[Paleopsych] Wilson Q.: Schools and the g Factor by Linda S. Gottfredson
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Schools and the g Factor by Linda S. Gottfredson
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In the world of the American public school, few subjects are more
controversial than intelligence. If theres a tension in American
society between the ideal of equality and the pursuit of meritocracy,
that tension escalates into the equivalent of a migraine headache in
the schools. Called upon to produce young people fully prepared for
citizenship and ready to meet the competitive challenges of the modern
economy, the schools are also seen, at the same time, as the nations
last best hope to level the playing field and ensure equal opportunity
for all. In no American institution is the egalitarian strain of the
American creed stronger. And the very notion that school performance
is strongly influenced by general intelligencea quality partly
inbornseems to contradict this deeply held ideal of equality.
During the past few decades, the word intelligence has been attached
to an increasing number of different forms of competence and
accomplishmentemotional intelligence, football intelligence, and so
on. Researchers in the field, however, have largely abandoned the
term, together with their old debates over what sorts of abilities
should and should not be classified as part of intelligence. Helped by
the advent of new technologies for researching the brain, they have
increasingly turned their attention to a century-old concept of a
single overarching mental power. They call it simply g, which is short
for the general mental ability factor. The g factor is a universal and
reliably measured distinction among humans in their ability to learn,
reason, and solve problems. It corresponds to what most people mean
when they describe some individuals as smarter than others, and its
well measured by IQ (intelligence quotient) tests, which assess
high-level mental skills such as the ability to draw inferences, see
similarities and differences, and process complex information of
virtually any kind. Understanding gs biological basis in the brain is
the new frontier in intelligence research today.
The g factor was discovered by the first mental testers, who found
that people who scored well on one type of mental test tended to score
well on all of them. Regardless of their contents (words, numbers,
pictures, shapes), how they are administered (individually or in
groups; orally, in writing, or pantomimed), or what theyre intended to
measure (vocabulary, mathematical reasoning, spatial ability), all
mental tests measure mostly the same thing. This common factor, g, can
be distilled from scores on any broad set of cognitive tests, and it
takes the same form among individuals of every age, race, sex, and
nation yet studied. In other words, the g factor exists independently
of schooling, paper-and-pencil tests, and culture.
Though there has been intense controversy about IQ tests over the
years, psychologists continue to see them as valid and useful gauges
of student potential. No longer routinely administered to whole school
populationsachievement tests are much better suited to tasks such as
grouping students for instructionthey are widely used by school
psychologists in individual assessments to determine, for example,
whether a child who is having difficulties in school has a learning
disability or some other problem. As a practical matter, all good
standardized tests of IQ and achievement end up ranking students in
much the same way because g is the major predictor of academic
achievement.
During the 1960s and 1970s, educators launched several ambitious
efforts to raise the IQs of disadvantaged youngsters in experimental
preschools. The results were discouraging: Even when it was possible
to raise the IQs of young children, the gains never translated into
comparable gains on achievement tests, and the IQ gains evaporated
soon after children left the programs. The disappointing results
helped fuel an attack by some researchers on the very idea of IQ and g
and also contributed to the rapturous reception for the theory of
multiple intelligences that emerged in the 1980s, notably in Howard
Gardners Frames of Mind (1983). To replace the idea of general
intelligence, Gardner, a developmental psychologist at Harvard
Universitys Graduate School of Education, proposed seven coequal
intelligences: linguistic, logical-mathematical, visual-spatial,
musical, bodily-kinesthetic, interpersonal, and intrapersonal (he
later added naturalist, to make eight).
Gardners theory offers a useful reminder that there are many human
abilities and forms of accomplishment, and it puts new labels on some
of the most common of them. Thus, good athletes have
bodily-kinesthetic intelligence, and self-help celebrities such as
Oprah Winfrey have intrapersonal intelligence. Gardner takes the
seemingly commonsensical notion that people meet the world in
different ways and elevates it into a comforting accolade: Everybody
is smart in some way.
