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V
THE MEASUREMENT OF INTELLIGENCE
AN EXPLANATION OF AND A COMPLETE GUIDE FOR THE USE OF THE STANFORD REVISION AND EXTENSION OF
The Binet-Simon Intelligence Scale
BY
LEWIS M. TERMAN
PROFESSOR OF PSYCHOLOGY LELAND STANFORD JUNIOR UNIVERSITY
HOUGHTON MIFFLIN COMPANY
BOSTON • NEW YORK • CHICAGO • DALLAS ATLANTA • SAN FRANCISCO GTfje &foerstbe jfDcees Cambridge
COPYRIGHT, I9l6, BY LEWIS M. TERMAN
ALL RIGHTS RESERVED, INCLUDING THE RIGHT TO REPRODUCE THIS BOOK OR PARTS THEREOF IN ANY FORM
QCfje ft(ber*<be
CAMBRIDGE . MASSACHUSETTS PRINTED IN THE U.S.A.
(3to tfte .CUemorp
OF
ALFRED BDfflT
PATIENT RESEARCHER, CREATIVE THINKER, UNPRETENTIOUS SCHOLAR INSPIRING AND FRUITFUL DEVOTEE 4 OF
INDUCTIVE AND DYNAMIC PSYCHOLOGY
EDITOR’S INTRODUCTION
The present volume appeals to the editor of this series as one of the most significant books, viewed from the stand¬ point of the future of our educational theory and practice, that has been issued in years. Not only does the volume set forth, in language so simple that the layman can easily under¬ stand, the large importance for public education of a careful measurement of the intelligence of children, but it also describes the tests which are to be given and the entire pro¬ cedure of giving them. In a clear and easy style the author sets forth scientific facts of far-reaching educational impor¬ tance, facts which it has cost him, his students, and many other scientific workers, years of painstaking labor to ac¬ cumulate.
Only very recently, practically only within the past half- dozen years, have scientific workers begun to appreciate fully the importance of intelligence tests as a guide to edu¬ cational procedure, and up to the present we have been able to make but little use of such tests in our schools. The conception in itself has been new, and the testing procedure has been more or less unrefined and technical. The following somewhat popular presentation of the idea and of the meth¬ ods involved, itself based on a scientific monograph which the author is publishing elsewhere, serves for the first time to set forth in simple language the technical details of giving such intelligence tests.
The educational significance of the results to be obtained from careful measurements of the intelligence of children can hardly be overestimated. Questions relating to the choice of studies, vocational guidance, schoolroom proced-
VU1
EDITOR’S INTRODUCTION
ure, the grading of pupils, promotional schemes, the study of the retardation of children in the schools, juvenile delin¬ quency, and the proper handling of subnormals on the one hand and gifted children on the other, — all alike acquire new meaning and significance when viewed in the light of the measurement of intelligence as outlined in this volume. As a guide to the interpretation of the results of other forms of investigation relating to the work, progress, and needs of children, intelligence tests form a very valuable aid. More than all other forms of data combined, such tests give the necessary information from which a pupil’s possibilities of future mental growth can be foretold, and upon which his further education can be most profitably directed.
The publication of this revision and extension of the original Binet-Simon scale for measuring intelligence, with the closer adaptation of it to American conditions and needs, should mark a distinct step in advance in our educational procedure. It means the perfection of another and a very important measuring stick for evaluating educational prac¬ tices, and in particular for diagnosing individual possibilities and needs. Just now the method is new, and its use some¬ what limited, but it is the confident prediction of many students of the subject that, before long, intelligence tests will become as much a matter of necessary routine in school¬ room procedure as a blood-count now is in physical diagno¬ sis. That our schoolroom methods will in turn become much more intelligent, and that all classes of children, but espe¬ cially the gifted and the slow, will profit by such intellectual diagnosis, there can be but little question.
That any parent or teacher, without training, can give these tests, the author in no way contends. However, the observations of Dr. Kohs, cited in Chapter VII, as well as the experience of the author and others who have given courses in intelligence testing to teachers, alike indicate that
EDITOR’S INTRODUCTION
IX
sufficient skill to enable teachers and school principals to give such tests intelligently is not especially difficult to acquire. This being the case it may be hoped that the requi¬ site training to enable them to handle these tests may be included, very soon, as a part of the necessary pedagogical equipment of those who aspire to administrative positions in our public and private schools.
