There’s still no expedient reason to believe black-white IQ differences are due to genes – VOX


It is difficult to choose where to start among the commentary that followed our recent discussion of Sam Harris’s interview of Charles Murray on Harris’s Waking Up podcast. In the piece, we argued that Murray was wrong in 1994 in his reading of the evidence for a genetic basis for the black-white IQ inequity — and that he is wrong nowadays. We argued that it was misleading, even irresponsible, for Harris to treat Murray as whether he were someone who merely passes along scientific facts — facts so sound that they can only be doubted by liberals in the grip of “a politically right moral panic,” in Harris’s words.

complete three of us are academic psychologists who gain studied human intelligence, and it is our contention that Murray’s views finish not represent the consensus in our field.

We start by noting that we accepted as facts many claims that are controversial in the academy, whether not in psychology — that IQ exists; that it predicts many life outcomes; that there is a gap between black IQ scores and white IQ scores; that IQ is at least partly heritable (as is nearly every human trait). We rejected the conclusion that Murray and Harris say is virtually inescapable: that it follows that the black-white inequity in IQ must be partly genetic.

Given the response to our first article, we thought it would be useful to clarify the precise boundaries of the dispute, as well as respond to some technical points critics raised.

The central issue at stake is whether the black-white IQ gap is partially genetically determined. We believe there is currently no strong evidence to support this conclusion, whereas Murray presents it as a near certainty, and Harris endorses Murray’s position.

To be honest to our critics, it can be a slight tough at first to pin down Harris and Murray’s position on this point. They both offer broad caveats, like this one, from Harris:

The fact that a trait is genetically transmitted in individuals does not mean that complete the differences between groups or really even any of the differences between groups in that trait are also genetic in origin. [43:25 in the podcast]

But the example he then gives is malnourishment producing differences in height. When speaking approximately IQ, Murray’s position eventually becomes clear: Genes play a role in the average inequity between the IQs of blacks and whites, and public policy is not going to be able to finish much to change levels of cognitive skills.

Referring to the claims he made in The Bell Curve, Murray paraphrases the argument that he and co-author Richard J. Herrnstein made, which Murray says created much of the subsequent controversy:

Our crime in the book was to gain a single solitary paragraph that said … whether we’ve convinced you that either the environmental or the genetic explanation has won out, to the exclusion of the other, we haven’t done a expedient enough job of presenting the evidence for one side or the other. It seems to us highly likely that both genes and the environment gain something to finish with racial differences. And we went no further than that. [59:07]

Harris endorses Murray’s contention approximately partial heritability of the group differences. He says, for example:

This is just straight biology. And because different racial groups differ genetically, to any degree, and because most of what we care approximately in ourselves — intelligence included — … also has some genetic underpinnings — for many of these traits we’re talking approximately something like 50 percent — it would be very, very surprising whether everything we cared approximately was tuned to the exact same population average in every racial group. There’s just virtually no way that’s going to be steady. So based purely on biological consideration, we should expect that for any variable, there will be differences in the average, its average level, across racial groups that differ genetically to some degree. [55:12]

Even when accepting an environmental contribution to black-white differences, Harris still implicitly endorses the understanding that group differences are due to genes:

But again, what we should arrive back to here is that genes are nearly certainly only just section of the record and there should be very likely an environmental contribution here. [58:19]

With statements like these, Harris executes the same swagger Herrnstein and Murray made in The Bell Curve: They acknowledge complete the reasons why the heritability of intelligence doesn’t necessarily mean that group differences are due to genes. They then proceed to draw their conclusions as whether those reasons don’t really matter.