In the classroom, the theory seems to give teachers a new language to
describe their perceptions of students and classroom life. Teacher
guidebooks such as Teaching and Learning through Multiple
Intelligences (1995) suggest using the eight intelligences as
different entry points for leading students into a single lesson. To
teach a unit about photosynthesis, for example, a teacher might have
all students read a description of photosynthesis to provide an entry
point for the linguistically intelligent, have the class compare
plants grown with and without sufficient light to reach children with
naturalist intelligence, engage the logical-mathematical students by
asking the class to prepare a timeline for the steps of
photosynthesis, require painting those steps to aid the
visually-spatially inclined, have students role-play the characters in
photosynthesis to help the bodily-kinesthetic childand so on, until
all eight intelligences have been accommodated.
Theres something very appealing about this scenario, but its unlikely
that students kept so busy walking through multiple doorways will have
much time to advance very far once they get through them. As one
biology teacher told me recently, the multiple intelligence approach
may allow students with special talents to express their understanding
in ways that are personally gratifying, but science is inherently
analytical, and understanding it ultimately requires the application
of strong reasoning and analysis skillsperiod.
However much we might wish that there were many distinct forms of
mental ability, a century of research has found none as widely useful
as g. Neither of the two major multiple intelligence theorists, Howard
Gardner and Yale Universitys Robert Sternberg, disputes the existence
of g, only its preeminence among mental abilities. There are, to be
sure, many different human mental abilities, but they are neither
independent of one another nor equally useful.
The past 100 years of research has yielded a body of knowledge that
virtually all those working in the field accept as valid, despite
their various perspectives and the controversies surrounding this
issue. Differences in IQ among young children can be traced in about
equal parts to differences in their genes and their environment. (A
special panel named by the American Psychological Association to
summarize the state of knowledge on intelligence in 1995 noted that
the lowest possible estimate of the genetic component is about 40
percent.) Genetic differences become a bigger source of intelligence
differences as children age. Behavior geneticists suspect the reason
is that as they achieve more independence, children are more able to
select and shape their environments, which then shape them. The power
of genes can be seen in the fact that identical twins reared apart are
more alike, after meeting in adulthood, in IQ, brain function,
personality, and many other traits and behaviors than fraternal twins
raised in the same home.
Genes probably work their influence by shaping various metabolic,
electrical, and structural features of the brain. For example, the
brains of people with higher IQs tend to have a relatively lower rate
of energy use (as measured by glucose metabolism) while solving
problems, and quicker and more complex brain waves in response to
simple perceptual stimuli such as lights and sounds. Researchers have
long debated whether people with higher IQs have bigger brains, and
the latest findings, based on studies with new brain-scan technology,
show that they do. Distinctions in g, or general intelligence, are
evidently as much a fact of nature as differences in height, blood
pressure, and the like.
A great deal of research also shows that g matters well beyond school.
In Who Gets Ahead? (1979), sociologist Christopher Jencks and his
colleagues reviewed many large studies and showed that an individuals
IQ predicts his occupational level and income in adulthood (as well as
years of schooling completed) better than his fathers education or
occupation does. The influence of g varies in different realms of
lifeschooling, work, parenthoodsimply because some are less
cognitively demanding than others. Some life outcomes are also shaped
more than others by such factors as ones noncognitive traits
(ambition, extraversion) and decisions that others make about the
individual (college admissions, hiring, pay raises). Yet the evidence
of gs pervasive and lasting impact is well documented, especially when
it comes to lifes more complex tasks. For example, personnel
psychologists Frank Schmidt and John Hunter reviewed thousands of
studies that were conducted over 85 years in many different companies,
government agencies, and military settings, and that used everything
from handwriting analysis to job tryouts to forecast job performance.
Their meta-analyses of these data showed that mental tests predict
on-the-job performance better than personality, integrity level,
experience, and education. In the Journal of Personality and Social
Psychology, I recently published a study showing that both IQ and
adult functional literacy correlate in the same pattern with a wide
variety of adult outcomes, including health and longevity (in part
because maintaining ones health requires learning and adaptation), all
regardless of social background. In that same journal, University of
Edinburgh psychologist-physician Ian Deary and his colleagues reported
on a study showing that each one-point increase in IQ when the study
participants were 11 years old predicted a one percent decrease in
mortality by age 50. If IQ is book smarts, it is clearly much more
besides.
