IQ, heritatility and racism

James Lawler PHIJIML at
Fri Oct 28 08:38:10 MDT 1994

     A master work of empirical analysis on the topic of IQ twenty
years ago was Leon Kamin's book, The Science and Politics of IQ
(John Wiley and Sons, 1974).  Kamin discovered the falsifications
in the works of Cyril Burt.  My own work, IQ, Heritability and
Racism (International Publishers, New York, 1978), was indebted to
Kamin's empirical analyses of the twin studies that had been done
up to that time.  My conceptual arguments and analyses of the
nature of IQ tests were influenced by Marxist writers on this
subject, Brian Simon in England and Lucien Seve in France.  Seve,
by the way, has just published a major work relevant to this topic:
For a Critique of Bioethical Reason (Pour une critique de la raison
bioethique, Editions Odile Jacob, Paris, 1994.)

     Regarding Arthur Jensen's claim that IQ is 80% "heritable", I
made the following argument (135-139), drawn from Richard
Lewontin's "Race and Intelligence", in The IQ Controversy, edited
by N.J. Block and Gerald Dworkin (Pantheon Books, New York, 1976.

     Suppose there are two batches of corn seed, A and B.  All the
seed in A is genetically identical, and all the seed in B is
genetically identical.  But the two batches are genetically
different.  The A seeds are planted in ordinary potting soil, which
gives a variety of different conditions for growth.  And likewise
for the B seeds.  Observed "phenotypic" differences in the height
of the corn in the A group must be entirely due to differences in
the environment of the A seeds.  Because none of the phenotypic
differences in the A corn is due to genotypic differences, the
heritability of the A corn is 0%.  The same is true for the B
group.  Heritability is defined as the ratio of the genotypic
variance over the phenotypic variance.  The common sense
understanding of "heritability" might lead us to think that the
genes in the corn are completely impotent, since both groups are 0%
heritable.  But obviously, if there is an difference between the
average heights of the two groups, we know that this is entirely
due to "heredity".

     On the other hand, suppose that corn is taken from a sack of
an "open pollinated" variety, with a great deal of genetic
variation.  Some of this corn is planted in a carefully controlled
uniform environment A.  Another batch of this corn is sown in
another carefully controlled uniform environment, B.  The two
environments, this time, are quite different.  B has half the
amount of nitrates as A, and also lacks the trace element zinc.
This time, all the phenotypic variance in each environment is due
to the genotypic variance in the corn seed.  Consequently, the
heritability of the corn is 100% in each group.   For common sense,
it might be thought that if "heritability" is as high as 100%, then
nothing can be done to improve the height of the corn.  But the
poor performance of the corn in B, compared to A, is entirely
environmental, and substantial improvements of the B corn are
clearly possible.

     Consequently, even if it were true, as Jensen once argued,
that heritability of intelligence in America were 80%, this tells
us nothing about what can happen if the educational environment of
American children were changed.  Moreover, as the example is meant
to suggest, changes in the environment might easily miss the trace
element by using gross environmental factors such as nitrates, or
throwing money at schools (while leaving unemployment and poverty

     Kamin, by the way, shows that there is no reason to believe
that heritability is other than 0.  The separated twin studies he
examined were greatly flawed since "separation" may have involved
being raised by next door neighbors, or by members of the same
family.  This is like saying that the heritability of corn for all
available soils is 80%, when in fact the variance is always studied
in relatively uniform soils, such as A or B, but not A and B
together.  Kagan's analysis of twenty twins separated by social
class, in which, as reported in recent e-mail discussion, the
average difference in performance was two standard deviations,
confirm Kamin's hypothesis.  (Since the seventies, the major new
development in twin studies was done in Minnesota.  Does anyone
know of a good analysis of these studies?  Also, I would appreciate
the Kagan reference.)

     The reason why we can explain the corn examples so readily is
that in addition to the relative measures of "variance" -- some
corn is above or below the average for its group -- there is also
the possibility of giving absolute measures:  this corn is so many
feet tall.  IQ is a relative measure, telling us that someone is
above or below the average for a given age group.  It does not
measure ability absolutely.  But by a slight-of-hand of IQ theory,
the relative measure has been transformed into an absolute one.
What gives plausibility to this slight-of-hand is the fact that
relative standing on IQ tests tends to remain fairly stable over
time.  Those who are below average at early ages tend to stay that
way as they grow older.   This gives rise to the illusion that
their "intelligence" is fixed.  But the "intelligence quotient" is
only the ratio of their abilities at any given age to the average
performance of their age group.  Intelligence as defined
"absolutely", in terms of what children can actually do with their
minds, is always "developing", at least through their school years,
and hopefully beyond.

