Post by M WintherThe Flynn effect has already peaked in many Western countries. American
Blacks have peaked long ago at IQ 85................
The point is that an IQ of 85 in 2000 reflected a very different
performance than did an IQ of 85 in 1950.
Post by M WintherThis religious belief in everybody's
equal
capacities is ridiculous. If it's not the Master Race, then it's The
Glorious
Egalitarian Unity of Mankind. Soon people will drop back to madness
racialism.
So it goes, back and forth, simply because people refuse to settle at a
balanced
viewpoint.
Why do you think that your viewpoint is balanced? It seems to me that
you identify with the views of Jensen/Rushton/Lynn etc and reject or
don't even consider the views of Flynn/Dickens/Nisbett etc. I don't
think firm conclusions are justified given the limitations of our
present knowledge -- even the basic concepts of intelligence and race
can not be clearly defined and measured. I think the conclusions of
an American task force, published some years ago, are appropriately
cautious and judicious:
http://www.psych.illinois.edu/~broberts/Neisser%20et%20al,%201996,%20intelligence.pdf
Because there are many ways to be intelligent, there are
also many conceptualizations of intelligence. The most
influential approach, and the one that has generated the
most systematic research, is based on psychometric testing.
This tradition has produced a substantial body of
knowledge, though many questions remain unanswered.
We know much less about the forms of intelligence that
tests do not easily assess: wisdom, creativity, practical
knowledge, social skill, and the like.
Psychometricians have successfully measured a wide
range of abilities, distinct from one another and yet intercorrelated.
The complex relations among those abilities
can be described in many ways. Some theorists focus on
the variance that all such abilities have in common, which
Spearman termed g ("general intelligence"); others prefer
to describe the same manifold with a set of partially independent
factors; still others opt for a multifactorial description
with factors hierarchically arranged and something
like g at the top. Standardized intelligence test scores
("IQs"), which reflect a person's standing in relation to
his or her age cohort, are based on tests that tap a number
of different abilities. Recent studies have found that these
scores are also correlated with information processing
speed in certain experimental paradigms (choice reaction
time, inspection time, evoked brain potentials, etc.), but
the meaning of those correlations is far from clear.
Intelligence test scores predict individual differences
in school achievement moderately well, correlating about
.50 with grade point average and .55 with the number of
years of education that individuals complete. In this context
the skills measured by tests are clearly important.
Nevertheless, population levels of school achievement are
not determined solely or even primarily by intelligence
or any other individual-difference variable. The fact that
children in Japan and Taiwan learn much more mathematics
than their peers in America, for example, can be
attributed primarily to differences in culture and schooling
rather than in abilities measured by intelligence tests.
Test scores also correlate with measures of accomplishment
outside of school, e.g., with adult occupational
status. To some extent those correlations result directly
from the tests' link with school achievement and from
their roles as "gatekeepers." In the United States today,
high test scores and grades are prerequisites for entry into
many careers and professions. This is not quite the whole
story, however: a significant correlation between psychometric
intelligence and occupational status remains even
when measures of education and family background have
been statistically controlled. There are also modest (negative)
correlations between intelligence test scores and
certain undesirable behaviors such as juvenile crime.
Those correlations are necessarily low: all social outcomes
result from complex causal webs in which psychometric
skills are only one factor.
Like every trait, intelligence is the joint product of
genetic and environmental variables. Gene action always
involves a (biochemical or social) environment; environments
always act via structures to which genes have contributed.
Given a trait on which individuals vary, however,
one can ask what fraction of that variation is associated
with differences in their genotypes (this is the heritability
of the trait) as well as what fraction is associated with
differences in environmental experience. So defined, heritability
(h a) can and does vary from one population to
another. In the case of IQ, h 2 is markedly lower for children
(about .45) than for adults (about .75). This means
that as children grow up, differences in test scores tend
increasingly to reflect differences in genotype and in individual
life experience rather than differences among the
families in which they were raised.
The factors underlying that shift--and more generally
the pathways by which genes make their undoubted
contributions to individual differences in intelligence--
are largely unknown. Moreover, the environmental contributions
to those differences are almost equally mysterious.
We know that both biological and social aspects
of the environment are important for intelligence, but we
are a long way from understanding how they exert their
effects.
One environmental variable with clear-cut importance
is the presence of formal schooling. Schools affect
intelligence in many ways, not only by transmitting specific
information but by developing certain intellectual
skills and attitudes. Failure to attend school (or attendance
at very poor schools) has a clear negative effect on intelligence
test scores. Preschool programs and similar interventions
often have positive effects, but in most cases
the gains fade when the program is over.
A number of conditions in the biological environment
have clear negative consequences for intellectual
development. Some of these--very important when they
occur--nevertheless do not contribute much to the population
variance of IQ scores because they are relatively
rare. (Perinatal complications are one such factor.) Exposure
to environmental lead has well-documented negative
effects; so too does prenatal exposure to high blood
levels of alcohol. Malnutrition in childhood is another
negative factor for intelligence, but the level at which its
effects become significant has not been clearly established.