Drawing a bead on exactly what g is and how it works remains a
difficult task, but specialists in mental testing now commonly agree
that g sits atop a hierarchy of mental abilities. Most of these
researchers have adopted the three-level hierarchy developed by
educational psychologist John B. Carroll in his monumental Human
Cognitive Abilities (1993). After statistically extracting the common
ability factors from more than 450 earlier studies in which multiple
tests had been administered to the same individuals, Carroll
classified all abilities into three levels.
At the highest level, Stratum III, Carroll found evidence of only one
ability: g. In Stratum II, he documented eight broad abilities
involving language, reasoning, spatial visualization, auditory
perception, memory, and cognitive speediness. Stratum I includes
relatively specific mental abilities, such as memory span and reading
comprehension.
All Stratum II aptitudes are highly correlated with one another. A
person with weak language ability, for example, is very unlikely to be
strongly endowed with another Stratum II ability, such as spatial
visualization. Tests of these abilities show that they are highly
correlated both with one another and with g. All consist primarily of
g plus a dose of some more specific ability. As Carroll puts it, the
Stratum II abilities are all different flavors of g. Despite many
attempts, nobody has ever succeeded in creating tests that measure
these abilities without simultaneously measuring mostly g.
Most IQ test batteries are composed of about a dozen subtests
(involving, for example, vocabulary, sentence completion, number
series, matrices, and similarities) of abilities near the Stratum I
level. A persons scores on each are added together to produce an IQ
score. But ones intuitive sense that the Stratum I abilities are the
building blocks of intelligence is incorrect. The basic element at
each level is g. A Stratum II ability is made up of g plus some more
specialized ability. A Stratum I ability is produced by adding an even
more specialized ability to this mix. Each lower stratum thus includes
increasingly numerous and more complex amalgams of skills that are
targeted to fewer and more specific kinds of tasks.
Researchers have drawn quite a clear picture of human mental
abilities. For instance, the technical manual for one widely used
test, the Stanford-Binet IV, shows that the Stratum I ability
vocabulary is about three parts g, plus two parts a special language
facility that makes its entrance at the Stratum II level, plus one
part a vocabulary-specific ability entering at Stratum I. Similarly,
the Stratum I ability memory for sentences is roughly two parts g, one
part each special verbal and memory abilities entering at Stratum II,
and one part an ability specific to Stratum I.
Carroll points out that four of Gardners intelligences (linguistic,
logical-mathematical, spatial, and musical) correspond to four Stratum
II abilities. They arent independent abilities, as Gardner asserts,
but rather are linked to one another and to g. Three of Gardners four
other intelligences fall largely outside the cognitive realm, while
the fourth (naturalist) is too diffuse to analyze. Gardners
intrapersonal and interpersonal intelligences seem to be matters
mostly of personality, while his bodily-kinesthetic intelligence
reflects mostly psychomotor strengths such as eye-hand coordination.
These are useful qualities, to be sure, and they can help a person get
by in the world, but they will not help that person apprehend the
world. For that you need g.
Because gifted children tend to have more jagged ability profiles than
children of average or below-average intelligencethink of the classic
math wiz who is not as dazzling in subjects such as history that
depend on verbal reasoningGardner can allow educators to draw the
inference that every child can be smart in some way. But the math wiz
will still have relatively strong verbal skills. Where theres notable
talent, theres always a high level of g. Gardner implicitly
acknowledges this when he concedes that all the individuals he names
as exemplars of his eight intelligences probably had IQs above 120
(the 90th percentile). His eight domains of achievement may enrich our
lives, but they do not represent independent faculties of mind or
alternate pathways to mastering school curricula, jobs, or everyday
tasks.
Gardners theory has been protected from direct contradiction by his
failure to develop any formal tests of his proposed intelligences. (He
believes that assessments should be more holistic.) None of the
assessments that schools currently use to identify students multiple
intelligences would satisfy the standards for testing jointly
promulgated by the three major professional organizations in the
field. Mindy Kornhaber, a Gardner collaborator now at the University
of Pennsylvania, evaluated three major methods for identifying gifted
students in terms of multiple intelligences and concluded in In the
Eyes of the Beholder (2004) that they are not technically strong
enough to withstand modest scrutiny. Among other problems, some use
checklists that seem to assess interests rather than abilities, and
none have clear enough procedures for raters to agree on who is gifted
or in what way.
