From: scott@ailab.ncsu.edu (Scott A Tai)
Subject: Individual and Group Differences in IQ
Reply-To: tai@m-net.ann-arbor.mi.us
Organization: NCSU Artificial Intelligence Systems Laboratory
Date: Thu, 30 Jul 1992 03:08:41 GMT


SANDRA SCARR-SALAPATEK 
COMMENTS ON INDIVIDUAL AND GROUP DIFFERENCES IN I.Q.  
----------------------------------------------------

	Many academic psychologists who once thought I.Q. tests
belonged in the closet with the Rorschach inkblots have now explored
the psychometric literature and found it to be a trove of scientific
treasure.  One of these is Richard Herrnstein, who from a Skinnerian
background has become an admirer of intelligence tests--a considerable
leap from shaping the behavior of pigeons and rats.  Herrnstein's
popular account of I.Q.  testing and its values is generally
responsible, if overly enthusiastic in parts.
	Herrnstein unabashedly espouses I.Q. testing as "psychology's
most telling accomplishment to date", despite the current controversy
over the fairness of testing poor and minority-group children with I.Q.
terms devised by middle-class whites.  His historical review of I.Q.
test development, including tests of general intelligence and multiple
abilities, is interesting and accurate.  His account of the validity
and usefulness of the tests centers on the fairly accurate prediction
that can be made from I.Q. scores about academic and occupational
achievement and income level.  He clarifies the pattern of
relationships between I.Q. and these criterion variables:  High I.Q. is
a necessary but not sufficient condition for high achievement, while
low I.Q. virtually assures failure at high academic and occupational
levels.  One must assume that Herrnstein's enthusiasm for intelligence
tests rests on population statistics, not on predictions for a
particular child, because many children studied longitudinally have
been shown to change I.Q. scores by twenty points or more from
childhood to adulthood.  It is likely that extremes of giftedness and
retardation can be sorted out relatively early by I.Q. tests, but what
about the 95 percent of the population in between?  Their I.Q. scores
may vary from dull to bright normal for many years.  Important
variations in I.Q. can occur up to late adolescence.  On a population
basis, Herrnstein is correct; the best early predictors of later
achievement are ability measures taken from age five on.  Predictions
are based on correlations, however, which are not sensitive to absolute
changes in value, only to rank orders.  This is an important point to
be discussed later.
	After reviewing the evidence for average I.Q.  differences by
social class and race, Herrnstein poses the nature-nurture problem of
"which is primary?" in determining phenotypic differences in I.Q.  For
racial groups, he explains, the origins of mean I.Q. differences are
indeterminate at the present time because we have no information from
heritability studies in the black population or from other,
unspecified, lines of research which could favor primarily genetic or
primarily environmental hypotheses.  He is thoroughly convinced,
however, that individual differences and social-class differences in
I.Q. are highly heritable at the present time and are destined, by
environmental improvements, to become even more so.
	For Herrnstein, society is, and will be even more strongly, a
meritocracy based largely on inherited differences in I.Q.
	Five "corollaries" for the future predict that the heritability
of I.Q. will rise; that social mobility will become more strongly
related to inherited I.Q. differences; that most bright people will be
gathered in the top of the social structure, with the I.Q. dregs at the
bottom; that many at the bottom will not have the intelligence needed
for new jobs; and that the meritocracy will be built not just on
inherited intelligence but on all inherited traits affecting success,
which will presumably become correlated characters.  Thus, from the
successful realization of our most precious egalitarian political and
social goals, there will arise a much more rigidly stratified society,
a "virtual caste system" based on inborn ability.
	To ameliorate this effect, society may have to move toward the
socialist dictum, "From each according to this abilities, to each
according to his needs", but Herrnstein sees complete equality of
earnings and prestige as impossible because high-grade intelligence is
scarce and must be recruited into those critical jobs that require it,
by the promise of high earnings and high prestige.  Although garbage
collecting is critical to the health of the society, almost anyone can
do it; to waste high-I.Q. persons on such jobs is to misallocate scarce
resources at society's peril.
	Herrnstein points to an ironic contrast between the effects of
caste and class systems.  Castes, which established artificial
hereditary limits on social mobility, guarantee the inequality of
