Race-Related IQ

matt spitzer mwspitze at uci.edu
Thu Dec 8 01:03:37 EST 1994

In article <D0EL0J.tx0 at ns1.nodak.edu>, phil at beangenes.cws.ndsu.nodak.edu
(Philip Mcclean) wrote:

> Actually you made the exact argument as to why IQ is analyzed as a quantiative
> trait.  Quantitative traits are traits that are thought to be controlled by
> many genes.  Each of the modular units could be considered a genetic factor
> invovled in determine IQ.  The quantitative geneticist wishes to determine what the
> effects of each of these genes has on IQ.  Unfortunately, they cannot be studied 
> individually, but only as a group.

OK, I suppose I got off on the wrong track when I suggested  that the major
problem was studying the heritability of the composite measure (I'm a
neurobiologist, not a geneticist).  The problem I have is not with studying
heritability of quanitative traits, as you have defined them.  My problem
is with defining IQ as a trait.  It may or may not be possible to study the
heritability of a quantitative trait (I have no basis to form an opinion),
such as grain yield, but at least we can all agree that grain yield is a
quantity that can be measured.  Conversely, once we have measured the
values of grain yield, those measurements have some meaning.  For instance,
if we get more grain we can make more bread.  The same is not true of IQ.  

As far as I know, the only thing IQ has going for it is that it correlates
with academic performance when measured after about age 5.  Big deal. 
There is also a perfect correlation between the growth of my fingernails
and the distance between America and Europe, but nobody is writing books
about it, or studying the heritability of continental drift. 

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