verbal sections (on vocabulary size and paragraph comprehension) and two math sections. The military has determined that the test predicts real-world job performance most accurately when you double the verbal score and add it to the math score. Once you perform that adjustment, according to a 1999 study by Christopher Winship and Sanders Korenman, a gain of one standard deviation on the AFQT raises one’s annual income by nearly $10,000 (in 2012 dollars). Other studies show that much of the disparity in the black-white wage gap disappears when you take AFQT scores—again, weighted toward the verbal side—into account.
A paper on the psychology of religious belief, Paranormal and Religious Believers Are More Prone to Illusory Face Perception than Skeptics and Non-believers, came onto my radar recently. I used to talk a lot about the theory of religious cognitive psychology years ago, but the interest kind of faded when it seemed that empirical results were relatively thin in relation to the system building (Ara Norenzayan’s work being an exception to this generality). The theory is rather straightforward: religious belief is a naturally evoked consequence of the general architecture of our minds. For example, gods are simply extensions of persons, and make natural sense in light of our tendency to anthromorphize the world around us (this may have had evolutionary benefit, in that false positives for detection of other agents was far less costly than false negatives; think an ambush by a rival clan).*
There are many things that a given individual believes which are ‘heterodox’ in their social circle. For example, I have long thought that intelligence tests are predictive of life outcomes, and somewhat heritable in a genetic sense (these are both true, the objection of skeptics usually rests on the fact that they are skeptical of the construct itself). As I have explained here before I did not always hold to these views. Rather, when I was in seventh grade a teacher who mentored me somewhat took me aside after class, and suggested that perhaps some of my slower classmates were not quite as lazy as I obviously presumed (I tended to get impatient during mandatory group projects). When I was 5 years old and starting kindergarten my command of English was rather weak, and my mother explained to me that Americans were a very smart people. By the end of the year I was excelling. Throughout my elementary school years I frankly had a smugness about me, because I accepted what my parents told me, that academic outcome is a function of the virtue of effort. And I had quite a bit of virtue if the results were any gauge.
But as I said, it is the fashion today to reject I.Q. Usually people put intelligence in air quotes. The converse of intelligence, stupidity, is also not well acknowledged. Just as I took my realized intelligence to be a mark of my virtue (false, my virtue and moral compass are distinct, and perhaps even at some cross-purposes, with my analytic powers), I perceived stupidity as evidence of sloth and low moral character. This is just not so.
I.Q. is probably a hot-potato topic because of its associations with realized group differences, mostly race, but to some extent class. I think that the phenomenon is real and important, but that may not matter. I’ve been sobered by the realization recently that Soviet Communism persisted for 70 years. I don’t bring this example up to analogize skepticism of I.Q. with Communism, but to illustrate even patently grotesque and false views can persist for decades beyond their “sell-by” date. And yet sometimes it turns out that I’m not the only person out there who thinks that some people are smart, and some people are stupid. Here’s Felix Salmon, Who is speaking for the poor?:
In light of the previous post I was curious about the literature on inbreeding depression of IQ. A literature search led me to conclude two things:
- This is not a sexy field. A lot of the results are old.
- The range in depression for first cousin marriages seems to be on the order of 2.5 to 10 IQ points. In other words ~0.15 to ~0.65 standard deviation units of decline in intelligence.
The most extreme case was this paper from 1993, Inbreeding depression and intelligence quotient among north Indian children. The authors compared the children of first cousin marriages, and non-bred in individuals, from a sample of Muslims in Uttar Pradesh of comparable socioeconomic status (though the authors note that inbreeding has a positive correlation with socioeconomic status in this community). A table with results speaks for itself:
One point which I’ve made on this weblog several times is that on a whole range of issues and behaviors people simply follow the consensus of their self-identified group. This group conformity probably has deep evolutionary origins. It is often much cognitively “cheaper” to simply utilize a heuristic “do what my peers do” than reason from first principles. The “wisdom of the crowds” and “irrational herds” both arise from this dynamic, positive and negative manifestations. The interesting point is that from a proximate (game-theoretic rational actor) and ultimate (evolutionary fitness) perspective ditching reason is often quite reasonable (in fact, it may be the only feasible option if you want to “understand,” for example, celestial mechanics).
