|
 In
1905, Alfred Binet and Theodore Simon succeeded in creating a test that
would distinguish children with behavior problems from children who were
mentally retarded. The idea was to prevent children in France who had
behavior problems from being consigned to the dust heap that in those
days constituted the classrooms for the mentally retarded. The test proved
successful in predicting academic performance beyond that of just those
children at the lower end of the ability spectrum, and a variant of Binet’s
test, the Stanford-Binet, soon came to figure prominently in the landscape
of American schooling. Eventually, the Stanford-Binet was joined by other
tests, including individual measures such as the Wechsler series, and
group measures such as the Otis tests.
So
successful were these tests that Edward Boring, a Harvard psychologist
in the 1920s, proposed that intelligence is nothing more than what tests
of intelligence measure. Some might dismiss Boring’s definition as
trivial or circular, but it reflects a major issue here in the United
States and abroad about the nature and measurement of intelligence. To
this day, many psychiatrists as well as psychologists view intelligence
as essentially what the tests measure.
Increasingly
solid evidence is emerging that what psychological tests measure is only
a part of the entire portrait of what intelligence is. Over the next several
months, aspects of the nature of intelligence and the contribution of
genetic factors to intelligence will be reviewed in this column.
Investigators have studied implicit, or folk, theories
of intelligence around the world. People’s intuitive concepts of
intelligence are much broader than the conceptions represented by the
tests. A number of studies have asked lay people what they understand
intelligence to be. Their responses have included factors such as practical
problem-solving ability, verbal ability, and social competence. Although
verbal ability is carefully measured by existing tests, social competence
is generally not measured at all.
Conceptualizations
of intelligence vary by ethnic group. In a study of various groups in
California, for example, Latino parents emphasized social competence skills
in their definitions of intelligence whereas Asian and Anglo parents emphasized
cognitive competence skills. Teachers’ conceptions of intelligence
corresponded more to that of the Asian and Anglo parents. Not surprisingly,
children in these groups did better in school, perhaps in part because
of the match between their socialization and the expectations of the school.
Outside
the United States, the departures from the test-based notion are even
greater. In a study conducted in Taiwan, intelligence embraced not only
conventional cognitive abilities, but also interpersonal competence (understanding
of others), intrapersonal competence (understanding of self), intellectual
self-assertion (knowing when to show one’s intelligence), and intellectual
self-effacement (knowing when not to show one’s intelligence). (Fig.
1)
But
implicit theories do not tell the whole story. Performance-based definitions
of intelligence exist as well. At least 2 kinds of abilities appear to
be relatively distinct from the kinds of abilities measured by conventional
intelligence tests: creative abilities and practical abilities. In one
series of studies on creative intellectual abilities, individuals were
asked to write stories with unusual titles such as “2985,” to
draw artistic compositions on unusual topics such as “The earth from
an insect’s point of view,” to create advertisements for boring
products such as a brand of “bow ties,” or to suggest solutions
to problems such as that of how we would recognize extraterrestrial aliens
among us seeking to escape detection. Performance on tasks such as these
proved to be only weakly to moderately correlated with scores on conventional
tests of intelligence.
There
is even more evidence for the relative independence of practical intellectual
abilities from IQ and related measures. Practical intellectual abilities
reflect the ability to solve commonsense problems a person encounters
in the world of work. In multiple studies of business managers, academic
psychologists, sales people, teachers, and military leaders, scores on
tests of practical intelligence do not correlate well with IQ. Nonetheless,
practical intelligence predicts job performance as well as or better than
IQ. In a study of children in Kenya, a test of practical intelligence
involved children’s using knowledge they had acquired on how to use
natural herbal medicines to fight infections. In Kenya, this knowledge
is highly adaptive. Significant negative correlations were found with
conventional kinds of ability measures.
In
another set of studies, a test for high school students was developed
that measured traditional analytical abilities of the kinds found on conventional
intelligence tests, but also tests of creative and practical abilities.
This battery used both multiple-choice items and essay questions in the
verbal, quantitative, and figural domains. Analytical, creative, and practical
abilities were found to be relatively uncorrelated. The general (“g”)
factor so prevalent in conventional tests accounted for little of the
variance in the results. Apparently, this factor appears only when the
tests measure a fairly narrow range of abilities.
In
summary, the evidence suggests there is more to intelligence than IQ.
Creative and practical abilities matter as well as the more conventional
analytical abilities. These abilities are relatively independent of analytical
abilities, but they are measured minimally or not at all by conventional
tests. We need to develop new, expanded tests to assess a broader range
of intellectual abilities. Indeed, lack of adequate psychometric tools
assessing other than g-related intellectual abilities is one of the main
reasons why the conventional view of intelligence dominates the field.
The
field of behavioral genetics of intelligence uses the old, g-related view
of IQ. Virtually none of the new developments in the general theory of
intelligence have penetrated the field. The argument here is that any
instrument used in behavioral-genetic studies needs to be psychometrically
solid, and there is nothing in the field that even approaches the psychometric
properties of g-based tests. Correspondingly, behavioral geneticists still
conceptualize the domain of cognitive abilities only as a g-championed
hierarchy of abilities.
Given
the absolute power of the psychometric theory of intelligence in behavioral-genetic
studies of intelligence, it is not surprising that such studies support
the g view of intelligence. It is remarkable, however, that since the
consensus was reached a number of years ago that genetic variability explains
about 50% of observed individual differences in general cognitive ability
(with an upper boundary of about 80% obtained through direct estimates
of heritability using relatives reared apart and a lower boundary of about
40% obtained through indirect estimates of heritability using relatives
reared together), behavioral-genetic models have not changed to accommodate
the new evidence accumulated in psychological theories of intelligence.
Even
though the importance of genes in the development of individual differences
in IQ has been unequivocally established, these influences account for
only half of the variability. Moreover, much debate was generated by the
publication of The Bell Curve, which unequivocally supported the g view
and the argument that g is subject to substantial genetic impact. It is
clear that the issues of the definition of intelligence, genetic influences,
and validity and reliability of modern intelligence tests remain to be
discussed.
To
date, behavioral-genetic research addresses exclusively the etiology of
g-based abilities. Whereas other areas of psychology have appreciated
the diversity of human abilities, the field of behavioral genetics remains
a dedicated soldier in the g-empire. Although the findings about the heritability
of g-based abilities are reliable and conclusive, g appears to be only
one of the letters of the alphabet of human abilities.
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