The other side of Murray’s repeated assertions that the black-white IQ gap is partially genetic is his claim that there is ultimately very slight that can be done approximately average levels of IQ; even whether the environment contributes to IQ, any inequalities are basically intractable. Murray again:

There is this notion that whether traits are genetically determined, that’s depraved, and whether traits are environmentally determined, that’s expedient, because we can finish something approximately them whether they are environmental. And whether there is one lesson that we gain learned from the final 70 years of social policy, it is that changing environments in ways that produce measurable results is really, really tough and we actually don’t know how to finish it, no matter how much money we spend. [38:34]

At another point, Murray and Harris are discussing how genetic tendencies can lead children to reshape their environments, and Murray cautions:

Does that mean that whether only you can jack up artificially the environment you’re going to design much inequity in the child’s IQ? And the reply to that is: Not long term. [37:48]

Does adoption count as “jack[ing] up artificially the environment”? In our original post, we pointed out that adoption from a poor domestic to a well-off domestic is associated with a 12- to 18-point gain in IQ. Other studies gain arrive up with slightly lower figures, but the general direction of the finding is beyond dispute.

Similarly, we argued in our initial piece that Murray was not forced to grapple sufficiently with the implications of the Flynn Effect — that is, the remarkable increase in average IQ over generational time: 18 points in the US between 1948 and 2002. These very large increases demonstrate massive, population-level, environmentally caused changes in IQ. Like adoption, the Flynn Effect remains a powerful rebuttal of the understanding that IQ cannot be budged by environmental factors.

Harris brought up the Flynn Effect, and even briefly described it as a challenge, until Murray produced a indistinct quotation to a paper by Wicherts et al. (2004) and Harris gave up. Murray famed that the paper in question is fairly complex, and he is right. Wicherts’s analysis shows that across different IQ subtests, the sample of larger and smaller changes produced by the Flynn Effect is different from the sample of differences between blacks and whites.

Wicherts’s finding has some challenging technical implications, but the essential question remains whether it discredits the Flynn Effect as a challenge to the notion of inborn group differences in cognitive ability. We don’t reflect it does. The Flynn Effect demonstrates massive, population-level environmental changes in average IQ scores; the exact nature of the structure of these changes is an challenging question, but it is a side issue in this context.

So here, then, is where we differ with Murray, and, as we understand it, with Harris: 1) we reflect there is currently no expedient reason to believe that the black-white inequity in average IQ is due to genetic differences between racial groups; and 2) by a long shot than thinking there is no way to influence intelligence by improving the environment, we reflect there is, in fact, expedient reason to believe that improving children’s environments will improve their cognitive skills.

With the terms of the debate established, we now swagger on to some more technical questions raised approximately the topic. Nisbett is primarily responsible for the first section, Harden for the moment, and Turkheimer for the third, although we are complete in agreement on the main points.

Richard Nisbett: who is cherry-picking?

Charles Murray did not write a response to our piece, but he did endorse, on Twitter, the work of several critics. He suggests he might gain written something along the lines of this blog post, which attacked the article on several points. I respond to several of those points here:

finish most experts reflect genes design a substantial contribution to the black-white inequity in intelligence? There gain been several surveys of expert opinion over the years. Perhaps the first was described in a 1988 book by Snyderman and Rothman. The most recent was described in a 2013 blog post approximately a conference presentation. The survey described in that post has resulted in two published articles, neither of which presents data on opinions regarding the black-white inequity. The studies finish, however, report that only approximately 5 percent of people who were invited to participate responded to any one set of items. Given this very low response rate, along with the potential for bias in which scientists were invited in the first dwelling, we doubt that these results are an accurate representation of the field.

Still, in both the Snyderman and Rothman book and in the more recent survey, more than half of respondents selected one of two response categories that included zero (one option was “0 percent of [black-white] differences due to genes” and the other was “0-40 percent of differences due to genes”). Much more essential, however, is that respondents were not allowed to endorse what in my view is the only honest response: It is not possible to give a meaningful estimate of the percentage.

Has the black-white gap in test scores narrowed in the past 25 years? Below are the results of a very large number of psychometric tests of academic achievement assembled by sociologist Sean Reardon. Along the X-axis is the birth year of the cohort. On the Y-axis are the black-white gap and the gap between children of families at the 90th percentile in income and families at the 10th percentile of income, in standard deviation terms (one standard deviation of IQ is equal to 15 points).

