Linux-Advocacy Digest #698, Volume #32 Thu, 8 Mar 01 01:13:07 EST
Contents:
Re: What does IQ measure? (The Danimal)
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Date: Thu, 08 Mar 2001 00:22:12 -0500
From: The Danimal <[EMAIL PROTECTED]>
Crossposted-To:
alt.destroy.microsoft,comp.os.ms-windows.advocacy,comp.os.ms-windows.nt.advocacy,soc.singles
Subject: Re: What does IQ measure?
CR Lyttle wrote:
>
> Donovan Rebbechi wrote:
> >
> > I'll butt in here and say that IQ is certainly not a terribly reliable measure
> > of anything, but it's true that it correlates with a "intelligence", no matter
> > how you define "intelligence".
> >
> So which has higher intelligence, an oak forest, or amoebae? Trees do
> communicate, and forest do learn.
Let's have them play chess.
A considerably better read than this thread appeared recently
in Scientific American:
http://www.sciam.com/specialissues/1198intelligence/1198gottfred.html
The General Intelligence Factor
Despite some popular assertions,[*] a single factor for intelligence,
called g, can be measured with IQ tests and does predict success in life
by Linda S. Gottfredson
[*hi jackie---this repost is for you]
No subject in psychology has provoked more intense public controversy
than the study of human intelligence. From its beginning, research on
how and why people differ in overall mental ability has fallen prey
to political and social agendas that obscure or distort even the most
well-established scientific findings. Journalists, too, often present
a view of intelligence research that is exactly the opposite of what
most intelligence experts believe. For these and other reasons,
public understanding of intelligence falls far short of public
concern about it. The IQ experts discussing their work in the public
arena can feel as though they have fallen down the rabbit hole into
Alice's Wonderland.
The debate over intelligence and intelligence testing focuses on the
question of whether it is useful or meaningful to evaluate people
according to a single major dimension of cognitive competence. Is
there indeed a general mental ability we commonly call
"intelligence," and is it important in the practical affairs of life?
The answer, based on decades of intelligence research, is an
unequivocal yes. No matter their form or content, tests of mental
skills invariably point to the existence of a global factor that
permeates all aspects of cognition. And this factor seems to have
considerable influence on a person's practical quality of life.
Intelligence as measured by IQ tests is the single most effective
predictor known of individual performance at school and on the job.
It also predicts many other aspects of well-being, including a
person's chances of divorcing, dropping out of high school, being
unemployed or having illegitimate children [see illustration].
By now the vast majority of intelligence researchers take these
findings for granted. Yet in the press and in public debate, the
facts are typically dismissed, downplayed or ignored. This
misrepresentation reflects a clash between a deeply felt ideal and a
stubborn reality. The ideal, implicit in many popular critiques of
intelligence research, is that all people are born equally able and
that social inequality results only from the exercise of unjust
privilege. The reality is that Mother Nature is no egalitarian.
People are in fact unequal in intellectual potential--and they are
born that way, just as they are born with different potentials for
height, physical attractiveness, artistic flair, athletic prowess and
other traits. Although subsequent experience shapes this potential,
no amount of social engineering can make individuals with widely
divergent mental aptitudes into intellectual equals.
Of course, there are many kinds of talent, many kinds of mental
ability and many other aspects of personality and character that
influence a person's chances of happiness and success. The functional
importance of general mental ability in everyday life, however, means
that without onerous restrictions on individual liberty, differences
in mental competence are likely to result in social inequality. This
gulf between equal opportunity and equal outcomes is perhaps what
pains Americans most about the subject of intelligence. The public
intuitively knows what is at stake: when asked to rank personal
qualities in order of desirability, people put intelligence second
only to good health. But with a more realistic approach to the
intellectual differences between people, society could better
accommodate these differences and minimize the inequalities they
create.