There’s a new paper in PLoS ONE, The Distance Between Mars and Venus: Measuring Global Sex Differences in Personality*, which suggests that by measuring variation of single observed personality traits researchers are missing larger underlying patterns of difference. The Distance Between Mars and Venus: Measuring Global Sex Differences in Personality:
In conclusion, we believe we made it clear that the true extent of sex differences in human personality has been consistently underestimated. While our current estimate represents a substantial improvement on the existing literature, we urge researchers to replicate this type of analysis with other datasets and different personality measures. An especially critical task will be to compare self-reported personality with observer ratings and other, more objective evaluation methods. Of course, the methodological guidelines presented in this paper can and should be applied to domains of individual differences other than personality, including vocational interests, cognitive abilities, creativity, and so forth. Moreover, the pattern of global sex differences in these domains may help elucidate the meaning and generality of the broad dimension of individual differences known as “masculinity-femininity”…In this way, it will be possible to build a solid foundation for the scientific study of psychological sex differences and their biological and cultural origins.
Several readers have pointed me to this amusing story, Court OKs Barring High IQs for Cops:
A man whose bid to become a police officer was rejected after he scored too high on an intelligence test has lost an appeal in his federal lawsuit against the city.
“This kind of puts an official face on discrimination in America against people of a certain class,” Jordan said today from his Waterford home. “I maintain you have no more control over your basic intelligence than your eye color or your gender or anything else.”
Jordan, a 49-year-old college graduate, took the exam in 1996 and scored 33 points, the equivalent of an IQ of 125. But New London police interviewed only candidates who scored 20 to 27, on the theory that those who scored too high could get bored with police work and leave soon after undergoing costly training.
The average score nationally for police officers is 21 to 22, the equivalent of an IQ of 104, or just a little above average.
But the U.S. District Court found that New London had “shown a rational basis for the policy.” In a ruling dated Aug. 23, the 2nd Circuit agreed. The court said the policy might be unwise but was a rational way to reduce job turnover.
3. Is it true Feynman’s IQ score was only 125?
Feynman was universally regarded as one of the fastest thinking and most creative theorists in his generation. Yet it has been reported-including by Feynman himself-that he only obtained a score of 125 on a school IQ test. I suspect that this test emphasized verbal, as opposed to mathematical, ability. Feynman received the highest score in the country by a large margin on the notoriously difficult Putnam mathematics competition exam, although he joined the MIT team on short notice and did not prepare for the test. He also reportedly had the highest scores on record on the math/physics graduate admission exams at Princeton. It seems quite possible to me that Feynman’s cognitive abilities might have been a bit lopsided-his vocabulary and verbal ability were well above average, but perhaps not as great as his mathematical abilities. I recall looking at excerpts from a notebook Feynman kept while an undergraduate. While the notes covered very advanced topics for an undergraduate-including general relativity and the Dirac equation-it also contained a number of misspellings and grammatical errors. I doubt Feynman cared very much about such things.