The first graph gives the results for reading, the moment for math. For reading, the black-white gap for the 1943 cohort was approximately double the gap associated with family income. The black-white gap then shrank from considerably more than a standard deviation for the 1943 cohort to roughly a standard deviation for the 1963 cohort to slightly more than half a standard deviation for the 2003 cohort. For math, the black-white gap went from around slightly more than a standard deviation to slightly more than half a standard deviation.

IQ is highly correlated with these measures of academic achievement, so it is nearly surely the case that the black-white IQ gap has been very considerably reduced. (The race gap in IQ itself has not to our knowledge been investigated since 2006, when Dickens and Flynn found that it was around 9.5 points, close to what is suggested by Reardon’s achievement data. In the podcast, Murray asserts that the gap is on the order of 15 points.)


Russell Sage Foundation


Russell Sage Foundation

It should be famed that the data for 17-year-olds is comparable to the data overall. (The blog post Murray endorses suggests that the test scores of 17-year-olds reflect genetic influence more than the test scores of 10-year-olds.) The reading gap for 17-year-olds was reduced by 9 points between 1975 and 2012; the math gap was reduced by 4.5 points.

It is steady that the average SAT score of blacks has not changed over the past 20 years. However, black adolescents are much more likely to choose the SAT nowadays than in the 1990s: The number of black people in the US increased by 4 percent from 1996 to 2015, while the number of black SAT takers doubled, far more than the 17 percent increase in the number of white SAT takers. whether the average black IQ is increasing, but the black adolescents from the lower portion of the IQ distribution are increasingly likely to choose the test, this will result in a static mean score.

Are there meaningful limitations to studies on the effect of adoption on IQ? In our original post, we pointed out that adoption from a poor domestic to a well-off domestic is associated with a 12- to 18-point gain in IQ. This point was challenged from several angles.

First, even when adoption produces substantial gains in the average IQs of adopted children, the magnitudes of the individual gains are better predicted by the IQs of the children’s biological parents than by the relative quality of the adoptive environment. This is steady but irrelevant: It is merely evidence that IQ is partly heritable, which no one disputes. That effect (one more time) has no implications for understanding group differences. (The authoritative reference on this phenomenon, by the way, is Turkheimer, 1991.)

What we care approximately is how high their IQs are, not whether the correlation between their IQs and their biological parents is higher or lower than the correlation with the IQs of the adoptive parents. The IQs of those adopted children are considerably higher than they would gain been whether they had been raised by their biological parents.

moment, a preceding study co-authored by Turkheimer found an adoption effect of only approximately 4.4 points. However, the magnitude of the increase afforded by adoption depends on the inequity between the biological and adoptive homes. This specific adoption study was conducted in Sweden, using children adopted from homes of slightly less than average economic status into homes that were slightly higher than average. Krona for krona, the IQ gains were just approximately the same. Again, adoption into improved environments, even in a country with a strong social safety net and relatively slight economic differences between the social classes, increases IQ.

Can educational programs increase IQ? In our original post, we stated that the best early childhood education programs greatly increase educational attainment and labor force participation. A critic alleged that “this was a exceptional straw man,” because would Murray disagree that the best educational programs could raise “social capital”? But throughout the podcast, Murray and Harris are fairly skeptical approximately the opportunity that any policy or intervention could be successful. Their remarks initiate as a discussion approximately IQ specifically, but drift into what sounds like pessimism approximately social policy generally. Murray again:

And whether there is one lesson we’ve learned from the final 70 years of social policy, it is that changing environments in ways that produce measurable results is really, really tough. And we actually don’t know how to finish it, no much how much money we spend. [Harris readily agrees:] Right. [38:49]

I finish not deny the problem of IQ gain fade-out, or the difficulty of designing successful social policies. Indeed, we commented in our original post that IQ gains from programs “tend to regress once the program ends and environmental disadvantages reassert themselves” [emphasis added]. But fade-out on IQ gains does not justify making sweeping statements that we are largely helpless to remedy social inequalities — a claim that Murray has made, in different forms, throughout his career.