     But, you will say, what explains the fact that there is this
stability?  The "developmental" side is a measure of "performance",
something "external".  The ranking stability is a reflection of
differential capacity to learn, something "internal".  Exposed to
the same inputs, Mary will get more out of them than Harry because
of her greater innate capacity to learn.

     One reply to this idea has been developed above.  Even if the
"environment" in a given school *were* uniform, and so the
differences were due to differences in the genes, the conclusion
that there is high heritability for the entire culture cannot be
drawn.  The tremendously great differences between school
environments is not being measured.  High heritability implies that
separated twins who grew up in the substantially different
environments of which everyone is aware would still perform with a
significant degree of similarity.  And there seems to be no
evidence of this.  (And if there were such evidence, this would not
tell us about possibilities under a changed environment.)

     But even within a given school, it is implausible to speak of
a uniform environment.  The very fact of competition establishes
different environments for the children.  Mary normally gets
rewarded by high grades in grade one, while Harry is punished by
lower grades.  Even if the main cause of the different performances
were genetic -- Mary, let us say, matures faster than Harry --
these genetic differences give rise to environmental differences
which make it difficult for Harry to catch up, even if the
genotypic differences are soon cancelled.  Some infants walk sooner
than others.  Suppose we made them compete with one another, giving
love and attention to the fast walkers, while ignoring and sneering
at the slow walkers.  Biological differences that would otherwise
be insignificant in the long run are given social interpretations
that have permanent effects.

     There is at least one more argument that directly challenges
the interpretation of intelligence as a fixed capacity to absorb
information -- something "internal", underlying "external"

     What is the difference between the height of corn and the
intelligence of human beings?  While it is implausible to suppose
that corn will continue indefinitely to improve significantly in
height or in other qualities, the same is not the case for human
beings.  The reason is that human intelligence is not merely a
function of the human organism, but is intrinsically connected to
"tools of thought" -- concepts, methods of thinking, knowledge,
that change historically without any comparable change in the
biological underpinning of intelligence.  This is connected with
what Marx called the "inorganic body" of human beings.  The human
"inorganic brain" constantly develops, while the organic brain
remains relatively fixed.  Intelligence is primarily a function of
this inorganic brain.

     Suppose that identical twins are separated as much as can be
imagined.  Suppose that they have the genes that produce high
"abstract intelligence".  One is raised by hunter-gatherers who
have a counting system that goes from from one to four, while the
other is raised in one of our elite suburban environments.  IQ
testers show that the stone-age twin is best among sixteen-year-
olds in tests that discriminate counting abilities (speed at
counting up to four objects).  The score of the stone-age twin is
a high 140.  The second twin, similarly, ranks in the high
percentiles of American performance, with an IQ of 138.  Such a
result would be the wildest dream of twin studiers.

     But what would it show?  That there is an underlying
differential capacity to absorb a certain kind intellecutal
culture, which we can call intelligence?  But aren't we stretching
concepts tremendously when we say that a modern sixteen year old
with an IQ of 90 is considerably less intelligent than the high IQ
stone age twin?  What does the stone age person know about algebra,
or geometry, or calculus, to say nothing of the concept of zero,
decimals, etc.?  Doesn't "intelligence" itself, however narrowly
defined as "abstract intelligence", evolve with the development of
these ideas?

     Human history is testimony to the tremendous development, in
absolute terms, of certain forms of intelligence -- especially the
"abstract intelligence" that IQ theorists take so seriously.
Scientific knowledge is always growing.  Not only is our
information about the world growing -- the inputs -- but so is our
methods of processing those inputs, our intelligence.

     But a society that succeeded in raising children who were all
at least up to Einstein's level of "performance" would still have
winners and losers according to the metaphysical ideology of "The
Bell Curve".  It will always be possible to manipulate tests to
produce a normal curve distribution of results.  Just as our IQ
testers find no difference in "abstract intelligence" between
stone-age hunters and modern computer hackers, so they will
discount the advances in educational and social life that would
produce a society of creative intellects.  There will still be
differences between those individuals.  They can still be described
in competitive individualistic terms as high and low, winners and
losers.  Though by such a time, for sure, people will be too
intelligent to take such an approach seriously.

--Jim Lawler
Philosophy Department
phijiml at


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