Some studies suggest that dietary supplements of certain
micro-nutrients can produce gains even in otherwise wellnourished
individuals, but the effects are still controversial
and there has been no long-term follow-up.
One of the most striking phenomena in this field is
the steady worldwide rise in test scores, now often called
the "Flynn effect." Mean IQs have increased more than
15 points--a full standard deviation--in the last 50 years,
and the rate of gain may be increasing. These gains may
result from improved nutrition, cultural changes, experience
with testing, shifts in schooling or child-rearing
practices, or some other factor as yet unknown.
Although there are no important sex differences in
overall intelligence test scores, substantial differences do
appear for specific abilities. Males typically score higher
on visual-spatial and (beginning in middle childhood)
mathematical skills; females excel on a number of verbal
measures. Sex hormone levels are clearly related to some
of these differences, but social factors presumably play a
role as well. As for all the group differences reviewed here,
the range of performance within each group is much larger
than the mean difference between groups.
Because ethnic differences in intelligence reflect
complex patterns, no overall generalization about them
is appropriate. The mean IQ scores of Chinese and Japanese
Americans, for example, differ little from those of
Whites though their spatial ability scores tend to be
somewhat higher. The outstanding record of these groups
in terms of school achievement and occupational status
evidently reflects cultural factors. The mean intelligence
test scores of Hispanic Americans are somewhat lower
than those of Whites, in part because Hispanics are often
less familiar with English. Nevertheless, their test scores,
like those of African Americans, are reasonably good
predictors of school and college achievement.
African American IQ scores have long averaged
about 15 points below those of Whites, with correspondingly
lower scores on academic achievement tests. In
recent years the achievement-test gap has narrowed appreciably.
It is possible that the IQ-score differential is
narrowing as well, but this has not been clearly established.
The cause of that differential is not known; it is
apparently not due to any simple form of bias in the
content or administration of the tests themselves. The
Flynn effect shows that environmental factors can produce
differences of at least this magnitude, but that effect
is mysterious in its own right. Several culturally-based
explanations of the Black/White IQ differential have been
proposed; some are plausible, but so far none has been
conclusively supported. There is even less empirical support
for a genetic interpretation. In short, no adequate
explanation of the differential between the IQ means of
Blacks and Whites is presently available.
It is customary to conclude surveys like this one
with a summary of what has been established. Indeed,
much is now known about intelligence. A near-century
of research, most of it based on psychometric methods,
has produced an impressive body of findings. Although
we have tried to do justice to those findings in this report,
it seems appropriate to conclude on a different note. In
this contentious arena, our most useful role may be to
remind our readers that many of the critical questions
about intelligence are still unanswered. Here are a few of
those questions:
1. Differences in genetic endowment contribute substantially
to individual differences in (psychometric) intelligence,
but the pathway by which genes produce their
effects is still unknown. The impact of genetic differences
appears to increase with age, but we do not know why.
2. Environmental factors also contribute substantially
to the development of intelligence, but we do not
clearly understand what those factors are or how they
work. Attendance at school is certainly important, for
example, but we do not know what aspects of schooling
are critical.
3. The role of nutrition in intelligence remains
obscure. Severe childhood malnutrition has clear negative
effects, but the hypothesis that particular "micronutrients"
may affect intelligence in otherwise adequately-
fed populations has not yet been convincingly
demonstrated.
4. There are significant correlations between measures
of information-processing speed and psychometric
intelligence, but the overall pattern of these findings yields
no easy theoretical interpretation.
5. Mean scores on intelligence tests are rising steadily.
They have gone up a full standard deviation in the last
50 years or so, and the rate of gain may be increasing.
No one is sure why these gains are happening or what
they mean.
6. The differential between the mean intelligence test
scores of Blacks and Whites (about one standard deviation,
although it may be diminishing) does not result from
any obvious biases in test construction and administration,
nor does it simply reflect differences in socioeconomic
status. Explanations based on factors of caste and
culture may be appropriate, but so far have little direct
empirical support. There is certainly no such support for
a genetic interpretation. At present, no one knows what
causes this differential.
7. It is widely agreed that standardized tests do not
sample all forms of intelligence. Obvious examples include
creativity, wisdom, practical sense, and social sensitivity;
there are surely others. Despite the importance
of these abilities we know very little about them: how
they develop, what factors influence that development,
how they are related to more traditional measures.
In a field where so many issues are unresolved and
so many questions unanswered, the confident tone that
has characterized most of the debate on these topics is
clearly out of place. The study of intelligence does not
need politicized assertions and recriminations; it needs
self-restraint, reflection, and a great deal more research.
The questions that remain are socially as well as scientifically
important. There is no reason to think them unanswerable,
but finding the answers will require a shared
and sustained effort as well as the commitment of substantial
scientific resources. Just such a commitment is
what we strongly recommend.