by Ian J. Deary
Intelligence: A Very Short Introduction
‘I can, and shall, recommend this engaging book to anyone, student or layperson … a reasoned and reasonable view of this interesting and important topic.’
Professor N. J. Mackintosh, Cambridge University
‘This book, written by one of the world’s leading researchers on intelligence, provides an ideal introduction to a controversial topic. Deary … tells us in an entertaining and clear way what was done, what was found, and what it does and does not mean. … If you want to know how we know what we know about intelligence read this book.’
Nat Brody, Wesleyan University
‘Professor Deary’s short introductory book about human intelligence is like no other account available. He addresses the big issues that the experts continue to debate … all in an easy-to-digest, balanced style that meets his aim to put the reader in touch with the scientific research into this challenging field. This book is first class.’
Ted Nettelbeck, Adelaide University
‘succinct and highly readable … an excellent overview of what is and is not known about human intelligence … A gem of a book that will be of interest to a wide audience.’
Tony Vernon, University of Western Ontario
* * *
VERY SHORT INTRODUCTIONS are for anyone wanting a stimulating and accessible way in to a new subject. They are written by experts, and have been published in more than 25 languages worldwide.
The series began in 1995, and now represents a wide variety of topics in history, philosophy, religion, science, and the humanities. Over the next few years it will grow to a library of around 200 volumes – a Very Short Introduction to everything from ancient Egypt and Indian philosophy to conceptual art and cosmology.
* * *
Very Short Introductions available now:
ANCIENT PHILOSOPHY Julia Annas
THE ANGLO-SAXON AGE John Blair
ANIMAL RIGHTS David DeGrazia
ARCHAEOLOGY Paul Bahn
ARCHITECTURE Andrew Ballantyne
ARISTOTLE Jonathan Barnes
ART HISTORY Dana Arnold
ART THEORY Cynthia Freeland
THE HISTORY OF ASTRONOMY Michael Hoskin
ATHEISM Julian Baggini
AUGUSTINE Henry Chadwick
BARTHES Jonathan Culler
THE BIBLE John Riches
BRITISH POLITICS Anthony Wright
BUDDHA Michael Carrithers
BUDDHISM Damien Keown
CAPITALISM James Fulcher
THE CELTS Barry Cunliffe
CHOICE THEORY Michael Allingham
CHRISTIAN ART Beth Williamson
CLASSICS Mary Beard and John Henderson
CLAUSEWITZ Michael Howard
THE COLD WAR Robert McMahon
CONTINENTAL PHILOSOPHY Simon Critchley
COSMOLOGY Peter Coles
CRYPTOGRAPHY Fred Piper and Sean Murphy
DADA AND SURREALISM David Hopkins
DARWIN Jonathan Howard
DEMOCRACY Bernard Crick
DESCARTES Tom Sorell
DRUGS Leslie Iversen
THE EARTH Martin Redfern
EGYPTIAN MYTHOLOGY Geraldine Pinch
EIGHTEENTH-CENTURY BRITAIN Paul Langford
THE ELEMENTS Philip Ball
EMOTION Dylan Evans
EMPIRE Stephen Howe
ENGELS Terrell Carver
ETHICS Simon Blackburn
THE EUROPEAN UNION John Pinder
EVOLUTION Brian and Deborah Charlesworth
FASCISM Kevin Passmore
THE FRENCH REVOLUTION William Doyle
FREUD Anthony Storr
GALILEO Stillman Drake
GANDHI Bhikhu Parekh
GLOBALIZATION Manfred Steger
HEGEL Peter Singer
HEIDEGGER Michael Inwood
HINDUISM Kim Knott
HISTORY John H. Arnold
HOBBES Richard Tuck
HUME A. J. Ayer
IDEOLOGY Michael Freeden
INDIAN PHILOSOPHY Sue Hamilton
INTELLIGENCE Ian J. Deary
ISLAM Malise Ruthven
JUDAISM Norman Solomon
JUNG Anthony Stevens
KANT Roger Scruton
KIERKEGAARD Patrick Gardiner
THE KORAN Michael Cook
LINGUISTICS Peter Matthews
LITERARY THEORY Jonathan Culler
