Mental Chronometry and Individual Differences
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CLOCKING THE MIND i Related books Encyclopedia of Social Measurement, Three-volume set, 1–3 K. KEMPF-LEONARD Measurement, Judgement, and Decision Making BIRNBAUM The Scientific Study of General Intelligence: Tribute to Arthur R. Jensen H. NYBORG (ED.) The Scientific Study of Human Nature: Tribute to Hans J. Eysenck H. NYBORG (ED.) Related Journals — Sample copies available online from http://www.elsevier.com Personality and Individual Differences Intelligence Journal of Personality Research Journal of Mathematical Psychology Organizational Behavior and Human Decision Process ii CLOCKING THE MIND MENTAL CHRONOMETRY AND INDIVIDUAL DIFFERENCES BY ARTHUR R. JENSEN Amsterdam ● Boston ● Heidelberg ● London ● New York ● Oxford Paris ● San Diego ● San Francisco ● Singapore ● Sydney ● Tokyo iii Elsevier The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK Radarweg 29, PO Box 211, 1000 AE Amsterdam, The Netherlands First edition 2006 Copyright © 2006 Elsevier Ltd. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; email: [email protected]. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN-13: 978-0-08-044939-5 ISBN-10: 0-08-044939-5 For information on all Elsevier publications visit our website at books.elsevier.com Printed and bound in The Netherlands 060708091010987654321 iv To the memory of Frans C. Donders (1818–1898) The Originator of Mental Chronometry v This page intentionally left blank vi Contents Preface ix Acknowledgments xiii 1. A Brief Chronology of Mental Chronometry 1 2. Chronometric Terminology and Paradigms 11 3. Reaction Time as a Function of Experimental Conditions 43 4. The Measurement of Chronometric Variables 55 5. Chronometry of Mental Development 75 6. Chronometry of Cognitive Aging 95 7. The Heritability of Chronometric Variables 127 8. The Factor Structure of Reaction Time in Elementary Cognitive Tasks 137 9. Correlated Chronometric and Psychometric Variables 155 10. Sensory Intake Speed and Inspection Time 187 11. Theory of the Correlation Between Response Time and Intelligence 199 12. The Relation of RT to Other Psychological Variables 215 13. Clinical and Medical Uses of Chronometry 231 14. Standardizing Chronometry 237 vii viii Contents References 247 Jensen References on Chronometry Not Cited in the Text 261 Author Index 263 Subject Index 269 Preface Mental chronometry is the measurement of cognitive speed. It is the actual time taken to process information of different types and degrees of complexity. The basic measurement is an individual’s response time (RT) to a visual or auditory stimulus that calls for a par- ticular response, choice, or decision. The elementary cognitive tasks used in chronometric research are typically very simple, seldom eliciting RTs greater than one or two seconds in the normal population. Just another methodology for psychology? Mental chronometry undeniably has its own methodology. But it is also much more than just another method of what psychologists know as data analysis. Chronometric methods generate a generically different order of measurement than do any of our psychometric tests. Scientific research and analysis are rightfully more than just data, numbers, mathematics, and statistical hypothesis testing, yet contemporary psychology has more than its share of these appurtenances. More than in most other scientific fields, research psychologists, espe- cially differential psychologists, confront a plethora of journals, textbooks, and specialized courses on innumerable quantitative methods and statistical techniques. These all are offered wholly without specific reference to any of the field’s substantive topics, empirical or theo- retical. In the physical and biological sciences typically the methodological aspects and ana- lytic methods are more intrinsically inseparable from the particular phenomena and the theoretical questions that are more or less unique to the special field of study. Why? A likely explanation of this condition can be stated as a general rule: The lower the grade of measurement used to represent the variables of interest, the more their quantita- tive description and analysis must depend upon complex statistical methods. Even then, the kinds of questions that can be answered by applying the most sophisticated statistical methods to lower grades of measurement are importantly limited. Quantitative research in virtually all of the behavioral and social sciences is based almost entirely on the lowest grade of measurement that can still qualify as being quantitative, that is, ordinal or rank- order scales. Chronometry, on the other hand, allows us to jump up to the highest grade of measurement, that is, a true ratio scale. Its crucial advantages, though mainly scientific, also have aesthetic appeal. The discovery of the form of a functional relationship between variables when measured on a ratio scale represents a scientific truth, a physical reality, not just an artifice of merely ordinal measurement or of any possible mathematical transfor- mation to which an ordinal scale may be subjected. Measurements can always be trans- formed from a ratio scale to an ordinal scale, but never the reverse. One derives something ix x Preface akin to aesthetic pleasure in discovering a fact of nature that is afforded only by true meas- urement. Many relationships between different behavioral phenomena that we may accept as true by casual observation or from only ordinal measurement could, in principle, be illu- sory. Chronometric measurement, however, can in principle confirm or disconfirm beyond question their validity as scientific fact, of course, always within certain explicit boundary conditions. Hence, a graphic presentation of chronometric data represents a true relation- ship, a fact of nature. An example of this is demonstrated by what I have called the first two laws of individ- ual differences. They just happen to have important implications for interpreting the effects of education: (1) individual differences in learning and performance increase as task com- plexity increases; (2) individual differences in performance increase with continuing prac- tice and experience, unless the task itself imposes an artificially low ceiling on proficiency. These lawful phenomena are amply demonstrated by a variety of reaction time paradigms. But they could not be demonstrated definitively with any form of measurement lower than a ratio scale. Because it has a true or natural zero point, it is the only type of scale that per- mits fully meaningful comparison of the relative differences between means and standard deviations, or the variance ratio, σ /µ. It is also of significant importance that chronometric variables are related to psycho- metric measures of cognitive ability and especially to psychometric g. There is also a chronometric g factor, derived from a battery of various chronometric tasks, which is closely related to psychometric g. But chronometric data also reflect a more profoundly biological basis than do psychometric test scores. For example, it is a fact that IQ, and psy- chometric g even more, measured relatively early in the life span are positively correlated with individual differences in longevity. It was recently shown in a convincingly large sam- ple that persons’ age of death is even more closely related to quite elementary chronomet- ric measures, such as simple and four-choice RT, than it is to IQ (Deary & Der, 2005b). In fact, the RT measures are the primary basis of the psychometric correlations, as there was no significant relationship between IQ and longevity when the effect of RT was statisti- cally removed. Also, statistically controlling several social background variables showed no significant effect on this result. Individual differences in cognitive abilities must ultimately be explained in terms of the physical structures and functions of the brain. Much of the research and theorizing in the field of cognitive psychology has helped in describing more precisely the mental charac- teristics of variation in psychometric g and other psychometric factors than has been pos- sible within the field of psychometrics. But the theoretical formulations of cognitive psychology are strictly mentalistic, and as such they afford no hooks or handles or lever- age of any kind for discovering the physical brain processes that accomplish cognitive behavior or cause individual differences therein.