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J. Philippe Rushton and Peer-Review

By Daniel Koffler / November 21, 2007

The last thing I wanted to see happen with my piece on race, genes, and IQ has happened, namely that the comment thread was hijacked by an acolyte of J. Philippe Rushton. Someone who isn't familiar with the relevant literature, or (understandably) doesn't have the time to wade through a few reams of journal articles, could easily walk away with the understanding that there is some impressive body of research supporting Rushton's claims of black racial inferiority.

In fact, one of the most interesting consequences of researching the piece was my discovery that a huge proportion of the popular and academic literature of the last couple of decades supporting the hypothesis of race-linked genetic discrepancies in intelligence is either Rushton's own work or based on his work. This casts the entire discourse in a new light since — as I hope I am going to show — Rushton and his cadre are the 9-11 truthers of social science.

This will shortly get prolix and technical, so the rest is below the fold.

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  • By Anonymous 11/28/07 at 5:05 a.m. UTC

    Koffler,

    I'm sorry to say this but there actually are a huge number of articles on the genes/brains/race/IQ nexus which are not authored by Rushton or Jensen. Here are a few examples.

    Jung et al. 2007:

     

    <blockquote>

    The Parieto-Frontal Integration Theory (P-FIT) of intelligence: converging neuroimaging evidence.

    Jung RE, Haier RJ.

    Departments of Neurology and Psychology, University of New Mexico, Albuquerque, NM 87106, USA. rjung@themindinstitute.org

    "Is
    there a biology of intelligence which is characteristic of the normal
    human nervous system?" Here we review 37 modern neuroimaging studies in
    an attempt to address this question posed by Halstead (1947) as he and
    other icons of the last century endeavored to understand how brain and
    behavior are linked through the expression of intelligence and reason.
    Reviewing studies from functional (i.e., functional magnetic resonance
    imaging, positron emission tomography) and structural (i.e., magnetic
    resonance spectroscopy, diffusion tensor imaging, voxel-based
    morphometry) neuroimaging paradigms, we report a striking consensus
    suggesting that variations in a distributed network predict individual
    differences found on intelligence and reasoning tasks. We describe this
    network as the Parieto-Frontal Integration Theory (P-FIT). The P-FIT
    model includes, by Brodmann areas (BAs): the dorsolateral prefrontal
    cortex (BAs 6, 9, 10, 45, 46, 47), the inferior (BAs 39, 40) and
    superior (BA 7) parietal lobule, the anterior cingulate (BA 32), and
    regions within the temporal (BAs 21, 37) and occipital (BAs 18, 19)
    lobes. White matter regions (i.e., arcuate fasciculus) are also
    implicated. The P-FIT is examined in light of findings from human
    lesion studies, including missile wounds, frontal lobotomy/leukotomy,
    temporal lobectomy, and lesions resulting in damage to the language
    network (e.g., aphasia), as well as findings from imaging research
    identifying brain regions under significant genetic control.<b> Overall,
    we conclude that modern neuroimaging techniques are beginning to
    articulate a biology of intelligence. We propose that the P-FIT
    provides a parsimonious account for many of the empirical observations,
    to date, which relate individual differences in intelligence test
    scores to variations in brain structure and function.</b> Moreover, the
    model provides a framework for testing new hypotheses in future
    experimental designs.

    </blockquote>

     

    Haier et al., 2004

    http://today.uci.edu/news/release_detail.asp?key=1187

    <blockquote>

    Human intelligence determined by volume and location of gray matter tissue in brain

    Single ‘intelligence center’ in brain unlikely, UCI study also finds

    Irvine, Calif. , July 19, 2004

    General human
    intelligence appears to be based on the volume of gray matter tissue in
    certain regions of the brain, UC Irvine College of Medicine researchers
    have found in the most comprehensive structural brain-scan study of
    intelligence to date.

    </blockquote>

     

     

     

    Nature Neuroscience 2004, Thompson and Gray <a href="http://www.loni.ucla.edu/~thompson/PDF/nrn0604-GrayThompson.pdf">original pdf</a>, <a href="http://www.gnxp.com/MT2/archives/002366.html">blog summary</a>:

    <blockquote>

    These are the points reviewed by the article, divided by subheading:

    Neurobiological determinants of intelligence as measured by IQ:

    1. Posterior lesions often cause substantial decreases in IQ. Duncan
      and colleagues suggested that the frontal lobes are involved more in Gf
      and goal-directed behaviour than in Gc (Fig. 2). In addition, Gf is
      compromised more by damage to the frontal lobes than to posterior
      lobe…
    2. MRI-based studies estimate a moderate correlation between brain size and intelligence of 0.40 to 0.51
    3. g was significantly linked to differences in the volume of
      frontal grey matter, which were determined primarily by genetic
      factors… the volume of frontal grey matter had additional predictive
      validity for g even after the predictive effect of total brain volume
      was factored out
    4. Only one region is consistently activated during three
      different intelligence tasks when compared to control tasks…The
      surface features of the tasks differed (spatial, verbal, circles) but
      all were moderately strong predictors of g (g LOADING; range of r,
      0.55–0.67), whereas control tasks were weaker predictors of g (range of
      r, 0.37–0.41). Neural activity in several areas, measured by a positron
      emission tomography (PET) scan, was greater during high-g than low-g
      tasks.
    5. Speed and reliability of neural transmission are related to
      higher intelligence (reviewed in Refs 15,20). Early neuroimaging
      studies using PET found that intelligence correlated negatively with
      cerebral glucose metabolism during mental activity54 (for a review, see
      Ref. 55), leading to the formulation of a 'neural efficiency'
      hypothesis…
    6. Gf is mediated by neural mechanisms that support the
      executive control of attention during working memory…greater
      event-related neural activity in many regions, including the frontal,
      parietal and temporal lobes, dorsal anterior cingulate and lateral
      cerebellum. Crucially, these patterns were most distinct during
      high-interference trials, even after controlling for behavioural
      performance and for activity on low-interference trials within the same
      regions
    7. RAPM scores obtained outside the scanner predicted brain
      activity in a single left parietal/temporal region, and not in the
      frontal lobes.
    8. An exploratory fMRI study60 (n = 7) indicated that parietal
      areas are involved in inspection time tasks, specifically Brodmann area
      (BA) 40 and the ventrolateral prefrontal cortex (BA47) but not the
      dorsolateral prefrontal cortex

    Behavioral Genetics of IQ:

    1. Monozygotic twins raised separately following adoption show a correlation of 0.72 for intelligence
    2. For 48 identical twin pairs separated in early infancy and
      reared apart, Bouchard et al.83 found remarkably high between-twin
      correlations for verbal scores on the WAIS (0.64) and for the first
      principal component of special mental abilities (0.78)
    3. Psychometric g has been shown to be highly heritable in many
      studies, even more so than specific cognitive abilities (h2 = 0.62,
      Ref. 87 compare with Ref. 88; h2 = 0.48, Ref. 89; h2 = 0.6–0.8, Refs
      90,91)…
    4. Intriguingly, the influence of shared family environments on
      IQ dissipates once children leave home — between adult adoptive
      relatives, there is a correlation of IQ of -0.01

    Molecular Genetics of IQ:

    1. Chorney et al.104 discovered an allelic variation in a gene on
      chromosome 6, which codes for an insulin-like growth factor-2 receptor
      (IGF2R), that was linked with high intelligence…
    2. Later studies identified a second IQ-related polymorphism in
      the IGF2R gene, and others in the cathepsin D (CTSD) gene, in the gene
      for an acetylcholine receptor (CHRM2)106, and in a HOMEOBOX GENE (MSX1)
      that is important in brain development107, 108.
    3. Influence of each polymorphism was minimal — variants of
      CHRM2 accounted for a range of only 3–4 IQ points, whereas different
      forms of CTSD accounted for about 3% of the variation between
      people…None of these associations has yet been replicated by other
      research groups
    4. Some patients with microcephaly also possess the ASPM
      mutation, indicating that a shortened version of the gene might lead to
      the development of fewer cerebral neurons and a smaller head.
    5. Polymorphism in the human brain-derived neurotrophic factor (BDNF) gene is associated with impaired performance on memory tests
    6. Catechol-O-methyltransferase (COMT) gene influences the
      activation of working memory circuits. COMT polymorphisms seem to be
      highly specific to some prefrontal cortex-dependent tasks in children.
    7. Dopamine receptor (DRD4) and monoamine oxidase A (MAOA)
      polymorphisms are associated with differences in performance and brain
      activity during tasks that involve executive attention

    …they say "We are not seeking to stimulate research on potential race
    differences in intelligence. Nor can we advocate censorship."…and
    then go on to outline a detailed program for conducting a bulletproof
    version of such a study…

    </blockquote>

    There are is a huge swath of published research in this area broadly supporting the concepts that:

    1) IQ as measured by pen and paper tests is nontrivially correlated with ratio scale measurements like brain volume and reaction times

    2) The correlation improves even further when the regression is upon the volumes of regions involved in cognition

    3) Certain genetic variants (e.g. CHRM2) have been reproducibly associated with cognitive differences

    4) Populations groups have different patterns of genome content (see e.g. Rosenberg et al. Science 2005)

    5) Population groups have different patterns of achievement on IQ tests (too many cites on this to count, but look for example at nationally normed <a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V9F-4JKJSVH-3&_user=145269&_coverDate=07%2F31%2F2006&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000012078&_version=1&_urlVersion=0&_userid=145269&md5=00bebb75c5c3fb1ad967ac6efcb782cb">g proxies</a> like the SAT)

    You are making a mistake if you think that focusing on Rushton and Jensen will make the case. There are a lot of scientists in this area; take a look for example at the most downloaded articles recently published in the journal Intelligence:

    <blockquote>

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