Amy Harmon has a very long piece in The New York Times, Navigating Love and Autism. It’s about a couple who both have been diagnosed with Asperger syndrome. Like cancer I suspect that this term brackets a lot of different issues into one catchall label, not to mention the acknowledgment that it’s a spectrum. When I spent time with the Bay Area Less Wrong community I would observe the range in tendencies and neurological diversity of people who clearly would be classified as “high functioning autistic” (to be clear, these were individuals strongly selected for high general intelligence, with a minimum threshold of around two standard deviations above the norm). The lack of comprehension of religiosity and bias toward libertarianism were two salient characteristics of this sect (though people who have met me don’t classify me as having Asperger syndrome, I have these two cognitive biases myself)
The title says it all, and I yanked it from a paper that is now online (and free). It’s of interest because of its relevance to the future genetic understanding of complex cognitive and behavioral traits. Here’s the abstract:
General intelligence (g) and virtually all other behavioral traits are heritable. Associations between g and specific single-nucleotide polymorphisms (SNPs) in several candidate genes involved in brain function have been reported. We sought to replicate published associations between 12 specific genetic variants and g using three independent, well-characterized, longitudinal datasets of 5571, 1759, and 2441 individuals. Of 32 independent tests across all three datasets, only one was nominally significant at the p ~ .05 level. By contrast, power analyses showed that we should have expected 10–15 significant associations, given reasonable assumptions for genotype effect sizes. As positive controls, we confirmed accepted genetic associations for Alzheimer disease and body mass index, and we used SNP-based relatedness calculations to replicate estimates that about half of the variance in g is accounted for by common genetic variation among individuals. We conclude that different approaches than candidate genes are needed in the molecular genetics of psychology and social science.
The New York Times has a short piece on Steven Pinker up. Nothing too new to long time followers of the man and his work. I would like to point readers to the fact that Steven Pinker has a F.A.Q. up for The Better Angels of Our Nature: Why Violence Has Declined. He links to my post, Relative angels and absolute demons, as supporting his dismissal of Elizabeth Kolbert’s review in The New Yorker. I have to admit that I find much, though not all, of the coverage of science in The New Yorker to exhibit some of the more annoying stereotypical caricatures of humanists when confronting the specter of natural philosophy.
I should also mention I started reading The Better Angels of Our Nature over Thanksgiving. I’m only ~20% through it, and probably won’t finish until Christmas season gets into high gear, but so far it’s a huge mess. In both a good way, and a bad way. The good way is that it’s incredibly rich in its bibliography, with fascinating facts strewn about the path of the narrative. The bad way is that so far it lacks the tightness of The Blank Slate or The Language Instinct in terms of argument. This may change. Finally, I think I should mention that Pinker has already addressed some of the criticisms of his methodologies brought up in the comments sections of my posts. Those who have specific critiques probably should read the book, because he seems to try sincerely to address those. Or at least they should address those critiques to people who have bothered to read the book.
I was warned off social psychology years ago by a friend (who was a research psychologist) because of the field’s propensity for ‘sexy’ results which get a lot of media play. As a lay person he doubted I could tell the fake from the reliable, the one off from the replicable. Later someone else told me about how dispiriting it was engaging in data dredging to find something publishable in a lab where they were working, even though many of the principals involved obviously assumed that the results weren’t robust. Keep that in mind when you read about the mind-boggling scientific fraud perpetrated by Diederik Stapel. It looks like he might be the Bernie Madoff of psychology. The Lehman Brothers to the Long Term Capital Management of Marc Hauser. Here’s a taste:
Stapel’s work encompassed a broad range of attention-catching topics, including the influence of power on moral thinking and the reaction of psychologists to a plagiarism scandal. The committee, which interviewed dozens of Stapel’s former students, postdoctoral researchers, co-authors, and colleagues, found that Stapel alone was responsible for the fraud. The panel reported that he would discuss in detail experimental designs, including drafting questionnaires, and would then claim to conduct the experiments at high schools and universities with which he had special arrangements. The experiments, however, never took place, the universities concluded. Stapel made up the data sets, which he then gave the student or collaborator for analysis, investigators allege. In other instances, the report says, he told colleagues that he had an old data set lying around that he hadn’t yet had a chance to analyze. When Stapel did conduct actual experiments, the committee found evidence that he manipulated the results.
Here’s the controversial thing I’m going to say: instances of flamboyant fraud are probably far less of an issue in a discipline like social psychology than more subtle biases and systematic incentives. Similarly, someone like Bernie Madoff was notable for the havoc he caused on an individual level, but he paled in the aggregate against the death by a thousand cuts that occurred as the housing market collapsed under the pall of modest “liar loans” and the like. And this isn’t just a problem with science. ‘Sexy’ social psychological research is routinely blasted by the press, and devoured by the public. Incentives matter, and Diederik Stapel is just the reductio ad absurdum of scientists who respond to the repeated 15 minutes of fame which the press provides. Most of the time it’s not so blatant, nor frankly so malicious in consequence. I doubt that there are many Diederik Stapel’s in the field, else he wouldn’t have gotten so far with bluster and bluff.
