On Nov 10, 4:02 pm, Sarah Vaughan wrote:
Does anyone know of any good articles/studies on how well IQ scores in
childhood correlate with success in adulthood, given all the inherent
inaccuracies of the tests? I realise this is a pretty broad topic, but
I know there are some well-informed people here, and the subject has
come up for discussion on someone's blog so I'm interested in finding
out more.

Linda Gottfredson has studied how IQ predicts health and longevity and
academic and career success, and her papers are available online at
http://www.udel.edu/educ/gottfredson...nts/index.html .

Here is an article discussing how IQ differences between siblings
predict future income, illegitimate births, and divorce. Looking at
siblings is a simple way to control for socioeconomic status of the
parents.

http://www.eugenics.net/papers/murray.html
IQ Will Put You In Your Place
By Charles Murray

From the Sunday Times, UK, May 25 1997.

A longer version of this article appears in the summer issue of The
Public Interest.

Imagine several hundred families which face few of the usual problems
that plague modern society. Unemployment is zero. Illegitimacy is
zero. Divorce is rare and occurs only after the children's most
formative years. Poverty is absent - indeed, none of the families is
anywhere near the poverty level. Many are affluent and all have enough
income to live in decent neighbourhoods with good schools and a low
crime rate. If you have the good fortune to come from such a
background, you will expect a bright future for your children. You
will certainly have provided them with all the advantages society has
to offer. But suppose we follow the children of these families into
adulthood. How will they actually fare?

A few years ago the late Richard Herrnstein and I published a
controversial book about IQ, The Bell Curve, in which we said that
much would depend on IQ. On average, the bright children from such
families will do well in life - and the dull children will do poorly.
Unemployment, poverty and illegitimacy will be almost as great among
the children from even these fortunate families as they are in society
at large - not quite as great, because a positive family background
does have some good effect, but almost, because IQ is such an
important factor.

"Nonsense!" said the critics. "Have the good luck to be born to the
privileged and the doors of life will open to you - including doors
that will let you get a good score in an IQ test. Have the bad luck to
be born to a single mother struggling on the dole and you will be held
down in many ways - including your IQ test score." The Bell Curve's
purported relationships between IQ and success are spurious, they
insisted: nurture trumps nature; environment matters more than
upbringing.

An arcane debate about statistical methods ensued. Then several
American academics began using a powerful, simple way of testing who
was right: instead of comparing individual children from different
households, they compared sibling pairs with different IQs. How would
brothers and sisters who were nurtured by the same parents, grew up in
the same household and lived in the same neighbourhood, but had
markedly different IQs, get on in life?

The research bears out what parents of children with unequal abilities
already know - that try as they might to make Johnny as bright as
Sarah, it is difficult, and even impossible, to close the gap between
them.

A very large database in the United States contains information about
several thousand sibling pairs who have been followed since 1979. To
make the analysis as unambiguous as possible, I have limited my sample
to brothers and sisters whose parents are in the top 75 per cent of
American earners, with a family income in 1978 averaging £40,000 (in
today's money).

Families living in poverty, or even close to it, have been excluded.
The parents in my sample also stayed together for at least the first
seven years of the younger sibling's life.

Each pair consists of one sibling with an IQ in the normal range of
90-110 ,a range that includes 50% of the population. I will call this
group the normals. The second sibling in each pair had an IQ either
higher than 110, putting him in the top quartile of intelligence (the
bright) or lower than 90, putting him in the bottom quartile (the
dull). These constraints produced a sample of 710 pairs.

How much difference did IQ make? Earned income is a good place to
begin. In 1993, when we took our most recent look at them, members of
the sample were aged 28-36. That year, the bright siblings earned
almost double the average of the dull: £22,400 compared to £11,800.
The normals were in the middle, averaging £16,800.