LOCKE John Dunn
LOGIC Graham Priest
MACHIAVELLI Quentin Skinner
MARX Peter Singer
MATHEMATICS Timothy Gowers
MEDIEVAL BRITAIN John Gillingham and Ralph A. Griffiths
MODERN IRELAND Senia Pašeta
MOLECULES Philip Ball
MUSIC Nicholas Cook
NIETZSCHE Michael Tanner
NINETEENTH-CENTURY BRITAIN Christopher Harvie and H. C. G. Matthew
NORTHERN IRELAND Marc Mulholland
PAUL E. P. Sanders
PHILOSOPHY Edward Craig
PHILOSOPHY OF SCIENCE Samir Okasha
PLATO Julia Annas
POLITICS Kenneth Minogue
POLITICAL PHILOSOPHY David Miller
POSTCOLONIALISM Robert Young
POSTMODERNISM Christopher Butler
POSTSTRUCTURALISM Catherine Belsey
PREHISTORY Chris Gosden
PRESOCRATIC PHILOSOPHY Catherine Osborne
PSYCHOLOGY Gillian Butler and Freda McManus
QUANTUM THEORY John Polkinghorne
ROMAN BRITAIN Peter Salway
ROUSSEAU Robert Wokler
RUSSELL A. C. Grayling
RUSSIAN LITERATURE Catriona Kelly
THE RUSSIAN REVOLUTION S. A. Smith
SCHIZOPHRENIA Chris Frith and Eve Johnstone
SCHOPENHAUER Christopher Janaway
SHAKESPEARE Germaine Greer
SOCIAL AND CULTURAL ANTHROPOLOGY John Monaghan and Peter Just
SOCIOLOGY Steve Bruce
SOCRATES C. C. W. Taylor
SPINOZA Roger Scruton
STUART BRITAIN John Morrill
TERRORISM Charles Townshend
THEOLOGY David F. Ford
THE TUDORS John Guy
TWENTIETH-CENTURY BRITAIN Kenneth O. Morgan
WITTGENSTEIN A. C. Grayling
WORLD MUSIC Philip Bohlman
Available soon:
AFRICAN HISTORY John Parker and Richard Rathbone
ANCIENT EGYPT Ian Shaw
THE BRAIN Michael O’Shea
BUDDHIST ETHICS Damien Keown
CHAOS Leonard Smith
CHRISTIANITY Linda Woodhead
CITIZENSHIP Richard Bellamy
CLASSICAL ARCHITECTURE Robert Tavernor
CLONING Arlene Judith Klotzko
CONTEMPORARY ART Julian Stallabrass
THE CRUSADES Christopher Tyerman
DERRIDA Simon Glendinning
DESIGN John Heskett
DINOSAURS David Norman
DREAMING J. Allan Hobson
ECONOMICS Partha Dasgupta
THE END OF THE WORLD Bill McGuire
EXISTENTIALISM Thomas Flynn
THE FIRST WORLD WAR Michael Howard
FREE WILL Thomas Pink
FUNDAMENTALISM Malise Ruthven
HABERMAS Gordon Finlayson
HIEROGLYPHS Penelope Wilson
HIROSHIMA B. R. Tomlinson
HUMAN EVOLUTION Bernard Wood
INTERNATIONAL RELATIONS Paul Wilkinson
JAZZ Brian Morton
MANDELA Tom Lodge
MEDICAL ETHICS Tony Hope
THE MIND Martin Davies
MYTH Robert Segal
&
nbsp; NATIONALISM Steven Grosby
PERCEPTION Richard Gregory
PHILOSOPHY OF RELIGION Jack Copeland and Diane Proudfoot
PHOTOGRAPHY Steve Edwards
THE RAJ Denis Judd
THE RENAISSANCE Jerry Brotton
RENAISSANCE ART Geraldine Johnson
SARTRE Christina Howells
THE SPANISH CIVIL WAR Helen Graham
TRAGEDY Adrian Poole
THE TWENTIETH CENTURY Martin Conway
For more information visit our web site
www.oup.co.uk/vsi
Ian J. Deary
Intelligence
A Very Short Introduction
Great Clarendon Street, Oxford OX2 6DP
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© Ian J. Deary 2001
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ISBN 10: 0-19-289321-1
ISBN 13: 978-0-19-289321-5
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Contents
List of illustrations
Preface and acknowledgements
A word about correlation
1 To see ‘g’ or not to see ‘g’ …
How many types of intelligence are there?
2 Ageing and intelligence: senility or sagacity?
What happens to mental abilities as we grow older?
3 Brainy?
Why are some people cleverer than others?
4 ‘They f—— you up, your mum and dad’ (Larkin)
Are intelligence differences a result of genes or environments or both?
5 The (b)right man for the job
Does intelligence matter?
6 The lands of the rising IQ
Is intelligence increasing generation after generation?