Extracting g
Early in the century-old study of intelligence, researchers
discovered that all tests of mental ability ranked individuals in
about the same way. Although mental tests are often designed to
measure specific domains of cognition--verbal fluency, say, or
mathematical skill, spatial visualization or memory--people who do
well on one kind of test tend to do well on the others, and people
who do poorly generally do so across the board. This overlap, or
intercorrelation, suggests that all such tests measure some global
element of intellectual ability as well as specific cognitive skills.
In recent decades, psychologists have devoted much effort to
isolating that general factor, which is abbreviated g, from the other
aspects of cognitive ability gauged in mental tests.
The statistical extraction of g is performed by a technique called
factor analysis. Introduced at the turn of the century by British
psychologist Charles Spearman, factor analysis determines the minimum
number of underlying dimensions necessary to explain a pattern of
correlations among measurements. A general factor suffusing all tests
is not, as is sometimes argued, a necessary outcome of factor
analysis. No general factor has been found in the analysis of
personality tests, for example; instead the method usually yields at
least five dimensions (neuroticism, extraversion, conscientiousness,
agreeableness and openness to ideas), each relating to different
subsets of tests. But, as Spearman observed, a general factor does
emerge from analysis of mental ability tests, and leading
psychologists, such as Arthur R. Jensen of the University of
California at Berkeley and John B. Carroll of the University of North
Carolina at Chapel Hill, have confirmed his findings in the decades
since. Partly because of this research, most intelligence experts now
use g as the working definition of intelligence.
The general factor explains most differences among individuals in
performance on diverse mental tests. This is true regardless of what
specific ability a test is meant to assess, regardless of the test's
manifest content (whether words, numbers or figures) and regardless
of the way the test is administered (in written or oral form, to an
individual or to a group). Tests of specific mental abilities do
measure those abilities, but they all reflect g to varying degrees as
well. Hence, the g factor can be extracted from scores on any diverse
battery of tests.
Conversely, because every mental test is "contaminated" by the
effects of specific mental skills, no single test measures only g.
Even the scores from IQ tests--which usually combine about a dozen
subtests of specific cognitive skills--contain some "impurities" that
reflect those narrower skills. For most purposes, these impurities
make no practical difference, and g and IQ can be used
interchangeably. But if they need to, intelligence researchers can
statistically separate the g component of IQ. The ability to isolate
g has revolutionized research on general intelligence, because it has
allowed investigators to show that the predictive value of mental
tests derives almost entirely from this global factor rather than
from the more specific aptitudes measured by intelligence tests.
In addition to quantifying individual differences, tests of mental
abilities have also offered insight into the meaning of intelligence
in everyday life. Some tests and test items are known to correlate
better with g than others do. In these items the "active ingredient"
that demands the exercise of g seems to be complexity. More complex
tasks require more mental manipulation, and this manipulation of
information--discerning similarities and inconsistencies, drawing
inferences, grasping new concepts and so on--constitutes intelligence
in action. Indeed, intelligence can best be described as the ability
to deal with cognitive complexity.
This description coincides well with lay perceptions of intelligence.
The g factor is especially important in just the kind of behaviors
that people usually associate with "smarts": reasoning, problem
solving, abstract thinking, quick learning. And whereas g itself
describes mental aptitude rather than accumulated knowledge, a
person's store of knowledge tends to correspond with his or her g
level, probably because that accumulation represents a previous
adeptness in learning and in understanding new information. The g
factor is also the one attribute that best distinguishes among
persons considered gifted, average or retarded.
Several decades of factor-analytic research on mental tests have
confirmed a hierarchical model of mental abilities. The evidence,
summarized most effectively in Carroll's 1993 book, Human Cognitive
Abilities, puts g at the apex in this model, with more specific
aptitudes arrayed at successively lower levels: the so-called group
factors, such as verbal ability, mathematical reasoning, spatial
visualization and memory, are just below g, and below these are
skills that are more dependent on knowledge or experience, such as
the principles and practices of a particular job or profession.