These differences are sizeable in themselves. They translate into even
more drastic differences at the extremes. Suppose we take a salary of
£50,000 or more as a sign that someone is an economic success. A
bright sibling was six-and-a-half times more likely to have reached
that level than one of the dull. Or we may turn to the other extreme,
poverty: the dull sibling was five times more likely to fall below the
American poverty line than one of the bright. Equality of opportunity
did not result in anything like equality of outcome. Another poverty
statistic should also give egalitarians food for thought: despite
being blessed by an abundance of opportunity, 16.3% of the dull
siblings were below the poverty line in 1993. This was slightly higher
than America's national poverty rate of 15.1%.

Opportunity, clearly, isn't everything. In modern America, and also, I
suspect, in modern Britain, it is better to be born smart and poor
than rich and stupid. Another way of making this point is to look at
education. It is often taken for granted that parents with money can
make sure their children get a college education. The young people in
our selected sample came from families that were overwhelmingly likely
to support college enthusiastically and have the financial means to
help. Yet while 56% of the bright obtained university degrees, this
was achieved by only 21% of the normals and a minuscule 2% of the
dulls. Parents will have been uniformly supportive, but children are
not uniformly able.

The higher prevalence of college degrees partly explains why the
bright siblings made so much more money, but education is only part of
the story. Even when the analysis is restricted to siblings who left
school without going to college, the brights ended up in the more
lucrative occupations that do not require a degree, becoming
technicians, skilled craftsmen, or starting their own small
businesses. The dull siblings were concentrated in menial jobs.

The differences among the siblings go far beyond income. Marriage and
children offer the most vivid example. Similar proportions of siblings
married, whether normal, bright or dull - but the divorce rate was
markedly higher among the dull than among the normal or bright, even
after taking length of marriage into account. Demographers will find
it gloomily interesting that the average age at which women had their
first birth was almost four years younger for the dull siblings than
for the bright ones, while the number of children born to dull women
averaged 1.9, half a child more than for either the normal or the
bright. Most striking of all were the different illegitimacy rates. Of
all the first-born children of the normals, 21% were born out of
wedlock , about a third lower than the figure for the United States as
a whole, presumably reflecting the advantaged backgrounds from which
the sibling sample was drawn. Their bright siblings were much lower
still, with less than 10% of their babies born illegitimate.
Meanwhile, 45% of the first-born of the dull siblings were born
outside of marriage.

The inequalities among siblings that I have described are from 1993
and are going to become much wider in the years ahead. The income
trajectory for low-skill occupations usually peaks in a worker's
twenties or thirties. The income trajectory for managers and
professionals usually peaks in their fifties. The snapshot I have
given you was taken for an age group of 28-36 when many of the brights
are still near the bottom of a steep rise into wealth and almost all
the dulls' incomes are stagnant or even falling. . . .

The inequalities I have presented are the kind you are used to seeing
in articles that compare inner-city children with suburban ones, black
with white, children of single parents with those from intact
families. Yet they refer to the children of a population more
advantaged in jobs, income and marital stability than even the most
starry-eyed social reformer can hope to achieve.

You may be wondering whether the race, age or education of siblings
affects my figures. More extended analyses exist, but the short answer
is that the phenomena I have described survive such questions.
Siblings who differ in IQ also differ widely in important social
outcomes, no matter how anyone tries to explain away the results.
Ambitious parents may be dismayed by this conclusion, but it is none
the less true for all that.

A final thought: I have outlined the inequalities that result from
siblings with different IQs. Add in a few other personal qualities:
industry, persistence, charm, and the differences among people will
inevitably produce a society of high inequalities, no matter how level
the playing field has been made. Indeed, the more level the playing
field, and the less that accidents of birth enter into it, the more
influence personal qualities will have. I make this point as an
antidote to glib thinking on both sides of the Atlantic and from both
sides of the political spectrum. Inequality is too often seen as
something that results from defects in society that can be fixed by a
more robust economy, more active social programmes, or better schools.
It is just not so.

The effects of inequality cannot be significantly reduced, let alone
quelled, unless the government embarks on a compulsory redistribution
of wealth that raises taxes astronomically and strictly controls
personal enterprise. Some will call this social justice. Others will
call it tyranny. I side with the latter, but whichever position one
takes, it is time to stop pretending that, without such massive
compulsion, human beings in a fair and prosperous society will ever be
much more equal than they are now.