Work by the Nobel Prize–winning economist James Heckman has demonstrated that the best early childhood interventions gain a benefit-cost ratio of somewhere between 3:1 and 9:1 by advantage of their effect on such things as lifelong earnings, health costs, crime, and dependence on welfare.

Is the heritability of intelligence “more or less the same” across social classes? In our original post, we wrote, “The heritability of intelligence, although never zero, is markedly lower among American children raised in poverty,” and linked to a 2003 study by Turkheimer and colleagues. That finding suggests that low-income children gain fewer opportunities for their genetic potential to flourish.

Critics gain famed that in a more recent meta-analysis by Tucker-Drob and Bates, the effect size estimated by Turkheimer et al. (2003) was the largest of the studies that tested the interaction. We are fairly familiar with that paper, as Tucker-Drob is Harden’s spouse. However, the same meta-analysis unequivocally demonstrated that the heritability of intelligence is lower among poor children raised in the United States (estimated to be ~26 percent) than among children from wealthy families (estimated to be ~61 percent).


From Tucker-Drob and Bates, 2016, Psychological Science

Furthermore, the meta-analysis tested whether Turkheimer et al. (2003) was a statistical outlier, and it was not; it tested whether the average reduction in heritability was still meaningful when Turkheimer et al. (2003) is left out, and it was; it made the same test leaving out every study Turkheimer had anything to finish with, and the effect was still meaningful.

So despite the misleading impression given by the critics, the meta-analysis was a confirmation of the reduction in heritability among poor Americans. This is essential, because it undermines the hereditarian argument that twin studies demonstrate family environment doesn’t matter for IQ: For poor children in the US, in specific, the family environment seems to matter fairly a bit.

Paige Harden: race and ancestry are not synonymous

Our piece did not contain much information approximately the relationship between genetic ancestry and race, but the brief paragraph that was included motivated objections, most prominently from the author Razib Khan on his blog, Gene Expression.

To back up, in the podcast, Murray states that he has changed not a thing of his views on race and IQ since writing The Bell Curve. In fact, he says (emphasis added):

Now that the genome has been sequenced and so much has been learned since it has been sequenced, the whole discussion of ethnicity-slash-race is being conducted at a much higher level of sophistication. … Now, the ability of the geneticists to simply stare at variation over a million SNPs [single nucleotide polymorphisms] across populations and finish really fascinating cluster analysis. … The word “populations” is what the geneticists like to employ now instead of race, and I don’t blame them, and I’m ecstatic talking approximately populations, too. That’s just being done at a huge level that we never considered. In The Bell Curve, we simply said, whether they call themselves black or Latino or white, we’re going to believe them, and they are going to be our samples. [56:28]

This description inappropriately implies that “populations” defined from genetic analyses and “race” as defined by the US Census categories used in The Bell Curve are essentially the same thing. Elsewhere, Murray speaks of genetic ancestry differences between races as “sign”; the “blurriness” of race is “noise” that “contaminates” the search for genetically based group differences. [57:55]

In response, we wrote: “Murray talks approximately advances in population genetics as whether they gain validated contemporary racial groups. In reality, the racial groups used in the US — white, black, Hispanic, Asian — are such a poor proxy for underlying genetic ancestry that no self-respecting statistical geneticist would undertake a study based only on self-identified racial category as a proxy for genetic ancestry measured from DNA.”

In his critique, Khan responded that “the Census categories are pretty depraved and not optimal (e.g., the ‘Asian American’ category pools South with East & Southeast Asians, and that has caused issues in biomedical research in the past). But the claim is spurious.”