7 Eleven Twelve (not-so-)angry men (and women)
Psychologists actually agree about human intelligence differences
Further reading
Index
List of illustrations
1 WAIS-III structure
2 Matrix reasoning test
Courtesy of John Raven
3 Digit symbol-coding-type test
4 Carroll’s structure of intelligence
5 Moray House Test scattergram 1932–98
6 Scottish Mental Survey 1932 specimen test
7 Scottish Mental Survey 1932 participants resit Moray House Test in 1998
Courtesy of the Aberdeen Press and Journal
8 Design of the Seattle Longitudinal Study
9 Age changes in verbal and non-verbal ability
10 Salthouse’s cognitive ageing theory
11 Measuring brain volume
12 The brain’s electrical response
13 Inspection time
14 Reaction time
15 Identical twins reared together
16 Non-identical twins reared together
17 Identical twins reared apart
18 Non-identical twins reared apart
19 Photograph of identical twins reared apart
Photo: Tom K. Wanstall, Firehouse magazine
20 IQ similarity in identical twins reared apart
21 The OctoTwin study report
© 1997 American Association for the Advancement of Science
22 Adoption
23 OctoTwin study diagram: heritability of intelligence in old age
24 Predicting job performance
25 IQ gains in different nations
26 IQ: knowns and unknowns
© American Psychological Association
Preface and acknowledgements
People value their powers of thinking, and most of us are interested in why some people seem to drive a highly tuned Rolls Royce brain while others potter along with a merely serviceable Ford Fiesta. The fact that the broad powers of human intelligence show differences has been recognized since antiquity. Our language is full of words that signify the possession or lack of an efficient brain. Within the academic discipline of psychology there is a subsection of researchers and teachers called ‘differential psychologists’. They study the differences between people in intelligence and personality. In this short book, I want to describe what they have discovered about how and why people differ in their thinking powers.
There are many books on human intelligence differences and it needed a good reason to add one to the pile. Beyond the tracts written by academics for their peers and students, two sorts of popular book predominate. On the one hand there are many test-your-IQ-type books that offer an introduction to the field of mental measurement. Depending on how you score on their tests, they will flatter or depress. They act as a sort of do-it-yourself fitness diagnosis for your brain. They are a mostly harmless diversion: probably it’s only rather bright people who buy them anyway, and end up rather pleased with the results. On the other hand, there are books which denounce IQ testing as a form of social evil, as a tool used by a social elite to keep the lower orders in their places. Neither of these types of book is satisfactory for understanding the key information about human mental abilities. The former is a quack diagnostic kit and the latter sells a political message that relegates research facts and emphasizes spin.
And it is facts that drive this present book. It is an attempt to cut out the middle man and put you in touch with some actual research data in human intelligence. There is no such thing as a theory of human intelligence differences – not in the way that grown-up sciences like physics or chemistry have theories. We don’t know enough about the workings of the brain to say why some brains seem to be more efficient than others. However, there are some hard facts about human intelligence differences. Just as in other sciences, these hard facts constrain what we can say about the topic: we should not be claiming things that go against or ignore the best evidence in the field. And just as we should expect of a science, we also have to be frank in admitting the faults of each study, especially when the results seem to agree with our own prejudices. The best scientists are their own most severe critics.
The plan of the book is to present a series of diagrams, each of which captures a solid finding about human intelligence differences. Here and there, the diagrams might look quite complicated. The promise is that you will understand them by reading the accompanying text. My efforts have been ai
med toward a clear, non-technical, but also uncompromisingly accurate, account of some of the important areas in human intelligence. The sources from which I drew the information are fully documented here, but no one study is without fault and no single study can settle an issue. My opinion, though, is that it is better to know some influential studies and their main results than merely to amass third-hand accounts which sell a point of view by selective reporting.
I’ve selected 11 sets of research results, 11 datasets, that I think address central questions about human intelligence: not exactly ‘11 datasets that shook the world’, but all are influential in the field. Some of these are remarkable single sets of data that represent huge amounts of effort, luck, and/or ingenuity on the part of the investigator(s). Some of them are collections of studies on a topic that have taken decades to put together and synthesize. There are some descriptions of the work involved in conducting the studies, so that they are not just dry numerical accounts. The datasets address some of the most interesting questions about human intelligence: what forms does it take?; what happens to it as we grow old?; are its origins in our genetic code and the environment’s influences?; does it matter in real life?; why is it rising generation after generation?; and do psychologists themselves agree about intelligence?
For each of the datasets I have chosen one or more illustrations that capture some important aspect of the results. Most of these illustrations originally appeared in the research articles reporting the data. Rather than reproduce these sometimes technical diagrams, they are redrawn in a more accessible form.
Really the 11 datasets are just introductions to a field in which many of us are spending our research lives investigating one or more small patches. In order to assist interested readers in following up some specific topics, there are suggestions at the end of each chapter for how you might develop your interest in the given areas and do some further reading. There is also a section at the end of the book offering general ideas on further resources.
