C
harles Murray and R.J Herrnstein (now
deceased) knew very well that the mere mention of race in The Bell Curve:
Intelligence and Class Structure in American Life would expose their work
(and themselves) to severe criticism. They were not prepared, however, for
the verdict of "guilt by association" rendered by (among others) ABC News,
which likened The Bell Curve to the work of the "Professors of Hate"
profiled in the oft quoted Rolling Stone article of October 24. Nor were
they prepared to hear no fewer than three respected commentators on the
MacNeil Lehrer NewsHour of October 28 denounce the book as a "political
tract," rather than a scientific treatise, despite its strict conformance
with accepted guidelines for the conduct of scientific inquiry. Right or
wrong, The Bell Curve is hardly the compendium of neo-nazi pseudoscience
some make it out to be.
Despite the clarity of its exposition, the book's contents are only
partially accessible to technically unsophisticated readers, since the
claims made and the evidence adduced are both statistical in nature. The
claim is made, in particular, that intelligence is an effectively scalar
quantity, measurable by standard IQ tests administered (sometimes in as
little as 12 minutes) by trained examiners, and that scores so obtained
during the high school or even junior high school years are unexcelled
predictors of adult employment status and earning power.
The authors express great confidence in the abstract measure of "general
intelligence" proposed in 1904 by a former British Army officer named
Charles Spearman, using the then still new concept of a correlation
coefficient. As data from would-be intelligence tests began to accumulate,
Spearman noticed that people who did well on one such test tended to do well
on others, while those who did poorly on one tended to do poorly on all.
Even when two tests were purposely designed to measure radically different
cognitive skills, the correlation between scores remained positive. Although
the correlations varied considerably in strength from one pair of tests to
the next, they were (and continue to be) consistently positive. This
convinced Spearman that differences between one intelligence and another are
differences of degree, but not of kind, and motivated him to develop a
scalar measure (and call it "g", for general intelligence) to quantify such
differences. An analogy from the world of boxing might shed some light on
the nature of g. All the measurements included in the "tale of the tape"
before a prize fight of any consequence -- such as height, weight, and reach,
along with circumferences at the chest (expanded and normal), neck, waist,
thigh, wrist, ankle, fist, and bicep -- correlate positively with one
another, at least to the extent that heavyweights tend to be larger in each
dimension than middleweights, who tend to be larger in every way than
lightweights. In consequence, Spearman's algorithm can be employed to
determine an abstract scalar measure b of "boxer size." Perhaps the fight
game should replace its traditional weight classes with b-classes: Maybe
young fighters could be better protected from injury that way. That still
doesn't mean, however, that boxer size is a scalar quantity, or that the
differences between two boxers of equal b are unimportant.
Spearman's method applies equally well to measurements of intelligence and
boxer size and reveals no more about the one than about the other.
Nevertheless, Herrnstein and Murray cite an extensive literature purportedly
placing the essential correctness of Spearman's conclusions beyond
reasonable doubt. They also point out that the current tests have largely
been purged of the "cultural bias" once alleged to invalidate them:
Twenty-five years have passed since the appearance of the report that made
bias a sensitive issue (Arthur Jensen, 1969), and the problem never was as
grave as advertised, say Herrnstein and Murray, nor, given time and good
will, as hard to correct.
For these and other reasons, Herrnstein and Murray tend to ignore the
distinctions between g, IQ, and intelligence. Because others refuse to
concede that those distinctions are unimportant, however, the abbreviation "IQtelligence"
is used in place of "intelligence as measured by g" in the remainder of this
review. The extent to which intelligence and IQtelligence are one and the
same thing may never be known. Although g is easily measured, attempts to
define it and to observe it directly have never succeeded.
Because even the most efficient intelligence tests include many questions, a
high degree of "data compression" is undoubtedly possible without
significant information loss. The Educational Testing Service achieves it by
reporting just two scores (for verbal and quantitative abilities) on its oft
defamed SAT test and three (for verbal, quantitative, and analytical skills)
on its Graduate Record Examination. Both sets of scores are expressed on the
familiar SAT scale, with its standard deviation of 100 about a mean of 500.
Spearmanites further simplify the reporting process by combining scores from
the different segments of a given intelligence test into a weighted average
representing g, typically expressed on the IQ scale, where the standard
deviation is 15 about a mean score of 100. Herrnstein and Murray justify (in
part) their acceptance of g as a measure of intelligence by observing that
little, if any, of the predictive power of intelligence testing seems to be
lost by so doing. Although teenage IQ is not by itself a reliable predictor
of success in engineering and other quantitative curricula, it does seem to
predict adult employment status and earning power in today's increasingly
complex world.
The first of the four parts of The Bell Curve summarizes extensive evidence
indicating that IQtelligence is (at least statistically) predictive. Part II
explores the extent to which low IQ appears to predispose an individual
toward poverty, failure in school, unemployment, illness, injury in the
workplace, family problems, welfare dependency, and ineffective parenting,
or a life of crime, incivility, and poor citizenship. Although these and
other social ills have been studied extensively, IQ and its equivalents have
often been omitted from the list of potential explanators, seriously
compromising (at least in the opinion of Herrnstein and Murray) the validity
of the conclusions reached. They stress that "years in school" and "highest
degree earned" are inadequate proxies for IQtelligence. Part III digresses
on racial issues, and a short Part IV discusses conclusions and policy
prescriptions.
