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Environmental variables and group mean cognitive differences, part I

March 3, 2010

While obviously genetic differences exist between groups, they may not fully explain cognitive differences which are observed. Using recent research, I hope to illustrate some associated ‘environmental’ causes of cognitive differences between groups.

Learning and memory are fundamental brain functions affected by dietary and environmental factors. Here, we show that increasing brain magnesium using a newly developed magnesium compound (magnesium-L-threonate, MgT) leads to the enhancement of learning abilities, working memory, and short- and long-term memory in rats. The pattern completion ability was also improved in aged rats. MgT-treated rats had higher density of synaptophysin-/synaptobrevin-positive puncta in DG and CA1 subregions of hippocampus that were correlated with memory improvement. Functionally, magnesium increased the number of functional presynaptic release sites, while it reduced their release probability. The resultant synaptic reconfiguration enabled selective enhancement of synaptic transmission for burst inputs. Coupled with concurrent upregulation of NR2B-containing NMDA receptors and its downstream signaling, synaptic plasticity induced by correlated inputs was enhanced. Our findings suggest that an increase in brain magnesium enhances both short-term synaptic facilitation and long-term potentiation and improves learning and memory functions.

[Slutsky I, Abumaria N, Wu LJ, et al. Enhancement of learning and memory by elevating brain magnesium. Neuron. 2010; 65(2):165-77.]

I eagerly await easily available MgT supplements. Currently, the “Magnesium” you see in stores is actually Magnesium Oxide or some other crap that has difficulty crossing the blood-brain barrier.

How much Magnesium do different groups consume in their diet?

Despite the role of magnesium in maintaining health, much of the U.S. population has historically not consumed adequate amounts of magnesium. Furthermore, significant racial or ethnic disparities in magnesium intake exist. Our objective was to provide more recent data about magnesium intake in the U.S. population. We analyzed the 24-h dietary recall data from 4257 participants aged >or=20 y from the National Health and Nutrition Examination Survey 1999-2000. The median intake of magnesium was 326 mg/d (mean 352 mg/d) among Caucasian men, 237 mg/d (mean 278 mg/d) among African American men, 297 mg/d (330 mg/d) among Mexican American men, 237 mg/d (mean 256 mg/d) among Caucasian women, 177 mg/d (mean 202 mg/d) among African American women, and 221 mg/d (mean 242 mg/d) among Mexican American women. Among men and women, Caucasians had significantly higher mean intakes of dietary magnesium than African Americans but not Mexican Americans. Magnesium intake decreased with increasing age (P for linear trend = 0.035 for Caucasians; P for linear trend <0.001 for African Americans and Mexican Americans). Men had higher intakes of magnesium than women for each of the three race or ethnic groups (P < 0.001 in each group). Caucasian men, African American men and Caucasian women who used vitamin, mineral or dietary supplements consumed significantly more magnesium in their diets than did those who did not. Substantial numbers of U.S. adults fail to consume adequate magnesium in their diets. Furthermore, racial or ethnic differences in magnesium persist and may contribute to some health disparities.

[Ford ES, Mokdad AH. Dietary magnesium intake in a national sample of US adults. J Nutr. 2003; 133(9):2879-82.]

Environmental contaminates like Lead have been shown to be associated with poor cognitive performance. Do disparities in blood lead levels exist between races?

The geometric mean blood lead level declined 41% from 2.76 microg/dL (0.13 micromol/L) in 1988-1994 to 1.64 microg/dL (0.08 micromol/L) in 1999-2002. The percentage of adults with blood lead levels of 10 microg/dL (0.48 micromol/L) or higher declined from 3.3% in 1988-1994 to 0.7% in 1999-2002 (P<.001). In 1999-2002, the multivariable-adjusted odds ratio of having a blood lead level of 10 microg/dL (0.48 micromol/L) or higher was 2.91 (95% confidence interval [CI], 1.74-4.84) and 3.26 (1.83-5.81) for non-Hispanic blacks and Mexican Americans, respectively, compared with non-Hispanic whites. After multivariable adjustment, persons in the highest quartile (>or=2.47 microg/dL [>or=0.12 micromol/L]) compared with those in the lowest quartile (<1.06 microg/dL [<0.05 micromol/L]) of blood lead levels were 2.72 (95% CI, 1.47-5.04) and 1.92 (95% CI, 1.02-3.61) times more likely to have chronic kidney disease and peripheral arterial disease, respectively. In addition, higher blood lead levels were associated with a higher multivariable-adjusted odds ratio of hypertension among non-Hispanic blacks and Mexican Americans.

