My thoughts on race and IQ

Post by Vipul Naik (regular blogger and site founder, launched site and started blogging March 2012). See:

I’ve been hesitating a bit to get into this topic, not so much because I’m afraid of sharing my views, but because I don’t want to use this blog too much for discussions that are not directly relevant to open borders. However, given that the topic of “race” seems to have come up in Nathan’s recent post, and in BK’s comments, and since I’ve already commented sharing some of my views, I think it’s best that I go on the record with my views. Note that these are just my personal views. I won’t say that they are completely irrelevant to my case for open borders, but what I would say is that the case for open borders is, to my mind, sufficiently robust under changes to my views on this matter. The goal of this post is merely as a reference I can point to so that I can write in the future about these issues without having to provide long justifications and caveats.

To keep this post short, I will not discuss either the moral issues or the relevance to open borders.

I already signed on to the overall IQ consensus (ignoring the racial issues) at the beginning of this post, so I won’t repeat that here. But you might want to take a look at these two consensus statements, this journalistic survey, and this PDF summary by Linda Gottfredson. So here goes.

My understanding of the genetics-focused human biodiversity/race realist position

The genetics-focused human biodiversity/race realist position can be summed up thus. There are, roughly speaking, three sub-races of the human race: Whites, Blacks, and East Asians. Although most population geneticists don’t use the term “race” in their discussions, this tri-racial scheme is reasonably consistent with genetic distance classifications such as the Cavalli-Sforza tree, which identifies 42 subpopulations of the human species.

The race realist position goes on to argue that the mean “genetic IQs” of the three groups are 100, 85, and 105 respectively (some people use different numbers; I’m just using approximate numbers here). Genetic IQ is an ill-defined term, but roughly, you could think of it as meaning what the average IQ would be if they lived in a well-to-do country such as the US with a middle-class lifestyle. The standard deviations within each group is 15 or lower. Thus, blacks are one standard deviation below whites in average IQ.

Caveat 1: Lynn estimates African IQ as about 67, but says that the “genetic IQ” of Africans is probably 80. But I’m rounding that up to 85 since Lynn is relatively extreme. In the comments, BK has pointed out to the work of Jelte Wicherts which casts some doubt on Lynn’s pessimistic estimates, and suggests that current IQ in South Africa is about 80, which suggests that the “genetic IQ” may be around 85 (see also here).

Caveat 2: Some people, such as Lynn, consider genetic attribution of IQ differences even within sub-races and between ethnically similar populations in different regions of the same country. For instance, Lynn applies genetics to considering differences between Northern and Southern Italy. In a critical piece, Ron Unz writes of Lynn:

Although Lynn attributed this large deficit in Southern Italian IQ to substantial North African or Near Eastern genetic admixture, poverty and cultural deprivation seem more likely explanations.

Still, I think Lynn is a bit of an outlier in the fineness with which he makes genetic distinctions and uses admixture to explain differences between nearby regions.

Best data point: The mean IQ of US blacks, who are mostly of African origin, but have some Caucasian admixture, is estimated to be about 83-90, and the US white mean is estimated at about 100, which fits with the above estimates (more here). While there have been claims of a narrowing of the US white-black IQ gap, the evidence is mixed, though a Flynn effect (a secular trend of rising IQ) seems to have been operational for both races over time. If you believe that US blacks’ current IQ largely measures their “genetic IQ” (whichever interpretation you use of the term) then this vindicates some aspects of race realism.

My understanding of the broader human biodiversity position

Some proponents of human biodiversity say that there is no need to be stuck up on genes. The key point to note, from the public policy perspective, is that these differences are unlikely to “Vanish Real Soon” as Steve Sailer puts it in this article:

For purposes of sensible public policy, arguing over whether genetics plays a role in racial differences in achievement is a red herring. What’s crucial to understand is that racial differences—for whatever reasons—are unlikely to vanish Real Soon Now, as all right-thinking people are supposed to assume.