Besides being of special importance to school officers and to students of education in colleges and normal schools, this volume can confidently be recommended to physicians and social workers, and to teachers and parents interested in intelligence measurements, as at once the simplest and the best explanation of the newly-evolved intelligence tests, which has so far appeared in print.
Ellwood P. Cubberley.
PREFACE
The constant and growing use of the Binet-Simon intel¬ ligence scale in public schools, institutions for defectives, reform schools, juvenile courts, and police courts is suffi¬ cient evidence of the intrinsic worth of the method. It is generally recognized, however, that the serviceableness of the scale has hitherto been seriously limited, both by the lack of a sufficiently detailed guide and by a number of recognized imperfections in the scale itself. The Stanford revision and extension has been worked out for the purpose of correcting as many as possible of these imperfections, and it is here presented with a rather minute description of the method as a whole and of the individual tests.
The aim has been to present the explanations and instruc¬ tions so clearly and in such an untechnical form as to make the book of use, not only to the psychologist, but also to the rank and file of teachers, physicians, and social workers. More particularly, it is designed as a text for use in normal schools, colleges, and teachers’ reading-circles.
While the use of the intelligence scale for research pur¬ poses and for accurate diagnosis will of necessity always be restricted to those who have had extensive training in experimental psychology, the author believes that the time has come when its wider use for more general purposes should be encouraged.
However, it cannot be too strongly emphasized that no one, whatever his previous training may have been, can make proper use of the scale unless he is willing to learn the method of procedure and scoring down to the minutest de¬ tail. A general acquaintance with the nature of the indi¬ vidual tests is by no means sufficient.
PREFACE
Perhaps the best way to learn the method will be to begin by studying the book through, in order to gain a general acquaintance with the tests; then, if possible, to observe a few examinations; and finally to take up the procedure for detailed study in connection with practice testing. Twenty or thirty tests, made with constant reference to the pro¬ cedure as described in Part II, should be sufficient to pre¬ pare the teacher or physician to make profitable use of the scale.
The Stanford revision of the scale is the result of a number of investigations, made possible by the cooperation of the author’s graduate students. Grateful acknowledgment is especially due to Professor H. G. Childs, Miss Grace Lyman, Dr. George Ordahl, Dr. Louise Ellison Ordahl, Miss Neva Galbreath, Mr. Wilford Talbert, Mr. J. Harold Williams, and Mr. Herbert E. Knollin. Without their assistance this book could not have been written.
Stanford University.
April, 1916.
CONTENTS
PART I. PROBLEMS AND RESULTS CHAPTER I
The Uses of Intelligence Tests .
Intelligence tests of retarded school children. Intelligence tests of the feeble-minded. Intelligence tests of delinquents. Intelligence tests of superior children. Intelligence tests as a basis for grading. Intelligence tests for vocational fitness. Other uses of intelligence tests.
CHAPTER II
Sources of Error in Judging Intelligence
Are intelligence tests superfluous? The necessity of standards. The intelligence of retarded children usually overestimated. The intelligence of superior children usually underestimated. Other fallacies in the estimation of intelligence. Binet’s questionnaire on teachers’ methods of judging intelligence. Binet’s experiment on how teachers test intelligence.
CHAPTER III
Description of the Binet-Simon Method .
Essential nature of the scale. How the scale was derived. List of tests. How the scale is used. Special characteristics of the Binet-Simon method. The use of age standards. The kind of mental functions brought into play. Binet would test “general in¬ telligence.” Binet’s conception of general intelligence. Other conceptions of intelligence. Guiding principles in choice and ar¬ rangement of tests. Some avowed limitations of the Binet tests.
CHAPTER IV
Nature of the Stanford Revision and Extension . . Sources of data. Method of arriving at a revision. List of tests in the Stanford revision and extension. Summary of changes. Effects of the revision on the mental ages secured.
XIV
CONTENTS
CHAPTER V
Analysis of One Thousand Intelligence Quotients . 65 The distribution of intelligence. The validity of the intelligence quotient. Sex differences. Intelligence of the different social classes. The relation of the I Q to the quality of the child’s school work. The relation between I Q and grade progress. Correlation between I Q and the teachers’ estimates of the children’s intelligence. The validity of the individual tests.
CHAPTER VI
The Significance of Various Intelligence Quotients 78 Frequency of different degrees of intelligence. Classification of intelligence quotients. Feeble-mindedness. Border-line cases. Examples of border-line deficiency. Dull normals. Average intelligence. Superior intelligence. Very superior intelligence. Examples of very superior intelligence. Genius and “near” genius. Is the I Q often misleading?
