Thursday 12 June 2014

Woodley launches his Victorian defence


You may recall that I promised  in November last year that young Woodley would counter-attack his tormentors, who have now been caught startled, without their gum shields. Vicious uppercuts are battering the proffered chins of his adversaries, the redoubtable Mighty Champion Jim Flynn, a grizzled New Zealand pugilist, mentored by the great Jensen himself; the Australian Ted Nettlebeck, sun-bleached and hardened by the toil of 20 years of inspection time; the experienced Silverman, a quieter fighter, with a good solid punch, the original collector of historical reaction times; and the formidable Russian Dodonov and Dodonova duo, an unusual husband and wife combination of legendary aggression.

After a long wait, in a burst of pent up energy and a flurry of punches, Woodley, te Nijenhuis and Murphy break free, and in a phrase made current by D Day commemorations “all hell breaks loose”. 

The Woodley gang argue that, once they have done a complete re-analysis to respond to the points raised against their original “Victorians” paper, their new results reveal a seemingly robust secular trend towards slowing reaction time in these two countries, which translates into a potential dysgenics rate of −1.21 IQ points per decade, or −13.9 points in total between 1889 and 2004. We conclude by arguing that the best way forward is to test novel predictions stemming from our finding relating to molecular genetics, neurophysiology and alternative cognitive indicators, thus shifting the research focus away from the purely methodological level towards the broader nomological level. We thank our critics for helping us to arrive at a much more precise estimate of the decline in general intelligence.

Michael A. Woodley, Jan te Nijenhuis, Raegan Murphy. Is there a dysgenic secular trend towards slowing simple reaction time? Responding to a quartet of critical commentaries. Intelligence

I highlight Table 1 which shows how the Wechsler subtests relate to simple reaction times and inspection times. What interests me is that the most substantial of the rather low correlations is with Information at 0.3, which does not immediately make sense, unless of course you see reaction time as a measure of crystallized verbal intelligence, which the other correlations with Arithmetic and Vocabulary would tend to confirm. Inspection Time, on the other hand, relates most strongly to Object Assembly 0.393 and Coding 0.351 and Block Design 0.306 which are all Performance subtests. Of course, this table is particularly interesting because of the g loading and heritability data.



I am heartily glad to see this paper published, because I have been sitting on it for many months, awaiting the final permission from the authors, who in turn were waiting for the conclusion of the peer review process, which is intended to achieve a quality standard, which it often achieves. It is not intended to delay the timely publication of academic work, a malign outcome it certainly achieves. A great pity.


  1. I believe this paper demonstrates beyond a reasonable doubt that reaction time has slowed enormously. However, I still doubt that the massive RT slowing translates to a 12-point decline in genotypic g. I suspect that SRT has slowed in part because it is an important ability in its own right, and that modern populations are allocating cognitive development effort to other abilities instead (including the cluster of abilities that constitute ordinary-language intelligence). The CD-IE theory predicts just that –- a decline in some abilities prompted by developmental effort being transferred away from those abilities (a necessary consequence of increased cognitive specialization).

    1. Michael A. Woodley13 June 2014 at 00:02

      Both CD-IE and SLODR effects are most pronounced on abilities exhibiting weak g-loadings. Thus, they are anti-Jensen effects (Jensen, 2003; Woodley, Figueredo, Brown & Ross, 2013). As we see in the present paper, the association between simple RT and IQ is positively mediated by g (it is a Jensen effect). This suggests that it is precisely the sorts of IQ measures that correlate less well with RT that will be most sensitive to these differentiation effects. Moreover, CD-IE in particular explicitly concerns life-history mediated bioenergetic resource allocations amongst specialized cortical real-estates independently of g, which based on the theory relates instead to the effect of underlying pleiotropic mutations on the overall efficiency (in terms of factors such as nerve conduction velocity and plasticity) of the neural architecture (as per Miller's fitness indicator theory; Miller, 2000). Consistent with this prediction (Woodley, 2011), CD-IE effects occur in the absence of any individual-level correlation between life history speed and g (Woodley et al., 2013).

      The bottom line is that g should not be conceived as an ability, but as a highly general and highly heritable feature of neural architecture through which specific abilities more or less (depending on the ability and the task) derive their problem solving capabilities.


      Jensen, A. R. (2003). Regularities in Spearman’s law of diminishing
      returns. Intelligence, 31, 95–105.

      Woodley, M. A. (2011). The cognitive differentiation-integration effort hypothesis: A synthesis between the fitness indicator and life history models of human intelligence. Review of General Psychology, 15, 228-245.

      Woodley, M. A., Figueredo, A. J., Ross, K. C., & Brown, S. D. (2013). Four successful tests of the cognitive differentiation-integration effort hypothesis. Intelligence, 41, 832-842.

      Miller, G. F. (2000). Sexual selection for indicators of intelligence. In
      G. R. Bock, J. A. Goode, & K. Webb (Eds.), The nature of intelligence
      (pp. 260–275). Chichester: Wiley Ltd.

  2. The Jensen effect for SRT does not prove much. Virtually any measure of g or IQ will correlate more with more g-loaded tasks. That's what the positive manifold means.

    I agree with your characterization of g.

  3. "the peer review process, which is intended to achieve a quality standard, which it often achieves. It is not intended to delay the timely publication of academic work, a malign outcome it certainly achieves. A great pity."
    Emil Kirkegaard and I have created a jouirnal which solves this problem. Academic work is preliminarly published on a Forum before final acceptance, and peer review takes place in public view. This has the double advantage of making work instantaneously available without compromising high quality standards required of scientific works.

  4. If I recall, the criticism of Woodley was that the Victorian samples he studied were far too elite to be comparable with modern samples. The people who Galton tested probably had g in the top 1% of Victorians, and thus can not be compared with modern university students who typically have IQ's in the top 33% of their generation. That's a 2 SD difference in selectivity.

    Did Woodley rebut this criticism? I skimmed the paper, but didn't notice this issue addressed, though I probably missed it.

    1. "The people who Galton tested probably had g in the top 1% of Victorians"


      On this blog Michael has an old essay addressing the selectivity argument.

    2. They were in the top 1% in social class (not g as I incorrectly asserted), but I don't think that distorted Woodley's results too much because the correlation between reaction time and social class is low, especially for people in their 20s.

      I agree with Woodley's general conclusion, though in my humble opinion, the effect size he claims is double what it should be because of an inappropriate statistical correction:

      Pumpkin Person