2020-04-02_Science_Illustrated

quotient is calculated. The scoring system is designed in

such a way that a sufficiently large group of test subjects

will yield results with a normal distribution, a bell-

shaped curve. So most people – about 95% – will have an

IQ of 70-130. Some 70% are in the 85-115 span, meaning

that their intelligence is average. Only 2% score lower

than 70, and a similar 2% score higher than 130. (These

high performers can apply for membership of the

Mensa high IQ society.)

Generally, there is no difference between men’s and

women’s intelligence; both score an average of

100 in intelligence tests. But if we delve into indi-

vidual sections of the tests, we do find a differ-

ence. Women score higher on average than men

in the parts that have to do with language capa-

bilities. Men score higher on questions that have

to do with spatial understanding. There is also a

slight difference in spread between the sexes:

there are more men both at the top and the

bottom, with very low or very high intelligence.

The cause of this has still not been identified.

When intelligence researchers discovered

that we all have an underlying g factor that

determines our score in IQ tests, another ques-

tion was obvious – does it change? Is this a snap-

shot of our mental capabilities, or is our g factor

locked in for life? And that was exactly what Ian

Deary wanted to find out when he began delving

into the old data from the intelligence tests of

those Scottish schoolchildren. And to answer it,

he needed to hunt those schoolchildren down.

The 77 Club Reunion

It was a most unusual reunion at the Aberdeen

Music Theatre on 1 June 1998, when 101 elderly

men and women came together. They were all

born in 1921, so were then 76 or 77 years old, and

they had each participated in the national intel-

ligence study carried out in 1932. Ian Deary and

his employees had found them via newspaper

advertisements and by contacting medical clin-

ics throughout the country. Now they were seated in the

theatre to take exactly the same intelligence test over

which they had first puzzled 66 years earlier.

The reunion provided Ian Deary with a rare opportu-

nity to study what happens to the intelligence of a group

of people over a very long time. He could compare indi-

viduals’ results at the ages of 11 and 77, and could also

get a general idea of how the test subjects had changed

in relation to one another.

The analyses of the results showed two trends. The

vast majority did better in the second test. Deary had

expected that, simply because the test was originally

made for kids; it would be easier for adults. Much more

interesting was that the people who scored above

average as children did so again, and the ones who

scored poorly first time around continued to do so.

Deary also noted a third general conclusion, that the

entire group taken as a whole had scored above average

when they were children. Had this contributed to them

being still alive and healthy enough to take the test for the

second time? Since Deary’s work, other studies have

Which qualities

infl uence our

intelligence?

A study asked

600+ specialists

the question.

They almost all

believed that

a talent for abstract

thinking was key.

Far fewer

believed that

ambition and

motivation

were important.

LANGUAGE

Language understanding,
vocabulary, general knowledge,
the ability to combine data.

EXAMPLE QUESTIONS
What do these have in common:
a painting and a symphony?
(Both are works of art.)
an apple and a pear?
(Both are fruit.)

WORKING

MEMORY

Includes
calculation and the
ability to repeat and
sort out series of
numbers and letters.

EXAMPLE QUESTION
The examiner says the
following: W-4-G-8-L-3.
Now repeat the symbols with
numbers first in numerical
order and then letters in
alphabetical order.
(The answer is 3-4-8-G-L-W.)

PROCESSING

SPEED

Includes the ability

to quickly decode

symbols and organize

them according to simple rules.

EXAMPLE QUESTION

Fill in the blanks below

according to the above rules.

LOGICAL THINKING

Includes spatial understanding

and the ability to draw conclu-

sions based on new material.

EXAMPLE QUESTION

Which figure is next in line?

(B is correct.)

?

A BC

1 2 3 4 5 6 7 8 9

316856137

g

IQ 70

2 % 2 %

14 %

34 % 34 %

14 %

85 100 115 130

68 % of us are in

this group of nor-

mally gifted people.

Abstract thinking: 99%

Problem solving: 98%

Knowledge acquirement: 96%

Ambition/motivation: 19%

Creativity: 60%

General knowledge: 62%

Mental speed: 72%

Memory: 81%

Our intellectual capacity is often divided into four

areas, which each involve a number of different

talents. Combined, the groups reflect our general

intelligence, also known as the g factor. A high g

factor is an indication of a generally gifted person.

The invisible g factor

determines our capacity

SHU

TTE

RST

OCK

IQs have a bell-curve distribution

Based on an intelligence test, scientists can

calculate a person's intelligence quotient, IQ.

The average IQ is 100. When a great number of

people are tested, their IQs will be distributed along

a bell-shaped curve.

› – ◊ = ‹ + @ † ∞

scienceillustrated.com.au | 71