INTELLIGENCE: THE BA TTLE FOR THE MIND INTELLI GEN CE: THE BATTLE FOR THEMIND H. J. VERSUS LEON EYSEN CK KAMIN __M_- This book was devised and produeed by Multimedia Publieations Ine First published in Great Britain 1981 simultaneously by Pan Books Cavaye Place, London SWlO 9PG, in paperback and by The Maemillan Press Ltd London and Basingstoke, in hardcover Macmillan edition reprinted 1983 Editor: Susana Raby Produetion : Arnon Orbaeh Design/Layout : Mike Spike Copyright © Multimedia Publieations Ine Williemstad (Curaeao), Personality Investigatlons, Publieations and Services Ltd and Leon Kamin 1981 Softcover reprint ofthe hardcover Ist edition 1981 978-0-333-31279-7 All rights reserved No part of this book may be reproduced or quoted or stored in a retrieval system or transmitted in any form or manner by way ofelectrical, mechanical or photocopy recording without prior written permission from the publishers, apart from brief quotations in critieal artieIes or reviews ISBN 978-1-349-05960-7 ISBN 978-1-349-05958-4 (eBook) DOI 10.1007/978-1-349-05958-4 British Library Cataloguing in Publication Data Eysenck, Hans Kamin, Leon Intelligence: Tbe battle for the mind References pg. 171-172, 182-187. lncludes index. Photo Credits: Rex Features Ltd-85, 125, 141, 143. Applied Psychology Unit (MRC) Cambridge-25. Miki Koren-12, 58, 86bc, 92, 109. Israel Sun Ltd-48, 86a, 135, 151. Multimedia Publications Inc have endeavoured to observe the legal requirements with regard to the rights of the suppliers of graphie and photographie materials. CONTENTS INTRODUCTION 6 BIOGRAPHIES 8 H. J. EYSENCK 1 WHERE DOES THE CONCEPT COME FROM? 11 2 WHAT ARE INTELLIGENCE TESTS? 16 3 WHAT DO INTELLIGENCE TESTS MEASURE? 23 4 INTELLIGENCE AND ACHIEVEMENT 28 5 SEX, AGE AND INTELLIGENCE 37 6 IS INTELLIGENCE INHERITED? 45 7 THE INFLUENCE OF ENVIRONMENT 53 8 SPECIAL FACTORS: REGRESSION AND MATING SYSTEMS 62 9 BIOLOGICAL MEASUREMENT OF IQ 67 10 RACIAL AND CULTURAL FACTORS 74 11 SOCIAL CONSEQUENCES OF IQ MEASUREMENT 84 LEON KAMIN 12 SOME HISTORICAL FACTS ABOUT IQ TESTING 90 13 THE CYRIL BURT AFFAIR 98 14 SEPARATED IDENTICAL TWINS 106 15 STUDIES OF ADOPTED CHILDREN 114 16 MZ AND DZ TWINS 126 17 KINSHIP CORRELATIONS AND THE MODELLING GAME l34 18 SOME ODDS AND ENDS 140 19 FACTS, WISHES AND EYSENCK'S REFERENCES 147 20 IN CONCLUSION 154 21 REJOINDER TO KAMIN 157 H. 1. EYSENCK'S REFERENCES 172 22 REJOINDER TO EYSENCK 172 LEON KAMIN'S REFERENCES 182 GLOSSARY 188 INDEX 190 INTRODUCTION INTELLIGENCE-one of the most important ways by which we judge one another-is a powerful and emotive issue for parents, teachers, employers and even politicians. But what exactIy is inteIIigence? How is it formed? How much is it re1ated to hereditary factors, and how much to social ones? And, most important of aII, can we develop an objective, scientific way of measuring this aspect of ourselves? This very loaded word has been at the centre of controversial, and at times bitter, debate for rriany years. Few subjects in the social sciences or humanities have inflamed passions with such ferocity, and many scientists, politicians and journalists are guilty of mud-slinging. Their claims and counter-claims have created a quagmire. It is still difficult to find a majority of experts anywhere who would agree on an acceptable definition of intelligence, as weil as on its implications for human behaviour. Professor Eysenck seeks to persuade us that genetic factors determine not only our intelligence but many other aspects of behaviour as weil. Professor Kamin argues with equal determination that intelligence is shaped primarily by environmental factors. This book presents a great debate between two well-known advocates holding diametrically opposed views on intelligence. It gives the reader the rare opportunity of weighing up their arguments, which are sharp, uncompromising and controversiaI. Professors Eysenck and Kamin agreed not to see each other's manuscripts while they were being written. After the finished manuscripts had been accepted for publication, each was sent the other's (previously unseen) manuscript and invited to write a rejoinder. It was understood that the original manuscripts could not be altered in the light of the rejoinders. These rejoinders form part of the book and round off a remarkable clash. INTRODUCTION 7 Criticism and debate are the life-blood of science, and in this very active area of such popular concem, it seems only right that both sides should outline their case, and be subject to informed criticism. Perhaps we should set the stage with the words ofthe authors themselves: "The concept of intelligence. and the question of its heritability, both have important psychological and social consequences. On this, as weil as on several substantive points, we are both agreed. There are also, however, a number of points on wh ich we are disagreed; fortunately most if not all of these are subject