[Muntner P, Menke A, DeSalvo KB, et al. Continued decline in blood lead levels among adults in the United States: the National Health and Nutrition Examination Surveys. Arch Intern Med. 2005;165(18):2155-61]

What about pregnant women and blood lead levels?

Our results show that calories are positively related to lead level. Insofar as diet serves as amajor vehicle for the ingestion of lead in the United States, our finding is consistent withcalories’ being an indicator of dietary quantity. This finding also agrees with several otherstudies with multivariable analyses that take other nutrients into account (Hammad et al.1996; Lucas et al. 1996) although it does not agree with all (Mahaffey et al. 1986; Mootyet al. 1975).

[Lawrence M Schell, Melinda Denham, Alice D Stark, et al. Blood lead concentration, diet during pregnancy, and anthropometry predict neonatal blood lead in a socioeconomically disadvantaged population. Environ Health Perspect. 2003; 111(2): 195–200.]

How does fetal nutrition further affect offspring?

It is increasingly accepted that alterations of the intrauterine and early postnatal nutritional, metabolic, and hormonal environment may cause predispositions for the development of diseases in later life. Studies in the offspring of diabetic mothers have decisively contributed to this perception. Alterations of the fetal and neonatal environment which offspring of diabetic mothers ‘experience’ seem to program a disposition to develop obesity, diabetes mellitus and Syndrome X-like alterations throughout later life. Underweight at birth is also suggested to lead to an increased risk of Syndrome X in later life (‘Barker hypothesis’). Pathophysiological mechanisms are unclear. Hormones are important environment-dependent organizers of the developing neuro–endocrine–immune network, which finally regulates all fundamental processes of life. When present in non-physiological concentrations during ‘critical periods’ of perinatal life, induced by alterations in the intrauterine or neonatal environment, hormones can act as ‘endogenous functional teratogens’. Perinatal hyperinsulinism is pathognomonic in the offspring of diabetic mothers. Early hyperinsulinism also occurs as a result of early postnatal overfeeding. In rats, endogenous hyperinsulinism, as well as peripheral or only intrahypothalamic insulin treatment during perinatal development, may lead to ‘malprogramming’ of neuroendocrine systems regulating body weight, food intake and metabolism. This results in an increased disposition to become obese and to develop diabetes throughout life. In conclusion, a complex malprogramming of the central regulation of body weight and metabolism may provide a general etiopathogenetic concept, explaining perinatally acquired dispositions, thereby opening a wide field of primary prevention.

[Plagemann A. Perinatal programming and functional teratogenesis: Impact on body weight regulation and obesity. Physiol Behav. 2005;86(5):661-8.]

So-called “metabolic programming” may explain the high rate of obesity and coronary heart disease amongst blacks and Hispanics.

In addition to perinatal diet, maternal stress also plays a role in the state-of-mind of her offspring:

….However, considering that these newborns are brought up by mothers that are themselves stressed, it is more appropriate to define the stress as perinatal rather than simply prenatal, and to take into account postnatal maternal factors as well. It has been suggested that maternal glucocorticoids, one of the most important actors of the HPA axis, underlie the correlation between low birthweight and stress-related cardiovascular, metabolic and neuroendocrine disorders such as hypertension, type 2 diabetes, ischemic heart disease and different types of cognitive and behavioral disorders in adulthood

[Darnaudéry M, Maccari S. Epigenetic programming of the stress response in male and female rats by prenatal restraint stress. Brain Res Rev. 2008;57(2):571-85.]

So, looks like that whole pregnancy thing is kind of important. At least ethnic minorities in the United States take advantage of prenatal care – right?

In 2005, 78% of Hispanic pregnant women and 76% of black non-Hispanic (NH) women, compared with 89% of white NH women in the United States, began PNC in the first trimester

[Kuo TM, Gavin NI, Adams EK, et al. Racial disparities in Medicaid enrollment and prenatal care initiation among pregnant teens in Florida: comparisons between 1995 and 2001. Med Care. 2008;46(10):1079-85.]

Readers are encouraged to contribute.

22 Comments leave one →
  1. March 3, 2010 3:54 pm

    Saw your link at obsidian’s. You make good points. I don’t think the cognitive gaps that exist are 100% genetic either, although I’m sure there is some genetic component to it.
    There are holes to poke in HBD, it’s just obsidian doesn’t actually do it.

