F
or Scottish schoolchildren aged 10-11 on the
1st of June 1932, it was a special day. Instead
of following their usual timetable, the first
lesson involved a different and special chal-
lenge: an IQ test. For 45 minutes the students
worked on the test, which included questions about
words, sentences, numbers and figures. The test, which
had been designed by a psychologist, Sir Godfrey Thom-
son from the University of Edinburgh, aimed to improve
the teaching material of schools and find out how many
students had mental handicaps, so that their education
could be handled in a better way.
The study included 87,498 children, and was the first
of its kind. Up until the 1960s, the extensive data that
resulted was referenced in psychological text books.
Since then it has been largely forgotten, the results
collecting dust in the university’s attics and basements
throughout Edinburgh – until another local psychologist,
Ian Deary, brought them to light again in 1996. Deary
knew exactly what he wanted to use them for. They
were a perfect starting point for a study of what happens
to our intelligence over a life-
time. Does it change, or do we
become more or less intelligent
as we grow older? Perhaps the
old data could even be used to
find out why some people are
more intelligent than others.
Like all other intelligence
researchers, Ian Deary is chal-
lenged by the fact that intelli-
gence itself is a subject which is
very hard to pin down. It is diffi-
cult even to form a definition on
which scientists will agree. It
has often been said that if you
ask 25 intelligence researchers
to define intelligence, you will
get 25 different answers. So
unsurprisingly there is also
similar disagreement when it
comes to the interpretation of
results produced by intelligence
studies. Not only that, the last century has shown that
some facets of intelligence research can be socially and
politically controversial.Defining intelligence
In 1994, American psychologist Linda Goddfredson set
out to do the impossible, trying to make the world’s
leading intelligence researchers agree. Gottfredson felt
that there was a need for researchers to collaborate in
telling the public what scientists had discovered
concerning human intelligence. She drew up 25 short
conclusions and asked 131 university professors to sign.
Less than half of them agreed – 52 in total – but on 13
December 1994, the Wall Street Journal published the
conclusions. The first of these was simply an attempt to
define the very concept of intelligence.
“Intelligence is a very general mental capability that,
among other things, involves the ability to reason, plan,
solve problems, think abstractly, comprehend complexideas, learn quickly, and learn from experience. It is not
merely book learning, a narrow academic skill, or
test-taking smarts. Rather, it reflects a broader and
deeper capability for comprehending our surroundings- ‘catching on’, ‘making sense’ of things, or ‘figuring out’
what to do.”
The length of this definition reveals how difficult it
is to explain the concept of intelligence. Gottfredson’s
difficulties are also highlighted by the fact that she felt
the need to talk about what intelligence is not.
Her definition is an attempt to pin down a concept
within intelligence research known as the ‘g’ factor
(g signifying ‘general intelligence’). English psychologist
Charles Spearman was early on the track of the g factor
in 1904, when he was working with the results of
more schoolchildren who had been tested for different
mental capabilities. To his surprise, and that of other
psychologists, he discovered a general pattern across
the test results. If a student scored highly in one disci-
pline, there was an overall likelihood that the same
student would also score high in the other disciplines.
And similarly if a student scored poorly in one field, it
was highly likely that he or she also scored below aver-
age in the other ones.
Think of a number
The discovery of the g factor made it clear that there is
not much in the way of swings and roundabouts when
it comes to intelligence. The g factor is in direct conflict
with the common view that if there is something that
you are bad at, there’s probably something else that you
are good at. Rather it says there is an underlying general
intelligence that influences our intellectual capacities in
all fields positively or negatively. But of course we all
have our different strengths and weaknesses. The prob-
lem with the g factor is how to measure it directly, disre-
garding such specific capabilities in different fields. We
can only get an indirect impression of the g factor by
designing intelligence tests in such a way that the over-
all result will reflect it as effectively as possible.
The first intelligence tests were developed by French
psychologists Alfred Binet and Théordore Simon in 1905,
then developed further, until in 1916 they were designed
with the possibility of calculating an intelligence
quotient, or ‘IQ’, based on the results. The basic concepts
have held the test of time; modern IQ tests are still
inspired by one of Spearman’s students, American
psychologist David Wechsler, who refined the tests
further in the middle of the last century.
Psychologists’ IQ tests can be designed in different
ways, but they typically include questions that test
language skills, the understanding of symbols, calcula-
tion skills, number processing, logical thinking, and
spatial capabilities. Test subjects can take all the time
they want to complete some tests, but others take place
against the clock, with simple questions in which test
subjects are asked to match a series of numbers and
symbols based on a list on which each symbol is related
to a number. The test subjects must solve as many prob-
lems as possible within a given time-frame.
An IQ test comes with a scoring system, and based
on the test subject’s results, his or her intelligenceWhether you live
to collect your
old-age pension
depends in part on
your IQ at age 11.INTELLIGENCE RESEARCHER IAN DEARY
on the relationship between IQ and life expectancy.THE(^) UN
IVE
RSI
TY (^) O
F (^) ED
INB
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GH
70 | SCIENCE ILLUSTRATED
HUMANS INTELLIGENCE