The point I think Sailer is trying to make is that even if culture or other factors, rather than genes, are responsible for these differences, there is no magic wand to fix these factors in the short run, and most of the “obvious” interventions have been tried and shown not to work (more on that later).

My thoughts on the “genetic IQ” concept

My main beef is that I find the concept of “genetic IQ” ill defined and poorly conceived. Yes, there is a heritable component to variation in IQ, and yes, it’s possible that differences in gene frequencies between races is responsible for differences in observed IQs. In fact, I’d be very surprised if none of the genes that affect IQ were found to vary in frequency between human subpopulations. I think a few genes have already been found that affect IQ and differ in frequency between different human subpopulations (I remember seeing a link from a comment somewhere, but I’m not able to dig it up right now, but I’d be happy to add in a link).

But, talk of genetic IQ presupposes a kind of “holding environment constant” or some kind of maximal, optimal environment in which everybody can fulfill their genetic potential. Most IQ “hard hereditarians” hold this sort of view. I think this is plausible, but I have doubts. It’s possible that talk of “genetic IQ” is like talk of “genetic income” — certainly, genes affect income and part of the variation in income is heritable, but the concept of “genetic income” doesn’t make sense. On the other hand, it may be possible that IQ is more like “number of hands” in that there is a genetic predisposition to a certain value, barring specific environmental catastrophes. Of course, these are both extremes. I would be more inclined to believe that IQ is like income, and that the concept of “genetic IQ” as a maximum potential that individuals can achieve is not yet substantiated by the evidence. Long-term secular trends in IQ (the Flynn effect for one) and in income seem to support my point. Incidentally, the fact that interventions to permanently improve IQ have not been clearly established does not, in my view, cut against my point because I think the same is largely true of income. I discuss interventions a couple paras later.

Still, one can define “US middle-class genetic IQ”: what would a person’s IQ be if he/she were raised in a middle-class US household today? If you subscribe to parental irrelevantism, then knowledge of a person’s genome would give you a distribution whose mean would be the “genetic IQ” and whose variance would reflect non-shared (unique) environment factors. This kind of definition is plausible and useful in the context of discussions of the short-run effects of immigration to the United States and child-bearing in the United States, as long as we don’t confuse it with the concept of a maximum potential.

Heritability or at-birthality of IQ at an individual level

Heritability of IQ is high (0.5-0.8) in the US, Sweden, and wherever else it has been studied (including a few studies in India, I believe), but this is heritability within a country or within a certain type of environment, not cross-national heritability. To be clear, there are two types of heritability numbers: narrow-sense heritability (a lower number, which is relevant when using degrees of genetic relatedness between non-identical twins to compute correlations) and broad-sense heritability (a higher number, relevant for identical twins). The narrow-sense heritability of IQ has been lower-bounded at 0.4 or so and the estimate ranges between 0.45 and 0.7 (see here). The broad-sense heritability estimate ranges are between 0.5 and 0.8, with the consensus probably tending to the higher end of the spectrum. The best criticism of high-end estimates is that identical twin estimates may be suffering from the problem of monochorionic twins (see here). If this concern holds up, then perhaps what we call “broad-sense heritability” is better called “at-birthality” because it measures the squared correlation between a kid’s situation at birth and adult IQ rather than the squared correlation between the genome and adult IQ. The estimate of relative importance of post-birth environmental changes would not be affected, as far as I can make out.

The source of the non-heritable (or post-birthal) component of IQ variation within countries is unclear, but it seems not to be due to parenting or anything else that can be explicitly pinned down, but mostly due to “random” variation, what Bryan Caplan might call “free will” and others might call chance. Here’s how Caplan puts it:

I doubt that scientists will ever account for my sons’ differences, because I think their primary source is free will. Despite genes, despite family, despite everything, human beings always have choices–and when we can make different choices, we often do. Some choices are moment-to-moment: To keep working or give up, lie or tell the truth, abandon or defend your views on immigration policy. Other choices are cumulative: You can’t change your weight, education, or income by snapping your fingers, but in the long run they depend on diet, study, and effort–all of which you’re free to choose.