This criticism is confusing, because our claim is essentially the one Khan makes: “Census categories [involving race] are pretty depraved and not optimal.” At the same time, our observation — that statistical geneticists could not publish a study that only controlled for self-identified race by a long shot than genetic ancestry as measured from DNA — is certainly steady. Controlling for multiple dimensions of ancestry derived from genome-wide genotyping is standard practice in genetic research.

I suspect that Khan’s reflexive criticism comes from a dwelling of exasperation with the understanding, still in circulation among some social scientists, that race is “just” a social construct or that the racial categories used in the US nowadays are entirely meaningless. I am sympathetic to this objection to pure social constructivism, and we said in our post that lay notions of race are not wrong or useless. Self-reported racial categories, coarse as they are, also generally reflect underlying differences in genetic ancestry. For instance, in a 2015 paper by Neil Risch et al., which Khan cites extensively, more than 99 percent of people who reported being African American had some proportion of African ancestry.


The Bell Curve cover

But even this close correspondence between African ancestry, as measured from DNA, and self-reported race does not undermine our claim — race is not the same as ancestry. For one, there can be a range of ancestral backgrounds within any one self-identified racial group. whether someone has any African ancestry, you can probably expose with a honest degree of confidence that he or she will identify as black, but the reverse is harder: whether you know someone is black, you finish not know what percentage African versus European versus American ancestry he or she has.

Ancestry also allows for more continual and granular distinctions than our relatively crude categories of race. The ancestry components that geneticists are most commonly including in their analyses are making fine-grained distinctions between people who would complete be lumped together as “white” in the US nowadays.

Finally, we ignore some ancestral differences and focus on others when we categorize people into races. As a historical example, consider Carl Brigham’s 1923 book, A Study of American Intelligence. In a section titled “The Race speculation,” Brigham attempts to classify people from different European countries in terms of their “Nordic,” “Alpine,” and “Mediterranean” blood: The Italians are estimated to be 70 percent Mediterranean; the English as 80 percent Nordic.

The effort to divide Europe’s inhabitants by “blood” is crude, but in one respect, Brigham wasn’t wrong — with contemporary technology, you could certainly differentiate a person with English ancestry from a person with Italian ancestry. But sometime in the past century, we stopped conceptualizing the differences between the English and the Italians in terms of race. We elevate to the status of “race” the distinctions that are our current political and cultural preoccupations, while eliding others.

Ironically, the genetic differences between racial groups are a stout section of why it’s methodologically difficult to resolve the persistent questions approximately the origins of group differences to anyone’s satisfaction. Populations and sub-populations don’t just differ in the frequency of certain genetic variants; they also differ in which variants are present at complete, and in the sample of correlations between genetic variants. Currently, everything we know approximately the specific genetic variants associated with intelligence has been discovered in people of European ancestry, but because of these genetic differences between populations, applying genetic discoveries gleaned from one population to understand another turns out to be very difficult.

Eric Turkheimer: honest and unreasonable conclusions approximately group differences

A widely expressed criticism of our piece is that we misrepresented Murray’s (and Harris’s) conclusions approximately the degree to which IQ differences among racial groups are partly based in genetic differences. As we’ve made clear, there is no question on this point: Both Murray and Harris conclude that racial differences in IQ are at least partly genetic in origin, and base this conclusion on the heritability of IQ scores within populations. As Harris establish it, “This is just straight biology.”

As we famed in our original post, Murray uses a rhetorical swagger to design a genetic account of the IQ gap seem more honest: complete Harris and Murray are saying is that the inequity is probably partly genetic and partly environmental, whereas their opponents insist that it is not genetic at complete. Murray says:

There is an asymmetry between saying probably genes gain some involvement and the assertion that it’s entirely environmental. And that’s the assertion that is being made [by critics]. whether you are going to be upset at The Bell Curve, you are obligated to defend the proposition that the black-white inequity in IQ scores is 100 percent environmental, and that’s a very tough degree. [59:41]

Unfortunately, Murray’s proposal that the IQ gap is the result of a slight genetics and a slight environment does not offer a way out of the scientific and ethical dilemma faced by the (alleged) science of race and behavior. Scientifically, there is no method that can apportion group differences in this way, no empirical analysis that might assign IQ differences between racial groups to one or another source, much less arrive up with a meaningful balance between the two.