to scientific enquiry of an empirical nature, and the results of the many hundreds of studies in the field are discussed in this book in an effort to come to some agreement, or, if that should prove impossible, to delineate as clearly as possible the areas of disagreement that remain, and the possible ways in which these disagreements could be resolved." (H. J. EYSENCK) "The publisher of this volume has asked both Professor Eysenck and me to explain briefly how this book came about. Theformat ofa 'debate', once it was proposed, seemed to me entirely appropriate. My purpose has not been to try to change Professor Eysenck's mind; of that I despair. Hut his has been a voice of considerable public influence. I do not want it thought that his opinions represent those of all scientists, or of all psychologists. Nor would I want his opinionated views to be thought ofas scientific facts. I think that he is wrong, and I think that the facts demonstrate this. I hope and believe that in the process ofrational debate I can convince readers that this is so." (LEON KAMIN) 8 BIOG. EYSENCK H. J. Eysenck was born in Berlin, Germany, in 1916. He left Berlin in 1934 in protest against the Hitler movement, and studied language and literature for a while in Dijon, France, and Exeter, England, before taking up psychology at University College, London, under Cyril Burt. After obtaining his Ph.D. there, he joined the Mill Hili Emergency Hospital during the war as research psychologist, and after the war became psychologist to the Maudsley Hospital. Later he founded the Psychological Department and Laboratory at the Institute of Psychiatry, which is associated with the Maudsley Hospital and is part of the University of London. He was appointed Reader and then Professor at the University of London, and still runs the Department, which has grown to number some thirty academic staff. He has published some three dozen books and some six hundred scientific artides. His main academic interests are personality and individual differences, intelli­ gence, behaviour therapy, behavioural genetics, the study of social attitudes and experimental aesthetics. BIOG. KAMIN 9 Leon Kamin was born in Taunton, Massachusetts on 29th December, 1927. He is currently the Dorman T. Warren Professor. of Psychology at Princeton University, where he was chairman of the Department of Psychology from 1968 to 1974. Leon Kamin is a Fellow of the American Psychological Association, and a member of various professional psychology associations. He is a past President of the Eastern Psychological Association and is currently an executive committee member of the Division of Experimental Psychology of the American Psychological Association. He received the Martin Luther King Junior A ward from the N ew York Society of Clinical Psychologists in 1976, and a special award of the National Education Association Committee on Human Relations in 1978. Professor Kamin has reviewed numerous books, has published over fifty scientific artic1es, and has written chapters in many books. He is also the author of The Scienee and Polities o/IQ. I WHERE DOES THE CONCEPT COMEFROM? The man in the street often speaks of "intelligence". So does the professional psychologist. The meanings attached to the term are not always identical, and indeed may at times seem contradictory. Never­ theless, there will be general agreement that whatever "intelligence" may be, it is not a thing, like a table or achair, or a pig, but a concept, a term which carries meaning and can only be understood by virtue of a whole set of facts and theories associated with it. In the heat of the discussion about intelligence, its inheritance and its social implications, this is sometimes lost sight of. But, as we shall see, the fact that intelligence is a concept is of vital importance in trying to und erstand just what it means, what its limitations are, how it can be defined and measured, and whether or not it is inherited. The position taken in this book is that intelligence as a scientific concept is precisely analogous to temperature and other scientific concepts, and that the difficulties its measurement gives rise to are no different from those to which the measurement of temperature and other scientific concepts gives rise. THE ANCIENT GREEK CONTRIBUTION The origins of the concept are lost in antiquity. We know that Plato and Aristotle already drew a distinction between the cognitive aspects of human nature (those concerned with thinking, problem solving, meditating, reasoning, refiecting and so on) and the hormic aspects of human behaviour (those concerned with emotions, feelings, passions and the will). Cicero later coined the term intelligence. We still use the term intelligence to refer to a person's cognitive powers and intellectual abilities. Having created the concept of intelligence, the Greeks went on to make other important contributions.