If you want to be more sophisticated, you might want to talk of path dependency. The most interesting theory regarding the non-genetic contributors to individual variation (not just for IQ but for all personalty traits) that I have come across has been offered by Judith Rich Harris in her book No Two Alike.

Some factors that are clearly implicated over the historical long run include nutrition and disease. Malnutrition clearly affects brain development. But it’s generally believed that these factors don’t have a positive effect beyond a point, i.e., they suffer from diminishing returns . The role of cognitive stimuli may also be quite similar, but there is a possibility that variations in some types of cognitive stimuli may be driving individual variation in IQs even in the developed world.

Interventions to improve IQ

First, adult IQ is reasonably stable, probably less stable than adult height but more than adult weight. Thus, the main intervention point for IQ is in childhood, up to the age of 16 or so.

Tons of research suggests that conscious deliberate attempts to environmentally manipulate IQ don’t work. Parental socio-economic status and other measures of the environment seem to have very little effect on adult IQ, per twin/adoption studies. They do affect measured childhood IQ in the short run, but by the time children become adults, the effects of parenting fade out. (Note: This doesn’t mean that children with high childhood IQ and lower adult IQ lost IQ in absolute terms, they just los in measured IQ because IQ measurements are age-adjusted).

On the other hand, the Flynn effect (secular increases in IQ over the past century) suggests that broad environmental changes can affect IQ. The best reconciliation of these results I have seen is a paper by Dickens and Flynn here. But a lot of their conclusions are speculative. Also of interest is Dennis Garlick’s theory of intelligence and the brain in his book. The main reason they offer for why interventions don’t work is that, however intensive they are, people return to the real world sooner or later, and it’s the broad environment of the real world that ultimately shapes their incentives and stimuli. Fade-out is the key here. People who seek intellectual stimulus can often find it in the broader environment even if the particular sub-environment they are in is lacking in that stimulus. For this reason, large environment, in so far as it offers a “menu of options” is more important than the specific parental environment. (Note: This may not be true of measures other than IQ; for instance, measures of academic and scholastic achievement are probably more directly correlated to the quality of your school, but again, adult academic knowledge is probably less correlated with the quality of the school you attended in childhood).

It’s also important not to assume that the Flynn effect will continue to be operational. It may. Or it may not.

What also seems clear is that the Flynn effect doesn’t seem to be causing significant convergence between groups. It’s a “rising tide that lifts all boats” — the future may be different, or it may not.

22 thoughts on “My thoughts on race and IQ”

  1. “human biodiversity/race realist”

    These terms are kind of silly. Everyone familiar with the scientific literature excepts that human populations differ in many respects due to genetic factors: height, disease resistance, coloration, metabolic factors, athletic ability, lactose tolerance, etc. Human populations are clearly diverse in these ways, and population terms like “race” have some correlation (with varying strength depending on local nomenclature conventions) with ancestry and genetics.

    It’s only the magnitude and direction of group differences in economically/politically important psychological traits like IQ and personality that are a hot potato. Identifying these with the anodyne position that there are real significant biological differences (beyond skin color and appearance) as “human biodiversity/race realism” is kind of euphemistic, like “pro-life” and “pro-choice.”

    “The narrow-sense heritability of IQ has been lower-bounded at 0.4 or so and the estimate ranges between 0.45 and 0.7 (see here). The broad-sense heritability estimate ranges are between 0.5 and 0.8, with the consensus probably tending to the higher end of the spectrum. The best criticism of high-end estimates is that identical twin estimates may be suffering from the problem of monochorionic twins (see here).”

    Genetic studies have been able to directly measure relatedness using common SNPs and confirmed high heritability without dependence on twins. These methods intrinsically underestimate heritability because they don’t track all variation, but do give a lower-bound of around 0.5:

    http://infoproc.blogspot.com/2011/08/intelligence-heritable-and-polygenic.html

    However, there is some evidence that heritability is lower for the very poor in the US, at least looking at children (these effects may fade-out, as most things do, but are pretty interesting). Eric Turkheimer is the researcher to read on this.