    Some things I’ve wondered about HBD are:

    Why are the intelligence distribution curves so similar? The standard deviation is about 15 for each ethnic group, which at first glance looks like the “same seeds sown on different fields” analogy. Why don’t some people groups have really thin curves, and others have really wide ones?

    The mostly fruitless search for “IQ genes” has led most researchers to believe that intelligence is governed by the cumulative effects of hundreds or thousands of genes. If this is the case, then the chances of significant genetic cognitive differences emerging in a few thousand years would appear to be small.

    But the purely environmental explanation leaves much more to be desired. Environmental explanations can not properly account for the IQ findings of interacial adoption studies, twin studies, nor mixed race children.

    In my opinion, this will not be settled until we more fully understand our own biology. Correlations are interesting and demand explanation, but ultimately we will need some more direct cause and effect explanations, especiall in genetics.

    • March 6, 2010 10:45 am

      Why is it necessary for there to be a single intelligence gene in order for intelligence to be substantially heritable? I don’t understand this argument. Just because intelligence is a complex array of genes is no reason to think it isn’t significantly heritable.

      I’ve gone through all the research, and here are the compelling reasons, some mentioned here, why IQ is at least half if not more heritable:

      1) Children of well-to-do blacks vs. children of poor whites vs. adopted East Asian kids. It’s difficult to argue that there’s a substantial positive tilt in prenatal care for poor whites and often-neglected Asian babies. Not buying the prenatal care argument on that account.

      2) To the best of my knowledge, there isn’t a single black community anywhere in the world which outperforms the white average. That’s an awfully suspicious data point if environment is claimed as significant.

      3) The country to which I refer to as the smoking gun for HBD: Qatar. An oil tick welfare state to which many of the excuses that are applied to Africa (malnutrition, pestilence, lack of education) do not apply. According to Lynn their IQ is 78. Even if he is wrong, by how much is he wrong? (Most Arab countries have IQs in the low 80s.) What do they demonstrate to prove otherwise?

      • March 6, 2010 11:17 am

        Let me add that I would love to see studies showing significant disparities between biracial black-white children with white vs. black mothers. If such studies exist, then the environmental angle would be fruitful to pursue.

        However, I have my doubts. It is hard to fathom that well-to-do black women neglect to take doctor-recommended prenatal vitamins (which include magnesium). And that’s when vitamins are most important, no?

        And if they do, is it because they are less intelligent in the first place?

      • March 6, 2010 11:51 am

        And when I say the white average, I mean the worldwide average. The “redleg” example in Barbados sounds interesting. However, we already know that there are white subgroups which lag below the global white average. What we don’t know are any black subgroups which exceed it.

      • March 6, 2010 12:06 pm

        In that last study of welfare mothers (and most of that matter) you find that for a given underclass behavior, underclass blacks are the “worst” so to speak. You can’t really compare underclass whites and underclass blacks. I agree there are genetic racial differences, but cultural differences are incredibly vast.

        I’d be willing to accept that genetic differences related to biochemical processing may also potentiate any environmental affects related to vitamin processing and blood-lead levels. Perhaps blacks simply have more difficulty utilizing vitamins and maintaining them in their bloodstream or removing toxins like lead for that matter? This would be an example of a genetic difference which could be rectified by an environmental change.

      • March 6, 2010 1:47 pm

        “Perhaps blacks simply have more difficulty utilizing vitamins and maintaining them in their bloodstream or removing toxins like lead for that matter?”

        OK — THAT’S an interesting thought.

        Have any studies been done?

  2. March 3, 2010 5:24 pm

    Thanks for the comment; I didn’t know I had to ‘approve’ these things. There are lots of flaws in the HBD sphere and a think a lot of graphs appear to be made because they look pretty, not necessarily because they are accurate.

    I agree that IQ and other things have substantial genetic input and a lot of the ‘environmental’ input (in the first world at least) can’t really be controlled by governments or aid organizations – Education doesn’t hurt though. My main problem with HBDers is the dogmatism and ultra-reductionism behind the arguments put forth by some. You can’t simply use ‘Occam’s razor’ to explain things which you don’t want to bother to know the nuances of.

    Cross-racial adoption/Twin studies still have the variable of prenatal care. If a group or individual mother eats poorly processed chicken and smokes crack and another group or individual mother eats lots of salmon and liver, you’ll notice differences between the two offspring even if they were genetically the same (yet of course we know they aren’t).