opportunity that preserves I.Q. heterogeneity at all levels of the
system.  Many bright people are arbitrarily kept down and many
unintelligent people are artificially maintained at the top.  When
arbitrary bounds on mobility are removed, as in our class system, most
of the bright rise to the top and most of the dull fall to the bottom
of the social system, and I.Q. differences between top and bottom
become increasingly hereditary.  The greater the environmental
equality, the greater the hereditary differences between levels in the
social structure.  The thesis of egalitarianism surely leads to its
antithesis in a way that Karl Marx never anticipated.
	Herrnstein proposes that our best strategy, in the face of
increasing biological stratification, is to publicly recognize genetic
human differences but to reallocate wealth to a considerable extent.
The I.Q. have-nots need not be poor.  Herrnstein does not delve into
the psychological consequences of being publicly marked as genetically
inferior.
	Does the evidence support Herrnstein's view of hereditary
social classes, now or in some future Utopia?  Given his assumptions
about high heritability of I.Q., the importance of I.Q. to social
mobility, and the increasing environmental equality of rearing and
opportunity, hereditary social classes are to some extent inevitable.
But one can question the limits of genetic homogeneity in social-class
groups and the evidence for his syllogism at present.
	Is I.Q. as highly heritable throughout the social structure as
Herrnstein assumes?  Probably not.  In a recent study of I.Q.
heritability in various racial and social-class groups, I found much
lower proportions of genetic variance that would account for aptitude
differences among lower-class than among middle-class children, in both
black and white groups.  Social disadvantage in prenatal and postnatal
development can substantially lower phenotypic I.Q. and reduce the
genotype-phenotype correlation.  Thus, average phenotypic I.Q.
differences between the social classes may be considerably larger than
the genotypic differences.
	Are social classes largely based on hereditary I.Q.
differences now?  Probably not as much as Herrnstein believes.  Since
opportunities for social mobility act at the phenotypic level, there
still may be considerable genetic diversity for I.Q. at the bottom of
the social structure.  In earlier days arbitrary social barriers
maintained genetic variability throughout the social structure.  At
present, individuals with high phenotypic I.Q.'s are often upwardly
mobile; but inherited wealth acts to maintain genetic diversity at the
top, and non-genetic biological and social barriers to phenotypic
development act to maintain a considerable genetic diversity of
intelligence in the lower classes.
	As P.E. Vernon has pointed out, we are inclined to forget that
the majority of gifted children in recent generations have come from
working-class, not middle-class, families.  A larger percentage of
middle-class children are gifted, but the working and lower classes
produce gifted children in larger numbers.  How many more disadvantaged
children would have been bright if they had had middle-class gestation
and rearing conditions.
	I am inclined to think that intergenerational class mobility
will always be with us, for three reasons.  First, since normal I.Q. is
a polygenic characteristic, various recombinations of parental
genotypes will always produce more variable genotypes in the offspring
than in the parents of all social-class groups, especially the
extremes.  Even if both parents, instead of primarily the male,
achieved social-class status based on their I.Q.'s, recombinations of
genes would always produce a range of offspring who would be upwardly
or downwardly mobile relative to their families of origin.
	Second, since, as Herrnstein acknowledges, factors other than
I.Q.--motivational, personality, and undetermined--also contribute to
success or the lack of it, high I.Q.'s will always be found among
lower-class adults, in combination with schizophrenia, alcoholism, drug
addiction, psychopathy, and other limiting factors.  When recombined in
offspring, high I.Q.  can readily segregate with facilitating
motivational and personality characteristics, thereby leading to upward
mobility for many offspring.  Similarly, middle-class parents will
always produce some offspring with debilitating personal
characteristics which lead to downward mobility.
	Third, for all children to develop phenotypes that represent
their best genotypic outcome (in current environments) would require
enormous changes in the present social system.  To improve and equalize
all rearing environments would involve such massive intervention as to
make Herrnstein's view of the future more problematic than he seems to
believe.


-- Scott Tai
   tai@m-net.ann-arbor.mi.us
   157 / 1410 / 9635
Newsgroups: rec.org.mensa