Some researchers use the term "multiple intelligences" to label these
sets of narrow capabilities and achievements. Psychologist Howard
Gardner of Harvard University, for example, has postulated that eight
relatively autonomous "intelligences" are exhibited in different
domains of achievement. He does not dispute the existence of g but
treats it as a specific factor relevant chiefly to academic
achievement and to situations that resemble those of school. Gardner
does not believe that tests can fruitfully measure his proposed
intelligences; without tests, no one can at present determine whether
the intelligences are indeed independent of g (or each other).
Furthermore, it is not clear to what extent Gardner's intelligences
tap personality traits or motor skills rather than mental aptitudes.
Other forms of intelligence have been proposed; among them, emotional
intelligence and practical intelligence are perhaps the best known.
They are probably amalgams either of intellect and personality or of
intellect and informal experience in specific job or life settings,
respectively. Practical intelligence like "street smarts," for
example, seems to consist of the localized knowledge and know-how
developed with untutored experience in particular everyday settings
and activities--the so-called school of hard knocks. In contrast,
general intelligence is not a form of achievement, whether local or
renowned. Instead the g factor regulates the rate of learning: it
greatly affects the rate of return in knowledge to instruction and
experience but cannot substitute for either.
The Biology of g
Some critics of intelligence research maintain that the notion of
general intelligence is illusory: that no such global mental capacity
exists and that apparent "intelligence" is really just a by-product
of one's opportunities to learn skills and information valued in a
particular cultural context. True, the concept of intelligence and
the way in which individuals are ranked according to this criterion
could be social artifacts. But the fact that g is not specific to any
particular domain of knowledge or mental skill suggests that g is
independent of cultural content, including beliefs about what
intelligence is. And tests of different social groups reveal the same
continuum of general intelligence. This observation suggests either
that cultures do not construct g or that they construct the same g.
Both conclusions undercut the social artifact theory of intelligence.
Moreover, research on the physiology and genetics of g has uncovered
biological correlates of this psychological phenomenon. In the past
decade, studies by teams of researchers in North America and Europe
have linked several attributes of the brain to general intelligence.
After taking into account gender and physical stature, brain size as
determined by magnetic resonance imaging is moderately correlated
with IQ (about 0.4 on a scale of 0 to 1). So is the speed of nerve
conduction. The brains of bright people also use less energy during
problem solving than do those of their less able peers. And various
qualities of brain waves correlate strongly (about 0.5 to 0.7) with
IQ: the brain waves of individuals with higher IQs, for example,
respond more promptly and consistently to simple sensory stimuli such
as audible clicks. These observations have led some investigators to
posit that differences in g result from differences in the speed and
efficiency of neural processing. If this theory is true,
environmental conditions could influence g by modifying brain
physiology in some manner.
Studies of so-called elementary cognitive tasks (ECTs), conducted by
Jensen and others, are bridging the gap between the psychological and
the physiological aspects of g. These mental tasks have no obvious
intellectual content and are so simple that adults and most children
can do them accurately in less than a second. In the most basic
reaction-time tests, for example, the subject must react when a light
goes on by lifting her index finger off a home button and immediately
depressing a response button. Two measurements are taken: the number
of milliseconds between the illumination of the light and the
subject's release of the home button, which is called decision time,
and the number of milliseconds between the subject's release of the
home button and pressing of the response button, which is called
movement time.
In this task, movement time seems independent of intelligence, but
the decision times of higher-IQ subjects are slightly faster than
those of people with lower IQs. As the tasks are made more complex,
correlations between average decision times and IQ increase. These
results further support the notion that intelligence equips
individuals to deal with complexity and that its influence is greater
in complex tasks than in simple ones.
The ECT-IQ correlations are comparable for all IQ levels, ages,
genders and racial-ethnic groups tested. Moreover, studies by Philip
A. Vernon of the University of Western Ontario and others have shown
that the ECT-IQ overlap results almost entirely from the common g
factor in both measures. Reaction times do not reflect differences in
motivation or strategy or the tendency of some individuals to rush
through tests and daily tasks--that penchant is a personality trait.