    Liberals will be displeased with all this because while these differences will no longer be heavily genetic, they will still be physiological – though at least drugs which effectively alter epigenetic bindings are a little more realistic than ‘gene therapy’ for people who are still alive.

  3. March 3, 2010 6:38 pm

    WordPress lets you open comments so you don’t have to moderate them. You should also play around with new themes asap.

    I agree that many studies do not account for prenatal care. But that doesn’t explain why mixed race kids score in between the respective parental groups. You’d think they’d cluster with either one or the other, according the the prenatal hypothesis.

    Nor does it explain why the children of poor whites outscore the children of affluent blacks on cognitive tests.

    I approached HBD with skepticism also, and do not have all of my sources at my fingertips anymore, but after a year or so of reading on the subject I think that that the HBDers are fundamentally right, although there are questionable claims being made, for certain. Belief in racial egalitarianism amounted to the intellectual equivalent of creationists “poking holes” in Carbon-14 dating methodology and paleontology. Sure, the instruments are perfectly precise, but the overall results do support the hypothesis that evolution did not stop at the neck.

  4. March 3, 2010 6:39 pm

    Should have said “are not perfectly precise”

  5. March 4, 2010 5:39 pm

    I also don’t have a cite, but my understanding is that the offspring of black-white pairings with white mothers have higher IQs than the same pairings with black mothers. You can see this at the individual level with Obama and Alicia Keyes having white mothers while Tay Zonday is the offspring of a black mother and a white father. Massachusetts blacks have higher test scores than Alabama or WV whites – could it be the effects of miscegenation? Dunno.

    • Dwayne Mayor permalink
      March 5, 2010 5:04 pm

      In Moore’s 1986 transracial adoption study, “Family socialization and the IQ test performance of traditionally and transracially adopted Black children,” found that black children adopted by black middle-class families averaged an IQ of 104 as compared to 117 for black children adopted by white middle-class families. The drastically different behaviors of the black mothers (e.g. more critical of child’s mistakes, less encouraging of intellectual exploration, etc.) as compared to the white mothers appeared to have accounted for a large portion of the gap.

      • March 5, 2010 8:35 pm

        That IQ was measured while they were still kids, right? The Minnesota Interracial Adoption Study had similar results when they measured at age 7. It did not last.

        Think of IQ like athletic ability – its easy to train a kid to outperform his untrained peers in an athletic endeavor, but when everyone settles down in their adult life and nobody trains, then performance becomes more of a function of your natural ability as opposed to training regimen.

    • March 6, 2010 11:31 am

      Oh, c’mon Levi? Tay Zonday?

      How about Lenny Kravitz?

  6. March 4, 2010 6:22 pm

    I read somewhere that southern blacks actually have lower levels of white admixture. Additionally, whites down south are predominately Scots/Irish of lower class descent, who have lower IQs than the middle class AngloSaxons who birthed most Northerners. HBD has significant explanatory powers even for American whites.

    An interesting case of socioeconomic/racial flip flop occurs in Barbados, where there are a population of whites called “Redlegs”, who are the descendants of european slaves. They have languished behind the mullatto/black majority for many generations. Populations of European descent can have genetically low average IQs also.

    The main reason why HBD has a hard time being accepted is that social cohesion needs to be maintained. I have doubts that if HBD were widely accepted, it would be a good thing. I agree with Irving Kristol that not all truth is meant for everyone, that some truths are good for the masses, some for the educated, and some for the very educated. HBD is probably best left to the very educated. But when the average citizen is confronted with blatantly anti-meritocratic and destructive policies like AA and illegal immigration being accepted as “a-ok” by both sides of the political spectrum, somebody has to do the dirty work and trot out the HBD data.

  7. March 4, 2010 6:56 pm

    A little bit of knowledge can indeed be a bad thing.

    A great example of this is the current healthcare ‘debate’ where some conservatives yammer on about ‘free markets’ without taking into consideration that “privatized” insurance is responsible for making one of the largest bureaucracies in the world. They took econ101, but apparently didn’t go much further than that.

    I agree that all things being equal, you will notice a relative hierarchy which will develop between groups. How significant these differences are is up for considerable debate, IMO. I’ve been reading the HBD bloggers for probably around 5 years or so now and there is a general aspergery type vibe that ‘if only’ knowledge about genetic differences was widespread, people would immediately agree with their political opinions on the matter. I disagree, I think most people privately acknowledge group differences but, given the opportunity, they may not necessarily politically agree with HBDers on ‘the way things ought to be.’