    “But, talk of genetic IQ presupposes a kind of “holding environment constant” or some kind of maximal, optimal environment in which everybody can fulfill their genetic potential. Most IQ “hard hereditarians” hold this sort of view. I think this is plausible, but I have doubts. It’s possible that talk of “genetic IQ” is like talk of “genetic income” — certainly, genes affect income and part of the variation in income is heritable, but the concept of “genetic income” doesn’t make sense. ”

    Consider height. Genes associated with height vary by region within Europe, and DNA signatures show differential selection by region (bigger differences in frequencies for alleles with bigger effects on height).

    http://infoproc.blogspot.com/2012/08/recent-human-evolution-european-height.html

    There has been a Flynn Effect in height since 1900, a secular increase in heights often attributed to nutrition. However, despite this steady increase in population average height, at any given time the great majority of within-population height is due to genetic variation. And there are systematic interethnic differences in height for kids raised in most every country where these things have been studied.

    Regardless of one’s feelings on “genetic height” as a construct we can make predictions about how population composition changes will affect average population height for any given environment. And the magnitude of those height differences has been pretty steady. Instead of talking about “genetic height” you could talk about group differences in terms of “Danes very strongly tend to be X standard deviations taller than Poles, who strongly tend to be Y standard deviations taller than Italians, across various environments.”

    And for assessing immigration policy the most relevant inferences are predictions about changes in income, IQ, political activity, crime, and so on, and that looks like what’s needed for such predictions.

    “The source of the non-heritable (or post-birthal) component of IQ variation within countries is unclear, but it seems not to be due to parenting or anything else that can be explicitly pinned down, but mostly due to “random” variation, what Bryan Caplan might call “free will” and others might call chance. ”

    Interestingly, a bunch of supposedly non-shared environment is also genetic:

    1. The relatedness between siblings varies (variation in which chromosomes and regions of DNA get passed on), and this is counted as noise:

    http://blogs.discovermagazine.com/gnxp/2012/09/me-my-0-55-brother-against-my-0-45-brother/

    2. Novel mutations, which were not passed from the parents but appear de novo and aren’t shared across siblings..

    “The main reason they offer for why interventions don’t work is that, however intensive they are, people return to the real world sooner or later, and it’s the broad environment of the real world that ultimately shapes their incentives and stimuli. Fade-out is the key here.”

    There seems to be pretty widespread agreement on this point in the psychometric community, including even enthusiasts about interventions.

    1. Thanks for your links. If I understand you correctly, there isn’t any significant point of disagreement between us in our understanding of the consensus. I tried to give relatively conservative estimates and huge ranges to allow for future research overturning minor errors in existing research. That said, there are two points you make that I would like to address further.

      I think the analogies between IQ and height are strong, but I’m not sure whether IQ is more like height or like weight. I suspect it’s something in between in terms of its adult flexibility and the feasibility of childhood interventions in shaping it. But that’s just my guess. I don’t think the evidence is strong enough to rule out that IQ is more like what we know about income: heritability notwithstanding, there is no reason to believe a long-term ceiling on “income potential.” That’s probably not likely, but it’s plausible.

      That said, I think there is an “end of history” type thinking in some hereditarian circles that the developed world has reached the genetic peak potential in terms of height and IQ. I think that’s plausible but I find it unconvincing, largely because of my inherent skepticism of “end of history” type arguments. This isn’t unique to IQ — I find similar arguments unconvincing for income growth, technological growth, and the like. Given that, after several centuries of near-stability, IQ and height both underwent considerable growth in the last century or century and a half (and a similar factoid applies to income and economic growth, which basically started in earnest toward the end of the 18th century after basically millennia of stagnation) I tend to be quite skeptical of the “end of history” flavor of argument.

      But you are right that this is not actually necessary for most of the short-run and some of the long-run arguments. I did, however, want to call out a position I might otherwise be seen as endorsing, even though its importance to the discussion of open borders in the short run is quite limited.