They actually seem to measure the speed with which the brain
apprehends, integrates and evaluates information. Research on ECTs
and brain physiology has not yet identified the biological
determinants of this processing speed. These studies do suggest,
however, that g is as reliable and global a phenomenon at the neural
level as it is at the level of the complex information processing
required by IQ tests and everyday life.
The existence of biological correlates of intelligence does not
necessarily mean that intelligence is dictated by genes. Decades of
genetics research have shown, however, that people are born with
different hereditary potentials for intelligence and that these
genetic endowments are responsible for much of the variation in
mental ability among individuals. Last spring an international team
of scientists headed by Robert Plomin of the Institute of Psychiatry
in London announced the discovery of the first gene linked to
intelligence. Of course, genes have their effects only in interaction
with environments, partly by enhancing an individual's exposure or
sensitivity to formative experiences. Differences in general
intelligence, whether measured as IQ or, more accurately, as g are
both genetic and environmental in origin--just as are all other
psychological traits and attitudes studied so far, including
personality, vocational interests and societal attitudes. This is old
news among the experts. The experts have, however, been startled by
more recent discoveries.
One is that the heritability of IQ rises with age--that is to say,
the extent to which genetics accounts for differences in IQ among
individuals increases as people get older. Studies comparing
identical and fraternal twins, published in the past decade by a
group led by Thomas J. Bouchard, Jr., of the University of Minnesota
and other scholars, show that about 40 percent of IQ differences
among preschoolers stems from genetic differences but that
heritability rises to 60 percent by adolescence and to 80 percent by
late adulthood. With age, differences among individuals in their
developed intelligence come to mirror more closely their genetic
differences. It appears that the effects of environment on
intelligence fade rather than grow with time. In hindsight, perhaps
this should have come as no surprise. Young children have the
circumstances of their lives imposed on them by parents, schools and
other agents of society, but as people get older they become more
independent and tend to seek out the life niches that are most
congenial to their genetic proclivities.
A second big surprise for intelligence experts was the discovery that
environments shared by siblings have little to do with IQ. Many
people still mistakenly believe that social, psychological and
economic differences among families create lasting and marked
differences in IQ. Behavioral geneticists refer to such environmental
effects as "shared" because they are common to siblings who grow up
together. Research has shown that although shared environments do
have a modest influence on IQ in childhood, their effects dissipate
by adolescence. The IQs of adopted children, for example, lose all
resemblance to those of their adoptive family members and become more
like the IQs of the biological parents they have never known. Such
findings suggest that siblings either do not share influential
aspects of the rearing environment or do not experience them in the
same way. Much behavioral genetics research currently focuses on the
still mysterious processes by which environments make members of a
household less alike.
g on the Job
Although the evidence of genetic and physiological correlates of g
argues powerfully for the existence of global intelligence, it has
not quelled the critics of intelligence testing. These skeptics argue
that even if such a global entity exists, it has no intrinsic
functional value and becomes important only to the extent that people
treat it as such: for example, by using IQ scores to sort, label and
assign students and employees. Such concerns over the proper use of
mental tests have prompted a great deal of research in recent
decades. This research shows that although IQ tests can indeed be
misused, they measure a capability that does in fact affect many
kinds of performance and many life outcomes, independent of the
tests' interpretations or applications. Moreover, the research shows
that intelligence tests measure the capability equally well for all
native-born English-speaking groups in the U.S.
If we consider that intelligence manifests itself in everyday life as
the ability to deal with complexity, then it is easy to see why it
has great functional or practical importance. Children, for example,
are regularly exposed to complex tasks once they begin school.