    • March 4, 2010 8:32 pm

      I like the new look.

      I think most people except for the really dumb and (some of) the really smart buy into the cultural explanation for group cognitive differences, since anyone who implies anything to the contrary is shouted down viciously, even if they are a Nobel Prize winning scientist.

      While political differences would undoubtedly remain on most issues if HBD were acknowledged, I think illegal immigration and amnesty are non-policies and policies respectively that would lose any remnants of public support if Steve Sailer’s PR dream ever came true. The fact that mass illegal immigration will have a significant impact on our national average IQ and its implications are being totally overlooked.

      You can’t run a 1st world country with 3rd world people.

  8. theobsidianfiles permalink
    March 5, 2010 1:14 pm

    Good looking site, and congrats on starting it! I am hopeful that you can not only add to the HBD discussion, but also probe the underlying motivations and ultimate aims of those who are so strident in their support for scientific racism, er, HBD.

    I mean, really, when you get down to it, what is the ultimate point of the HBD crowd? Well, it seems, that they want to use scientific validation to promote “proper” public policies. And let the chips fall where they may. So, if the vast majority of Blacks simply do not belong in thise high status, cushy jobs and instead are better suited to mopping floors in Ms. Ann’s kitchen, then so be it.

    Here’s the problem with that though – the HBD crowd seems to ignore little trifles like, I don’t know, the relatively low birthrate of Smart White folks? It has been shown that having a high IQ tends to erode testosterone. Rushton says this – it’s either more brains, or more dick. So, why don’t the HBD crowd focuses at least as much on this problem, as they do other “eugenics” concerns? I’ve written about this at length, and have been bemused by the utter lack of direct responses on the part of the most ardent HBD types.

    Anyway, again, best of luck in your blogging endeavors!


    • March 6, 2010 10:56 am

      “Here’s the problem with that though – the HBD crowd seems to ignore little trifles like, I don’t know, the relatively low birthrate of Smart White folks? It has been shown that having a high IQ tends to erode testosterone”

      And how exactly would more Smart White Folks(tm) mitigate the issues resulting from PC, AA policies which consider any disparities in performance or outcome as resulting from racism? Methinks it would inflame the dogmatically egalitarian crowd even more. We are talking about social policy here after all.

      Which is why an honest conversation about HBD is a must.

  9. March 9, 2010 2:19 am

    **The drastically different behaviors of the black mothers (e.g. more critical of child’s mistakes, less encouraging of intellectual exploration, etc.) as compared to the white mothers appeared to have accounted for a large portion of the gap.**

    What is also interesting is why Asian adoptees perform above average. There was a good summary on gnxp a few years ago questioning the cultural explanations usually given.

    ” won’t be discussing the obvious mental abilities of South Asian-Americans due to their relative newness and unusual selectivity, but, as seen in Scott’s post below, a frequently raised explanation for why American ethnic groups differ in performance, such as why East Asian-Americans score higher than white Americans in academics and on IQ tests, and also why African-Americans score lower, is that the differences are due to different cultural values (Warren Bell and Jonah Goldberg also raised the culture objection over at National Review to Cochran and Harpending’s Ashkenazi paper). There are a number of reasons to doubt this. For one, the sociological literature doesn’t seem to show it. As Stanley Sue and Sumie Okazaki pointed out in their 1991 American Psychologist paper, Asian American Educational Achievements: A Phenomenon in Search of an Explanation, the parenting styles and values found in East Asian-American homes tend to correlate with lower test scores when they are found in white homes. Further, even according to what we see in Roland Fryer’s newest paper on “acting white”, the idea that blacks have a culture of lower academic values, which is increasingly being embraced by liberals thanks to John Ogbu, is at least highly exaggerated and simply cannot account for the IQ gap. In fact, despite their lower performance, which is genuine, multiple lines of evidence point to African-Americans valuing academics nearly as much as white Americans, if not equally so (for instance spending just as much time on homework. A number of lines of evidence are discussed by Ludwig and Cook in The Black-White Test Score Gap, which you can read here). But an even more profound revelation that causes doubt about cultural explanations is that behavioral genetic experiments show us that home and parental environments don’t seem to matter at all. As fantastic as it may be, at least three big studies now show us that unrelated children raised in the same household, as well as parents and their adoptive children, differ in IQ as much as any two strangers randomly picked from the general population.”

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