      The other point you make is about the terms like “human biodiversity” and “race realism” — well, I didn’t invent the words. I was just trying to use the terms that people who champion these ideas most publicly have chosen to use. Probably, a lot of people hold somewhat similar views and don’t bother to share them in public, but most of the ones who do talk about these ideas frequently and publicly do seem to use one or both of these labels. If you consider these labels stupid, you might want to convince Steve Sailer and all the other bloggers on his blog roll to stop describing themselves that way.

      1. ” I think there is an “end of history” type thinking in some hereditarian circles that the developed world has reached the genetic peak potential in terms of height and IQ. I think that’s plausible but I find it unconvincing, largely because of my inherent skepticism of “end of history” type arguments.”

        I agree there will be some more gains from environmental change: more computers, riches, drugs, somatic gene therapy, implants, tailored diets, elimination of subtle brain-impairing pollutants and diseases.

        “If you consider these labels stupid, you might want to convince Steve Sailer and all the other bloggers on his blog roll to stop describing themselves that way.”

        It was a critique of their self-description, no onus on you :)

  2. “Still, I think Lynn is a bit of an outlier in the fineness with which he makes genetic distinctions and uses admixture to explain differences between nearby regions.”

    There’s almost no one who would be looking to try, regardless of the validity of the approach. And we now know from genetic data that looking at fine-grained admixture data, measuring genetic ancestry from different parts of Europe, would actually be helpful in explaining fine-grained differences in height between different towns or provinces.

    I think it’s more a lack of funding and good data (genetic data specifically; self-identification is poorly correlated with ancestry in the absence of strong endogamy) that has kept the few interested people looking at large effect size continental ancestry differences (in IQ, medicine and other areas have more funding). But I would bet that when sufficiently large-scale IQ GWAS are performed they will explain a fair bit of intra-continental variation in IQ (and other economically important traits).

    National height data:

    http://en.wikipedia.org/wiki/Human_height#Average_height_around_the_world

    Note the large ethnic differences, even for countries with similar income, such as Denmark vs Hong Kong. Before seeing the data (including noticing it in everyday life) one might not have expected that intergroup differences in height would be so large relative to intragroup variation (within a country, or income level)? After all, why would height be more or less evolutionarily valuable in different regions?

    But the differences are there. The data show that evolutionary pressures and processes varied enough to produce one standard deviation or greater genetic differences (in matched environments) in a variety of highly heritable biological features. So the prior probability for a given feature, like IQ (under condition X) varying on that scale across groups should not be very low. I.e. it is not an extraordinary claim requiring extraordinary evidence, but an ordinary claim requiring ordinary evidence, which the existing literature may provide (for probability but not certainty).

  3. One reason I think people are reluctant to accept the link between genes and IQ the way they accept the link between genes and intelligence is that there are still so many mysteries in philosophy of mind. We know by introspection that minds contain *subjective experience,* and how (if) that can arise from mere physical processes is problematic. (See Thomas Nagel’s latest book, *Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly Wrong.*) No one has created a brain in a laboratory, as experimental scientists often do with the phenomena they study, and as even economists, not noted for being an experimental science, have been able to reproduce supply, demand, and market equilibrium in the lab. The exact process by which genes give rise to intelligence has, I take it, never been described in any detail, if indeed it has been guessed at. It doesn’t hurt to look at data and note correlations. But the fact that the causal link between genes and intelligence remains a black box is a reason to reserve a little refuge of skepticism in the back of one’s mind.

    1. There are a number of identified particular genetic/physiological mechanisms affecting intelligence, both positively and negatively, e.g.: Down’s syndrome, phenylketonuria, torsion dystonia, and Gaucher’s disease.

      http://en.wikipedia.org/wiki/Mental_retardation#Cause
      http://harpending.humanevo.utah.edu/Documents/ashkiq.webpub.pdf

      “One reason I think people are reluctant to accept the link between genes and IQ the way they accept the link between genes and intelligence is that there are still so many mysteries in philosophy of mind.”

      It is a measurable empirical fact, via twin studies, analysis of family members with varying genetic relatedness, and direct genetic measurement of relatedness. How can a belief in immaterial souls or qualia call it into question?