Schooling requires above all that students learn, solve problems and
think abstractly. That IQ is quite a good predictor of differences in
educational achievement is therefore not surprising. When scores on
both IQ and standardized achievement tests in different subjects are
averaged over several years, the two averages correlate as highly as
different IQ tests from the same individual do. High-ability students
also master material at many times the rate of their low-ability
peers. Many investigations have helped quantify this discrepancy. For
example, a 1969 study done for the U.S. Army by the Human Resources
Research Office found that enlistees in the bottom fifth of the
ability distribution required two to six times as many teaching
trials and prompts as did their higher-ability peers to attain
minimal proficiency in rifle assembly, monitoring signals, combat
plotting and other basic military tasks. Similarly, in school
settings the ratio of learning rates between "fast" and "slow"
students is typically five to one.
The scholarly content of many IQ tests and their strong correlations
with educational success can give the impression that g is only a
narrow academic ability. But general mental ability also predicts job
performance, and in more complex jobs it does so better than any
other single personal trait, including education and experience. The
army's Project A, a seven-year study conducted in the 1980s to
improve the recruitment and training process, found that general
mental ability correlated strongly with both technical proficiency
and soldiering in the nine specialties studied, among them infantry,
military police and medical specialist. Research in the civilian
sector has revealed the same pattern. Furthermore, although the
addition of personality traits such as conscientiousness can help
hone the prediction of job performance, the inclusion of specific
mental aptitudes such as verbal fluency or mathematical skill rarely
does. The predictive value of mental tests in the work arena stems
almost entirely from their measurement of g, and that value rises
with the complexity and prestige level of the job.
Half a century of military and civilian research has converged to
draw a portrait of occupational opportunity along the IQ continuum.
Individuals in the top 5 percent of the adult IQ distribution (above
IQ 125) can essentially train themselves, and few occupations are
beyond their reach mentally. Persons of average IQ (between 90 and
110) are not competitive for most professional and executive-level
work but are easily trained for the bulk of jobs in the American
economy. In contrast, adults in the bottom 5 percent of the IQ
distribution (below 75) are very difficult to train and are not
competitive for any occupation on the basis of ability. Serious
problems in training low-IQ military recruits during World War II led
Congress to ban enlistment from the lowest 10 percent (below 80) of
the population, and no civilian occupation in modern economies
routinely recruits its workers from that range. Current military
enlistment standards exclude any individual whose IQ is below about
85.
The importance of g in job performance, as in schooling, is related
to complexity. Occupations differ considerably in the complexity of
their demands, and as that complexity rises, higher g levels become a
bigger asset and lower g levels a bigger handicap. Similarly,
everyday tasks and environments also differ significantly in their
cognitive complexity. The degree to which a person's g level will
come to bear on daily life depends on how much novelty and ambiguity
that person's everyday tasks and surroundings present and how much
continual learning, judgment and decision making they require. As
gamblers, employers and bankers know, even marginal differences in
rates of return will yield big gains--or losses--over time. Hence,
even small differences in g among people can exert large, cumulative
influences across social and economic life.
In my own work, I have tried to synthesize the many lines of research
that document the influence of IQ on life outcomes. As the
illustration shows, the odds of various kinds of achievement and
social pathology change systematically across the IQ continuum, from
borderline mentally retarded (below 70) to intellectually gifted
(above 130). Even in comparisons of those of somewhat below average
(between 76 and 90) and somewhat above average (between 111 and 125)
IQs, the odds for outcomes having social consequence are stacked
against the less able. Young men somewhat below average in general
mental ability, for example, are more likely to be unemployed than
men somewhat above average. The lower-IQ woman is four times more
likely to bear illegitimate children than the higher-IQ woman; among
mothers, she is eight times more likely to become a chronic welfare
recipient. People somewhat below average are 88 times more likely to
drop out of high school, seven times more likely to be jailed and
five times more likely as adults to live in poverty than people of
somewhat above-average IQ. Below-average individuals are 50 percent
more likely to be divorced than those in the above-average category.