In the education textbooks used to instruct tomorrows teachers,
however, one doesnt get any sense that ample evidence favors a single
broadly useful intelligence rather than multiple independent ones.
Textbooks written by educational psychologists tend to report the
facts about IQ with reasonable accuracy, but they systematically
minimize or muddy the measures relevance. For example, they will
report that IQ tests predict academic achievement quite well, but then
imply that this fact need not be taken seriously because, after all,
thats precisely what IQ tests were first developed to do. IQ, they
say, represents only a narrow academic ability, book smarts, and it
matters little outside school. All of this is often topped off with
the closing argument that IQ does not capture everything important
about the human mind and soulas if intelligence researchers have ever
said otherwise.
The presentation of facts may be muddied but the larger message is
clear: Multiple intelligence theories are the modern alternativethe
antidoteto outmoded unitary, narrow, and exclusionary theories of
ability. Textbooks create an aura of scientific superiority for the
new theories by substituting their advocates certitude for evidence,
and the absence of any pertinent research for readers to critique
leaves the claims pristine. Take, for example, Laurence Steinbergs
Adolescence (2002), a textbook assigned to future teachers at the
University of Delawares School of Education, where I am on the
faculty. Steinberg blithely asserts that even the best IQ tests used
today measure only a very specific type of intelligence, and that
there are ways of being equally intelligent as individuals who score
high on IQ testsbut intelligent in a different way.
Multiple intelligence theory gathers unto itself all good things.
Commonly accepted pedagogical principles that have no necessary
relation to multiple intelligence theorythat teachers should go beyond
rote learning, appreciate students strengths and weaknesses, use
different modes of presenting information, and believe that all
students can learnare described as if they were the hallmarks of the
multiple intelligence approach alone. The theorys proponents link
harmful, distasteful, and patently false beliefs with IQfor example,
that IQ is immutable, environments do not affect learning, some
children cannot learn, and IQ is a measure of human worth. Readers are
left with the impression that it is morally suspect to favor narrow
views of intelligence, which are elitist, and segregate or privilege
some students. For all their rhetoric about diversity, proponents of
multiple intelligence betray a deep uneasiness with difference.
The vogue for multiple intelligences is just one manifestation of an
attack on ability grouping and curriculum tracking in the schools that
has been underway for decades. Federal enthusiasm for programs for
gifted children, for example, spiked after the Soviet launch of
Sputnik in 1957, and then evaporated in the early 1960s. (Since that
decade, scores by Americas highest-performing students have fallen on
national tests such as the SAT and the Stanford Achievement Test.)
Access to advanced placement courses and programs for the gifted is
being opened up in the name of inclusion, and as a result, many
programs are sacrificing their rigor and distinctive curricula.
Grouping students by ability level in classes or in small groups
within classes offers the promise of differentiating instruction to
better fit diverse student-ability levels (though in reality that
promise is seldom fulfilled). As recently as the 1980s, between 80 and
90 percent of eighth and tenth graders were being taught in
ability-homogeneous classrooms. Twenty-two percent of seventh graders
were in homogeneous classes for all subjects, and 47 percent for some
subjects. About 90 percent of elementary schools at the time were
using within-class grouping for at least one subject, and 70 percent
were using between-class grouping. Im aware of no more recent surveys,
but observers agree that increasing numbers of schools are attempting
to eliminate grouping and tracking and also to mainstream both gifted
and special-education students into regular classrooms.
The effects of this trend, so cavalierly endorsed by those who
fantasize classrooms full of pluralistically smart students, are more
candidly described in textbooks for teaching instructional strategies.