Resting as it does on the still controversial statistical technique known as
meta-analysis, the evidence with which the authors seek to establish the
correlation between teenage IQtelligence and adult status and earning power
demands scrutiny. In use since 1904, when Karl Pearson grouped data from the
British military to conclude that the then current practice of vaccination
against intestinal fever was ineffective, the technique did not become
commonplace until the 1980s. Today, meta-analysis is prominent in medical
research and is becoming more so in the social sciences, due in part to its
1992 endorsement by the National Research Council. It is designed to
illuminate the not uncommon situation in which scores or even hundreds of
costly studies of a given issue have already been made, by a host of
different investigators, using a variety of different approaches, without
achieving actionable consensus.
Meta-analysis represents an attempt to replace the blue ribbon committee
approach to building such consensus with something more scientific. The idea
is to treat the existing studies as data to which the tools of statistical
inference may be applied. Yet meta-analysis remains a controversial method
of inference which has sparked controversy in every field to which it has
been applied: Few investigators, it has been suggested [1], possesses the
statistical expertise to conduct and interpret meta-analysis.
That said, it does appear that postadolescent IQ has indeed become an
excellent predictor of adult "employment status" and/or earning power. The
authors of The Bell Curve point out, in summarizing the findings on which
that conclusion presently rests, that whereas the year 1900 found the top
10% of American IQs scattered almost uniformly throughout the workforce (if
not on the farms where half the population still lived, then in stores,
churches, factories, bicycle shops, and the like), the second millennium
will find them highly concentrated in science, medicine, the law, top
management, and a handful of other more or less prestigious occupations. As
the social and financial barriers that once restricted entry into the more
desirable occupations have fallen, members of what Herrnstein and Murray
term the "cognitive elite" have come to all but monopolize them.
Readers of The Bell Curve will, of necessity, learn much about this
cognitive elite. In addition to spending more years in school than most, and
receiving better grades, say the authors, members "watch far less television
than the average American. Their movie-going tends to be highly selective.
They seldom read the national tabloids that have the nation's highest
circulation figures or listen to the talk radio that has become a major form
of national communication for other parts of America." They are also, even
at an early age, more politically inclined than average. None of this means
that "the cognitive elite spend their lives at the ballet and reading
Proust. Theirs is not a high culture, but it is distinctive enough to set
them off from the rest of the country in many important ways."
Members tend, in particular, to live in virtual isolation from nonmembers.
As columnist Mickey Kaus puts it, "I entered a good Ivy League college in
1969. I doubt I've had a friend or regular social acquaintance since who
scored less than 1100 on his or her SAT boards." Isolated or not, members of
the cognitive elite tend to earn substantially more than other Americans.
The figure shown here, which appears on page 516 of The Bell Curve, provides
historical perspective. As shown in the figure, whereas median family income
rose rather steadily to a 1973 peak, then leveled off at a somewhat lower
level, the fraction of American families with income in excess of a hundred
thousand 1990 dollars has continued to climb (with some irregularities).
Their new-found riches, Herrnstein and Murray allege, tend to bring the
political interests of the cognitive elite into alignment with those of the
already affluent. The following established tendencies seem likely, say the
authors, to persist and to aggravate existing social frictions:
The latter effect, which is partially documented by the figure, is a direct
consequence of the other two. Unchecked, say Herrnstein and Murray, "these
trends will lead the US toward something resembling a caste society, with the
underclass mired ever more firmly at the bottom and the cognitive elite ever
more firmly anchored at the top, restructuring the rules of society [italics
added] so that it becomes harder and harder for them to lose. . . . Like other
apocalyptic visions, this one is pessimistic, perhaps too much so. On the other
hand, there is much to be pessimistic about."
The last remark would seem to explain why The Bell Curve was written in the
first place. Herrnstein and Murray knew full well that they would be accused of
racism, bigotry, and intellectual dishonesty, just as Arthur Jensen was some 25
years ago, for saying many of the same things. Yet as they (and apparently the
electorate) interpret current events, the nation is in an alarming decline, due
in large part to inadequate leadership and public policy. The forces of darkness
are advancing on every front, and the authors genuinely believe that the
measures they propose will help stem the tide. Many of the policy reforms
proposed by the authors have to do with education. They think it extraordinarily
unwise, for instance, that "only one tenth of 1 percent of all the federal funds
spent on elementary and secondary education go to programs for the gifted."
After all, they say, "The people who run the United States -- create its jobs,
expand its technologies, cure its sick, teach in its universities, administer
its cultural and political institutions_are drawn mainly from a thin layer of
cognitive ability at the top." Since the 1960s, however, "while a cognitive
elite has become increasingly segregated from the rest of the country, the
quality of the education they receive has been degraded." Would they not run
things better if they were better educated? Would they not become the
philosopher kings Plato sought to train?
The Bell Curve has more to say about the nature and causes of the nation's
current decline, and contains more food for thought, than even a lengthy
synopsis can hope to convey. At a guess, the book's most lasting contribution
will be its documentation of the nation's increasing stratification according to
IQtelligence and/or wealth, and its shrill warning against any alliance of the
cognitive and affluent elites. The individual agendas of these groups transcend
traditional party lines, and together they constitute an even greater menace
than Herrnstein and Murray seem to realize: Each group reinforces the other's
instinctive arrogance by lending its prestige to the never-ending quest of every
elite to "restructure the rules of society" to its own advantage.
References
[1] Charles C. Mann, Can meta-analysis make policy?, Science, 266
(November 11, 1994), 960-962.
[2] William Overton, Creationism in schools: the decision in McLean versus the
Arkansas Board of Education, Science, 215 (February 19, 1982), 934-943.
James Case is an independent consultant who lives in Baltimore, Maryland.
Reprinted from SIAM News, Volume 28-01, January 1995
© 1995 by Society for Industrial and Applied Mathematics
All rights reserved.