These odds diverge even more sharply for people with bigger gaps in
IQ, and the mechanisms by which IQ creates this divergence are not
yet clearly understood. But no other single trait or circumstance yet
studied is so deeply implicated in the nexus of bad social
outcomes--poverty, welfare, illegitimacy and educational
failure--that entraps many low-IQ individuals and families. Even the
effects of family background pale in comparison with the influence of
IQ. As shown most recently by Charles Murray of the American
Enterprise Institute in Washington, D.C., the divergence in many
outcomes associated with IQ level is almost as wide among siblings
from the same household as it is for strangers of comparable IQ
levels. And siblings differ a lot in IQ--on average, by 12 points,
compared with 17 for random strangers.
An IQ of 75 is perhaps the most important threshold in modern life.
At that level, a person's chances of mastering the elementary school
curriculum are only 50-50, and he or she will have a hard time
functioning independently without considerable social support.
Individuals and families who are only somewhat below average in IQ
face risks of social pathology that, while lower, are still
significant enough to jeopardize their well-being. High-IQ
individuals may lack the resolve, character or good fortune to
capitalize on their intellectual capabilities, but socioeconomic
success in the postindustrial information age is theirs to lose.
What Is versus What Could Be
The foregoing findings on g's effects have been drawn from studies
conducted under a limited range of circumstances--namely, the social,
economic and political conditions prevailing now and in recent
decades in developed countries that allow considerable personal
freedom. It is not clear whether these findings apply to populations
around the world, to the extremely advantaged and disadvantaged in
the developing world or, for that matter, to people living under
restrictive political regimes. No one knows what research under
different circumstances, in different eras or with different
populations might reveal.
But we do know that, wherever freedom and technology advance, life is
an uphill battle for people who are below average in proficiency at
learning, solving problems and mastering complexity. We also know
that the trajectories of mental development are not easily deflected.
Individual IQ levels tend to remain unchanged from adolescence
onward, and despite strenuous efforts over the past half a century,
attempts to raise g permanently through adoption or educational means
have failed. If there is a reliable, ethical way to raise or equalize
levels of g, no one has found it.
Some investigators have suggested that biological interventions, such
as dietary supplements of vitamins, may be more effective than
educational ones in raising g levels. This approach is based in part
on the assumption that improved nutrition has caused the puzzling
rise in average levels of both IQ and height in the developed world
during this century. Scientists are still hotly debating whether the
gains in IQ actually reflect a rise in g or are caused instead by
changes in less critical, specific mental skills. Whatever the truth
may be, the differences in mental ability among individuals remain,
and the conflict between equal opportunity and equal outcome
persists. Only by accepting these hard truths about intelligence will
society find humane solutions to the problems posed by the variations
in general mental ability.
Related Links
IQ Tests on the WWW: Web Directory
Intelligence and Personality Assessment: A Study Guide by Jon Potter
IQ: A Structure for Understanding by Timothy Bates, Macquarie
University Sydney
Great Ideas in Personality -- Intelligence by G. Scott Acton,
Northwestern University
Intelligence and IQ: Book reviews, commentaries and links to other
Net resources.
The Author
LINDA S. GOTTFREDSON is professor of educational studies at the
University of Delaware, where she has been since 1986, and co-directs
the Delaware-Johns Hopkins Project for the Study of Intelligence and
Society. She trained as a sociologist, and her earliest work focused
on career development. "I wasn't interested in intelligence per se,"
Gottfredson says. "But it suffused everything I was studying in my
attempts to understand who was getting ahead." This "discovery of the
obvious," as she puts it, became the focus of her research. In the
mid-1980s, while at Johns Hopkins University, she published several
influential articles describing how intelligence shapes vocational
choice and self-perception. Gottfredson also organized the 1994
treatise "Mainstream Science on Intelligence," an editorial with more
than 50 signatories that first appeared in the Wall Street Journal in
response to the controversy surrounding publication of The Bell
Curve. Gottfredson is the mother of identical twins--a "mere
coincidence," she says, "that's always made me think more about the
nature and nurture of intelligence." The girls, now 16, follow
Gottfredson's Peace Corps experience of the 1970s by joining her each
summer for volunteer construction work in the villages of Nicaragua.
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