There is not a single example of a group inequity in any complex human behavioral trait that has been shown to be environmental or genetic, in any proportion, on the basis of scientific evidence. Ethically, in the absence of a valid scientific methodology, speculations approximately innate differences between the complex behavior of groups remain just that, inseparable from the legacy of unsupported views approximately race and behavior that are as mature as human history. The scientific futility and doubtful ethical status of the enterprise are two sides of the same coin.

To convince the reader that there is no scientifically valid or ethically defensible foundation for the project of assigning group differences in complex behavior to genetic and environmental causes, I gain to swagger the discussion in an even more uncomfortable direction. Consider the assertion that Jews are more materialistic than non-Jews. (I am Jewish, I gain used a version of this example before, and I am not accusing anyone involved in this discussion of anti-Semitism. My point is to interrogate the scientific inequity between assertions approximately blacks and assertions approximately Jews.)

One could try to avoid the question by hoping that materialism isn’t a measurable trait like IQ, apart from that it is; or that materialism might not be heritable in individuals, apart from that it is nearly certain it would be whether someone bothered to check; or perhaps that Jews aren’t really a race, although they certainly differ ancestrally from non-Jews; or that one wouldn’t actually find an average inequity in materialism, but it seems perfectly plausible that one might. (In case anyone is interested, a biological theory of Jewish behavior, by the white nationalist psychologist Kevin MacDonald, actually exists.)

whether you were persuaded by Murray and Harris’s conclusion that the black-white IQ gap is partially genetic, but uncomfortable with the understanding that the same kind of thinking might apply to the personality traits of Jews, I gain one question: Why? Couldn’t there just as easily be a science of whether Jews are genetically “tuned to” (Harris’s phrase) different levels of materialism than gentiles?

On the other hand, whether you no longer believe this mature anti-Semitic trope, is it because some scientific study has been conducted showing that it is spurious? And whether the problem is simply that we haven’t race the studies, why shouldn’t we? Materialism is an essential trait in individuals, and plausibly could be an essential inequity between groups. (Certainly the history of the Jewish people attests to the fact that it has been considered essential in groups!) But the horrific recent history of spurious hypotheses approximately innate Jewish behavior helps us see how scientifically empty and morally bankrupt such ideas really are.

whether Murray and Harris want to design a science out of their intuitions approximately how different groups of people gain been “tuned” to act, they will need to arrive up with a coherent biological account of what precisely genetic “tuning” of behavior entails and how it might be assessed empirically. It is, I acknowledge, a deeply complex question, both philosophically and scientifically.

In fact, I will close by noting that not even the three of us are totally in agreement approximately it: I (Turkheimer) am convinced that the question is irredeemably unscientific; Nisbett accepts it as a valid, lega scientific question, and thinks evidence points fairly strongly in the direction of the black-white gap being entirely environmental in origin; while Harden questions the quality of the existing evidence, but thinks more determinative data may be found in future genetic knowledge.

We agree on this, however: Murray and Harris’s current endorsement of a genetic contribution to the black-white IQ gap is based on a weak brew of unexamined intuition and sketchy empirical evidence. In a free country and a free academy, scientists can speculate approximately whatever they want, but their speculations should not be mistaken for a scientific consensus or a valid, lega basis for social policy.

Eric Turkheimer is the Hugh Scott Hamilton professor of psychology at the University of Virginia. Twitter: @ent3c. Kathryn Paige Harden (@kph3k) is associate professor in the department of psychology at the University of Texas Austin. Richard E. Nisbett is the Theodore M. Newcomb distinguished university professor at the University of Michigan.


The stout understanding is Vox’s domestic for smart discussion of the most essential issues and ideas in politics, science, and culture — typically by external contributors. whether you gain an understanding for a piece, pitch us at [email protected].



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