The text we use at the University of Delaware, Looking in Classrooms
(2003), declares that educators thinking has progressively moved away
from policies of exclusion and homogeneous grouping toward an emphasis
on the value of diversity, policies of inclusion, and practices that
meet the needs of all students. But Looking in Classrooms is very
clear about the realities teachers face. It paints a sobering portrait
of the heterogeneous classes created by the demise of grouping,
tracking, and special classes for disabled or gifted students. Its
case example is a sixth-grade classroom with 26 students from varied
racial and ethnic backgrounds and family configurations. Three of the
students spoke little or no English, and one of them was legally
blind. Among the 23 who could be validly tested, the grade equivalents
for reading ranged along a breathtaking span from 2.3 to 10.5; two
students were gifted. Such large disparities are common in
heterogeneous junior-high classrooms. As Looking in Class-
rooms describes it, the teachers solution for orchestrating
appropriately different instruction of the same key ideas for her 26
highly diverse students calls for an effort that is nothing short of
heroic. Its as if teachers today must not only work in a one-room
schoolhouse but also individualize instruction for all their charges
so that all can master the same (trimmed down) curriculum in lockstep.
Degrouping, which is meant to prevent the social distinctions that
arise when students are segregated by ability level, can create even
bigger distinctions. Placing the intellectually unequal in proximity
forces students to observe their differences in capability more
directly. It is hard to miss the fact that some students typically
learn two to five times faster than others, or that some are reading
difficult books while others struggle with simple ones. All teacher
textbooks therefore emphasize, at least implicitly, that a teachers
first concern in mixed-ability classrooms must be to ensure that
students perceive each other as social equals.
Looking in Classrooms reviews research on some of the familiar
techniques for putting this into practice, such as cooperative
learning and peer tutoring. These are strategies for having students
interact across ability lines in ways that enhance the performance of
low-ability students without stigmatizing them for their lesser
achievement. Proponents cite experimental studies showing that these
methods do indeed improve performance among low-achieving students,
while somewhat enhancing, or at least not impairing, performance among
more-able students. Only the fine print reveals that the experiments
deal just with basic skills, not with higher levels of understanding.
Like other textbooks, Looking in Classrooms mentions highly able
students only when discussing how to lean on them for tutoring of
their less-able classmates.
In reality, these instructional strategies for mixed-ability classes
preclude precisely what helps the more-able students most:
accelerating their curriculum, allowing them to interact with their
intellectual peers, and making them work hard. Accelerated and
compacted curricula can double the speed at which highly able students
advance, but such differential treatment is decried as elitist and
exclusionary. As targeted instruction for gifted children is reduced
in the public schools, their parents must increasingly rely on
opportunities outside regular school settings. Summer programs for
talented youngsters at universities, for example, are routinely able
to advance the top one percent of 13-year-olds one full year in
biology, chemistry, physics, Latin, or math in the space of only three
weeks.
Tracking and grouping persist in American schools despite the strong
pressure for their elimination. Math and science teachers remain
strong advocates of tracking, and many parents lobby hard for the
programs they think their children need. Theres also significant
pressure from above: College and university admissions offices want to
be able to identify students who have taken demanding courses. And
theres the inescapable reality that its very difficult to produce good
results for any students when they are placed in heterogeneous
classes. As James A. Kulik of the University of Michigan reported in
the Handbook of Gifted Education (2003), On the basis of site visits,
experts have concluded that untracking brings no guarantee of
high-quality instruction for everyone but may instead lead all to a
common level of educational mediocrity.
Multiple intelligence theory is only the latest rationale for acting
as if most children dont differ much in learning ability. An older
approach, still widely embraced, is to accept IQ as a concept but act
as if differences in IQ dont make much difference in the classroom.
Education textbooks and journals in this vein speak only of
exceptional versus regular students. So-called regular students are
those who score between the upper threshold for mental retardation (IQ
70) and the lower threshold for giftedness (IQ 130). That continuum
includes 95 percent of students. A closer look at differences in
intellectual functioning across the 60-point range illustrates how
different educability actually is, even among the supposedly average.
For example, individuals with IQs between 70 and 80 (but still above
the threshold for mild retardation) require instruction that is highly
structured, detailed, concrete, well sequenced, omits no intermediate
steps, and links to what the individuals already know. They often need
one-to-one supervision and hands-on practice to learn even simple
procedures. As specialists in adult education explain, the material to
be learned must be stripped of all nonessentials, including
theoretical principles, and require only simple inferences. Any
information, written or spoken, must be presented in small pieces with
clear introductions and simple vocabulary. Because people with IQs
below 80 (the 10th percentile) are difficult to train, federal law
bars their induction into the military.
