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1854[evol-psych] Re: Iq" genetic or environmental?

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  • Mark Macnair
    Dec 2, 1999
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      > I suspect many people are upset at having to multiply for IQ
      > i.e. Iq = G*E
      > and find that something seems to be missing. Of course, it is
      > missing.
      > Can simple multiplication be the best model for something so
      > complex
      > when it does not suffice even for freshman physics which
      > describes
      > point masses, acceleration along straight lines, massless springs
      > etc
      > of nonvolitional dead bodies?
      I know of no quantitative genetic model that would say
      IQ=G*E. The standard model is additive:
      P=A+D+E+G*E+I etc
      where P is the phenotype (IQ in this case) , A is the
      Additive genetic effect, and D the non-additive effect (ie
      dominance); E is the effect of the environment. G*E is not
      a multiplicative function, but a statistical inteaction, as
      are gene x gene interactions (I).

      These terms are all pretty meaningless when applied to
      individuals, but are easily interpreted as VARIANCES (when
      poplation diffrences in these terms can be determined).

      If you have suitable data (difficult to get for humans and
      IQ, but easy for plants and other phenotypes) you can get
      estimates of all these terms and show that this additive
      model of gene action is pretty good.

      Why should IQ be any difefrent to any other character in
      humans, animals or plants?

      > I think they want a more complex mathematical model which is
      > better at
      > taking into account much of the evidence from real life. For
      > example,
      > they might want an equation that does something like "if the
      > genetic
      > disposition is low...etc etc."
      This contingent type model will come out in G*E term of the
      standard model.

      Mark Macnair
      Professor of Evolutionary Genetics
      Director of Postgraduate Studies
      Hatherly Laboratories
      Department of Biological Sciences
      University of Exeter
      Prince of Wales Rd
      Exeter EX4 4PS

      Tel: 44 (0) 1392 263791
      Fax: 44 (0) 1392 263700
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