      “No one has created a brain in a laboratory, as experimental scientists often do with the phenomena they study, ”

      This is done at least billions of times every year in labs around the world. Human babies created using sperm and eggs from different parents have systematically different intelligence, as you would predict.

      http://en.wikipedia.org/wiki/Repository_for_Germinal_Choice

      Scientists and breeders can and do breed animals (dogs, flies, mice) for greater or lesser intelligence.

      Denial of the link between genes and intelligence is not like the view that “perhaps God created the universe, and messed around in the history of evolution in a fashion indistinguishable to us from a materialistic universe,” suspiciously unfalsifiable (and not something people would have proposed before old versions of creationism were falsified) but nonetheless compatible with the evidence. It’s more like “humans coexisted with the dinosaurs” creationism, directly contradicting countless observations and requiring massive conspiracies to fake the evidence.

    2. “see Thomas Nagel’s latest book, *Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly Wrong”

      If you’re invoking philosophy, philosophers mostly embrace physicalism, and those who don’t mostly give epiphenomenal-esque accounts, with our behavior determined fully physically. See the large-scale survey of professional philosophers below. If one is going to defer to expert opinion on economics and elsewhere, why not here?:

      http://philpapers.org/surveys/results.pl

      Accept or lean toward: physicalism 526 / 931 (56.5%)
      Accept or lean toward: non-physicalism 252 / 931 (27.1%)
      Other 153 / 931 (16.4%)

      Incidentally, if you’re going to invoke theology as a separate argument (as you suggested in the frontier post, although perhaps referring to the above) they also reject theism:

      Accept or lean toward: atheism 678 / 931 (72.8%)
      Accept or lean toward: theism 136 / 931 (14.6%)
      Other 117 / 931 (12.6%)

      Similar results for top scientists (more extreme the better the scientist, all else equal):

      http://en.wikipedia.org/wiki/Relationship_between_religion_and_science#Studies_of_scientists.27_belief_in_God

      1. The reason I wouldn’t “defer to authority” in this case is because I’ve read a smattering of philosophy of mind, and I think Nagel mops the floor with the alternatives. The physicalist view is a completely unmotivated prejudice. Generally, it’s not really argued for, just assumed. To be more exact, they’re deferring to authority.

    3. I think that there are ways of reconciling Nathan and BK. Some points:

      (1) Heritability measures what happens in practice, not what can happen in principle. Even an observed heritability of 1 is consistent with free will on the matter, it just indicates a lack of differential exercise of free will. Of course, actual heritabilities are far less than 1, leaving ample room for free will. My laptop’s speed and processing abilities are limited by its “genes” but what I actually put in it reflects my “free will.” One reason interventions don’t work is that they are external, not motivated by free will.

      (2) Just because something is stored physically does not mean it is purely physical. Songs, poems, and blog posts are stored physically, but are conceptual constructs. The hard drive of my laptop has stuff physically stored, but its meaning is not purely physical. Studying the physical composition of my laptop hard drive would be a poor way of understanding what is in it, though one could probably have crude “physical correlates.” In other words, physicalism narrowly construed is not incompatible with the spirit of Nathan’s comment.

      The “mind as a machine” metaphor is inapt, but even this analogy points to many possibilities.

      btw, I’m an atheist, but it seems that the free will/determinism/randomness debate is orthogonal to theism. Atheists such as Caplan believe in it, others such as Sam Harris don’t. Within Christianity, Calvinism is deterministic and some sects allow for free will. The majority view you (BK) point to among philosophers is informative, but I wouldn’ t call it an overwhelming consensus one way or the other, allowing all of us to maintain our priors.

          1. I’m aware of these crude definitions, but thanks for pointing them out for the benefit of people reading this thread. Just to clarify, this libertarianism is conceptually independent of political libertarianism. I think, though, that political libertarians are more likely to believe in libertarian free will than the general public.

            It seems to me that the distinction between libertarian free will and compatibilistic free will is a distinction without a difference, at least without a difference from the practical ethics perspective. The distinction seems important from the meta-ethics/metaphysics perspective but not as far as normative and practical ethics and practical philosophy go. But I don’t know enough to comment for sure.