Successively higher IQs are associated with better odds of learning
readily from more demanding forms of instruction, learning more
independently, and mastering increasingly abstract and multifaceted
material. Individuals of average IQ (100) can master relatively large
bodies of written and spoken knowledge and procedure, especially when
it is presented to them in an organized manner that allows them
practice and provides feedback. By IQ 120, individuals are more
self-instructing and better able to develop and organize knowledge on
their own. The complete instruction that is most helpful for low-g
learners is dysfunctional for these high-g individuals. The latter
easily fill in gaps in instruction on their own and benefit most from
abstract, self-directed, incomplete instruction that allows them to
assemble new knowledge and reassemble old knowledge in idiosyncratic
ways. But such forms of instruction are dysfunctional for low-g
learners, who are more likely to be confused than stimulated by its
incompleteness, abstractness, and requirements for self-direction.
As any teacher will attest, many other things besides g-level affect
childrens learningillness, incentives, peer pressure,
conscientiousness, parental support, familiarity with the language of
instruction, and more. For these and other reasons, high g does not
guarantee successor low g guarantee failure. Theres no question,
however, that higher levels of g constitute a constant tailwind and
lower levels a persistent headwind in cognitively demanding settings
such as schools. Perhaps most important, g level affects what students
are likely to learn with a reasonable expenditure of time and effort.
Textbooks on instructional strategies rightly treat time as a precious
commodity to be jealously guarded and wisely spent, and they note that
slow students often need much more of it than others to learn the same
material. Instruction must therefore be more tightly focused on what
is most essential for them to learn.
Although slow learners cannot be turned into fast learners, all
students could learn much more than they now do. Students learn best
and reap the most gratification for their efforts when instruction is
targeted to their cognitive needs. Good targeting is all too rare,
even in schools with ability grouping and curriculum tracking. As
Looking in Classrooms laments, such adaptive instruction is regularly
attacked as discriminatory because it means treating students
differently. Its critics would rather give all students access to the
high-status curricula and self-directed, constructivist learning
activities that benefit bright students. But that path is far more
likely to harm than to help these students, robbing them of the
motivation to learn, depriving them of their full potential, and
hampering their prospects in a world that increasingly requires (and
rewards) well-educated people. Depriving faster learners of curricula
that allow them to make the most of their abilities is likewise an
injustice to them and to the society that stands to benefit from their
eventual contributions. By denying the difficulties in accommodating
intellectual difference, multiple intelligence theories may do little
more than squander scarce learning time and significant opportunities
for improvements in the quality of American schooling.
The substantial heritability of intelligence has been a source of
great controversyalbeit only outside the community of researchers who
study the subject. But that element of heritability provides the very
hope it is often said to obliterate. While it frustrates our efforts
to raise IQ, it also greatly limits the harm that poor environments
can do. Research roundly affirms what experience suggests: People with
higher IQs have a remarkable ability to make their way out of even the
most dire environments. This protection, along with the
little-appreciated fact that the laws of genetics ensure that parents
and children will tend to differ substantially in IQ, guarantees that
talent will emerge from even the worst of environments, in turn
ensuring considerable social mobility in any free society. Its not
only the distribution of IQ that is helped by the laws of genetics.
The mixture of genes from two parents creates traits in children that
neither parent has. Heritability thus provides a very broad guarantee
of difference and variety we would not have in a world where
environment was all, a world that might leave humans free not only to
create an egalitarian paradise but to forge the ultimate caste society
of rich and poor.
It has always been the task of Americas public schools to facilitate
social mobility, and, historically, they have performed the job well.
They should now turn their attention to optimizing the development of
all children. For that to happen, well have to acknowledge that God or
nature did not make us all equal intellectually. By embracing rather
than rejecting the scientific knowledge about g, educators can develop
curricula and classroom techniques that well serve the nations
cognitively diverse students.
Linda S. Gottfredson is a professor of education at the University of
Delaware and an affiliated faculty member in its University Honors
Program. She is the author of many articles on the role of
intelligence differences in school, work, and everyday life, and the
editor of several special journal issues on these topics, including an
issue of Intelligence, Intelligence and Social Policy (1997).
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