I saw this link posted on twitter, IQ and Human Intelligence:
An interesting finding from genetic research, which Mackintosh mentions, only in passing, as posing a problem in the estimation of the heritability of g, is that there is greater assortative mating for g than for any other behavioral trait; that is, spouse correlations are only ∼.1 for personality and only ∼.2 for height or weight, but the correlation for assortative mating for g is ∼.4. In addition to indicating that people are able to make judgments about g in real life, this finding suggests that assortative mating may contribute to the substantial additive genetic variance for g, because positive assortative mating for a character can increase its additive genetic variance.
I’ve seen these sort of results before. The review is from 1999. In general I always wonder if quantitative values for personality are not to be trusted because of issues with the measurement of personality types. But this is clearly not an issue with height or weight. And in the case of height the overwhelming causal explanation for variation in the West is genetic variation. Overall I’m rather surprised by the rather low correlations for some of these traits, such as height and intelligence. I wonder if beauty, perhaps measured by an index of facial symmetry, might exhibit higher correlation values?
Update: An ungated version of the paper.
I used to spend a lot more time talking about cognitive science of religion on this weblog. It was an interest of mine, but I’ve come to a general resolution of what I think on this topic, and so I don’t spend much time discussing it. But in the comments below there was a lot of fast & furious accusation, often out of ignorance. I personally find that a little strange. I’ve been involved in freethought organizations in the past, and so have some acquaintance with “professional atheists.” Additionally, I’ve also been a participant and observer of the internet freethought websites since the mid-1990s (yes, I remember when alt.atheism was relevant!). In other words, I know of whom I speak (and I am not completely unsympathetic to their role in the broader ecology of ideas).
But the bigger issue is a cognitive model of how religiosity emerges. Luckily for me a paper came out which speaks to many of the points which I alluded to, Divine intuition: Cognitive style influences belief in God:
In the comments of my post “Platonism is useful only when it’s useful” several people made a few references to Plato, as well as Platonism. That is fair and makes sense. And there’s a deep strain of anti-Plato sentiment amongst respectable people (e.g., Karl Popper). I assume of the two ancient Greek philosophers of renown, Plato and Aristotle, most readers would be more sympathetic to the latter. He may have gotten a lot wrong, but Aristotle’s more empirical bent is probably more congenial to many moderns than Plato’s greater reliance on abstract theory.
But I don’t think that we can put Platonism at the feet of Plato. There are deep human intuitions about the nature of reality, which Plato and his followers systematized at an early date. But this systematization would have happened at some point in history, and we would have termed it by some name, which would be reviled and lauded by intellectual partisans of a later age.
A new paper in Molecular Psychiatry has been reported on extensively in the media, and readers have mentioned it several times in the comments. I read it. It’s titled Genome-wide association studies establish that human intelligence is highly heritable and polygenic. But the fact is that I read this paper last year. Back then it was titled Common SNPs explain a large proportion of the heritability for human height. I kid, but you get the picture. The new paper establishes for intelligence what we already suspected: most of the genetic variation in this heritable trait is accounted for by numerous genes of small effect. You inherit variants of these numerous genes from your two parents, and your own trait value is to a large extent a combination of the parental values. The issue is not if intelligence is heritable, but the extent of that heritability.
Gregory pressed, asking “Is being gay a choice?”
Pawlenty ultimately said, “I defer to the scientists in that regard.”
Again, Gregory pressed: “So you, you think it’s not a choice. … That you are, as Lady Gaga says, you’re born that way.”
Said Pawlenty: “There’s no scientific conclusion that it’s genetic. We don’t know that. So we don’t know to what extent, you know, it’s behavioral, and that’s something that’s been debated by scientists for a long time. But as I understand the science, there’s no current conclusion that it’s genetic.”