Spearman’s theory

Shouldn’t Spearman’s hypothesis have graduated to the level of theory by now?

McDaniel and Kepes, unpublished. Spearman’s Hypothesis Is a Model for Understanding Alternative g Tests

Periodically, researchers claim to have developed an alternative general cognitive ability (g) test that assesses g but exhibits lower than typically found mean racial differences. To the extent that such measures have reduced mean racial differences, we argue that they have less g saturation (i.e., they measure g less well) and will have lower validity and larger prediction errors than tests with high g saturation. Using a sample of 22,728 people from the General Aptitude Test Battery database, we show that one can decrease mean racial differences in a g test by altering the g saturation of the test. Consistent with Spearman’s Hypothesis, the g saturation of a test is positively, and strongly, related to the magnitude of White-Black mean racial differences in test scores. We demonstrate that the reduction in mean racial differences accomplished by reducing g saturation in a test is obtained at the cost of lower validity and increased prediction errors. We recommend that alternative g tests be evaluated in comparison to highly g saturated tests with respect to Spearman’s Hypothesis, test validity, and prediction errors

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13 Responses to Spearman’s theory

  1. Steve Sailer says:

    It’s only 108 years old!

  2. Kiwiguy says:

    Try telling that to TomDebb (?) on straight dope – he still thinks g is just a fiction.

  3. Kiwiguy says:

    *** We demonstrate that the reduction in mean racial differences accomplished by reducing g saturation in a test is obtained at the cost of lower validity and increased prediction errors. ***

    Which of course was what happened with the efforts to reduce disparate impact – nice case study here.

    http://www.ipacweb.org/files/nassau/gottfredson3.html

  4. x says:

    does anybody remember that lengthy, obscure piece by cosma shalizi that a lot of more educated egalitarians loved to run around with posting everywhere (without understanding it, most likely) that claimed to have debunked ‘spearman’s g’?

    • Chuck11 says:

      Ya, MIke the Mad Biologist recently flung that post in my face it in reply to my cognitive realist commentaries on one of this anti-Derb posts. I pointed him to the following study which demolished Cosma’s claim:
      http://www.sciencedirect.com/science/article/pii/S0160289607000931

      “In a recent paper, Johnson, Bouchard, Krueger, McGue, and Gottesman (2004) addressed a long-standing debate in psychology by demonstrating that the g factors derived from three test batteries administered to a single group of individuals were completely correlated. This finding provided evidence for the existence of a unitary higher-level general intelligence construct whose measurement is not dependent on the specific abilities
      assessed. In the current study we constructively replicated this finding utilizing five test batteries. The replication is important because there were substantial differences in both the sample and the batteries administered from those in the original study.”

      It left him sputtering. For reference, Cosma claimed that g was an artifact of subtest similarities (i.e., test makers used cognitively similar questions and so performance correlated.) It’s not, as demonstrated by the study cited above. And g is the mostly highly biologically and genetically correlated cognitive factor so it’s difficult to see how it could be an artifact. Cosma’s post, written in 2007 or 2008, was dated by at least a decade.

      • Teaters says:

        I see that post (It’s Not Just Derbyshire: Charles Murray Can’t Answer the Question Either). Did Mike ever leave a comment?

      • Chuck11 says:

        “I see that post (It’s Not Just Derbyshire: Charles Murray Can’t Answer the Question Either). Did Mike ever leave a comment?”

        I’m still waiting.

  5. Kiwiguy says:

    I see you answered that point on the West Hunter blog also. Here was my comment regarding Shalizi:

    “***Have you considered Cosma Shalizi’s essay on g?***

    As Steve Hsu has pointed out, anyone who understands factor analysis realises that you can have correlations and a single largest factor even if there are no underlying causal reasons (i.e., it is just an accident). Nonetheless, these models may still be useful.

    Prior to the availability of molecular studies the heritability of type II diabetes was estimated at 0.25 using all those methods. Now molecular studies have identified at least 9 loci involved in the disease. There are other examples in relation to height. So you can’t say that heritability studies, with all their seemingly ridiculous assumptions, are worthless.

    In fact, reading Shalizi closely, you’ll see that he doesn’t think they are either. For instance, he says:

    ***If you put a gun to my head and asked me to guess [whether there are genetic variants that contribute to IQ], and I couldn’t tell what answer you wanted to hear, I’d say that my suspicion is that there are, mostly on the strength of analogy to other areas of biology where we know much more. ***

    Also, in his article on g he seems to accept in the footnotes that intelligence or cognitive ability, as operationally defined by psychologists, is important for economic development.”

    http://westhunt.wordpress.com/2011/11/14/six-black-russians/#comment-211

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