            Anyway, we’ve come a long way from the topic of the original post :).

            1. “It seems to me that the distinction between libertarian free will and compatibilistic free will is a distinction without a difference”

              They make different empirical predictions about how brains work. I’d say the distinction between compatibilism and “no free will” is pure semantics, and doesn’t involve any differences in empirical predictions.

      1. “The majority view you (BK) point to among philosophers is informative, but I wouldn’ t call it an overwhelming consensus one way or the other, allowing all of us to maintain our priors.”

        You know that updating on evidence doesn’t work that way, Vipul. The “other category” (based on discussions with people who put down ‘other’ and their written statements) tends to be filled with people whose views differ in some minor way they emphasize, but in broad meaning those answers don’t differ too much from the distribution of answers to the actual questions.

        For the free will question, compatibilists and “no free will” folk agree on what happens in brains, they just differ over how to describe what’s happening. So for the non-other categories you have a 5.2:1 ratio of support against mystical free will. For atheism vs theism, you have a 5:1 ratio. For physicalism vs non-physicalism you have 2.1:1 (as I said, this differs from the magic free will stuff because the non-physicalists mostly agree that our behavior is determined by physical laws, with the non-physical qualia irrelevant for predictions about the physical world).

        Now consider a question like the existence of the external physical world. There the ratio of opinion is 9:1. So using the log of the support ratio, the rejection of libertarian free will is around two thirds of the way from an evenly balanced controversy to “the external physical world exists.”

        External world: idealism, skepticism, or non-skeptical realism?

        Accept or lean toward: non-skeptical realism 760 / 931 (81.6%)
        Other 86 / 931 (9.2%)
        Accept or lean toward: skepticism 45 / 931 (4.8%)
        Accept or lean toward: idealism 40 / 931 (4.3%)

        “btw, I’m an atheist, but it seems that the free will/determinism/randomness debate is orthogonal to theism.”

        Most belief in libertarian free will among philosophers seems tied to theism, reflecting Catholic and religious institutions for which free will is a religious dogma. If we look at subgroups of philosophers who are enriched (or not) with religious institution faculty and affiliation, such as medieval philosophers (largely a Catholic specialty) and philosophers of religion we see there is a tight correlation between theism and libertarianism:

        http://philpapers.org/surveys/results.pl?affil=Target+faculty&areas0=53&areas_max=1&grain=coarse
        http://philpapers.org/surveys/results.pl?affil=Target+faculty&areas0=22&areas_max=1&grain=coarse

        It looks like the great majority of theists are libertarians about free will. So among non-theists, belief in the falsity of libertarian free will is at least as strong as non-skeptical realism about the external world. So I think the evidence on the evaluation of theism is not irrelevant (and the evidence from the beliefs of eminent scientists, and especially the trend for increasing atheism with increasing quality, provide support beyond that of the philosophers) to the evaluation of libertarian free will claims.

        Caplan is a weird outlier in this area, perhaps because of his strong embrace of intuitionism and strongly Ayn-Rand influenced intuitions.

        1. Obviously, if one uses Bayesian reasoning, even a non-consensus position should be used to update one’s priors.

          But another point I forgot to mention specifically in the context of philosophers is that I would first need to be convinced that their expertise is a valuable one. To take a related example, I *don’t* assume that Christian theologians are experts on the question of whether God exists, although they may be experts on Christian doctrine. Of course, the theologians would describe themselves differently. I’m perhaps less skeptical of philosophers than of Christian theologians, but my overall confidence that they would generally get these things right is not as high as for, say, mathematicians.

          Why I trust mathematicians, and even economists, more than philosophers, is a deep philosophical question that I will get into some other time. It’s relevant to the open borders debate, because most of the estimates at hand have been made by economists and “trust” in economists is therefore crucial to the case.

  4. This is an incredibly refreshing website – an intellectually honest defense of open borders. Sorry I don’t have anything to add beyond that right now.

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