CHAPTER VH
Reliability of the Binet-Simon Method . . . .105
General value of the method. Dependence of the scale’s relia¬ bility on the training of the examiner. Influence of the subject’s attitude. The influence of coaching. Reliability of repeated tests. Influence of social and educational advantages.
PART II
GUIDE FOR THE USE OF THE STANFORD REVISION AND EXTENSION
CHAPTER VIII
General Instructions . 121
Necessity of securing attention and effort. Quiet and seclusion. Presence of others. Getting into rapport. Keeping the child en¬ couraged. The importance of tact. Personality of the examiner.
The avoidance of fatigue. Duration of the examination. Desir¬ able range of testing. Order of giving the tests. Coaxing to be avoided. Adhering to formula. Scoring. Recording responses. Scattering of successes. Supplementary considerations. Alterna-
CONTENTS
xv
tive tests. Finding mental age. The use of the intelligence quo¬ tient. How to find the I Q of adult subjects. Material for use in testing.
CHAPTER IX Instructions for Year III
1. Pointing to parts of the body . 142
2. Naming familiar objects . * . 143
3. Enumeration of objects in pictures . 145
4. Giving sex . 146
5. Giving the family name . 147
6. Repeating six to seven syllables . 149
Alternative test: Repeating three digits . 150
CHAPTER X Instructions for Year IV
1. Comparison of lines . 151
2. Discrimination of forms . 152
3. Counting four pennies . 154
4. Copying a square . 155
5. Comprehension, first degree . 157
6. Repeating four digits . 159
Alternative test: Repeating twelve to thirteen syllables . . 160
CHAPTER XI Instructions for Year V
1. Comparison of weights . 161
2. Naming colors . 163
3. .Esthetic comparison . 165
4. Giving definitions in terms of use . 167
5. The game of patience . 169
6. Three commissions . 172
Alternative test: Giving age . 173
CHAPTER XII Instructions for Year VI
1. Distinguishing right and left . 175
2. Finding omissions in pictures . 178
3. Counting thirteen pennies . 180
4. Comprehension, second degree . . . ,• . . . .181
CONTENTS
xvi
5. Naming four coins . 184
6. Repeating sixteen to eighteen syllables . 185
Alternative test: Forenoon and afternoon . 187
CHAPTER XIII Instructions for Year VII
1. Giving the number of fingers . 189
2. Description of pictures . 190
3. Repeating five digits . 193
4. Tying a bow-knot . 196
5. Giving differences from memory . 199
6. Copying a diamond . 204
Alternative test 1: Naming the days of the week . . . 205
Alternative test 2: Repeating three digits reversed . . . 207
CHAPTER XIV
Instructions for Year VIII
1. The ball-and-field test . 210
2. Counting backwards from 20 to 1 . 213
3. Comprehension, third degree . 215
4. Giving similarities, two things . 217
5. Giving definitions superior to use . 221
6. Vocabulary (20 definitions, 3600 words) . 224
Alternative test 1: Naming six coins . 231
Alternative test 2: Writing from dictation . 231
CHAPTER XV Instructions for Year IX
1. Giving the date . 234
2. Arranging five weights . 236
3. Making change . 240
4. Repeating four digits reversed . 242
5. Using three words in a sentence . 242
6. Finding rhymes . 248
Alternative test 1: Naming the months . 251
Alternative test 2: Counting the value of stamps . . . 252
CHAPTER XVI Instructions for Year X
1. Vocabulary (30 definitions, 5400 words) . 255
2. Detecting absurdities .... . 255
CONTENTS xvii
S. Drawing designs from memory . 260
4. Reading for eight memories . 262
5. Comprehension, fourth degree . 268
6. Naming sixty words . 272
Alternative test 1 : Repeating six digits . 277
Alternative test 2: Repeating twenty to twenty-two syllables 277 Alternative test 3: Healy’s Construction Puzzle A . . . 278
CHAPTER XVH
Instructions for Year XII
1. Vocabulary (40 definitions, 7200 words) . 281
2. Defining abstract words . 281
3. The ball-and-field test (superior plan) . 286
4. Dissected sentences . 286
5. Interpretation of fables (score 4) . 290
6. Repeating five digits reversed . 301
7. Interpretation of pictures . 302
8. Giving similarities, three things . 306
CHAPTER XVin
Instructions for Year XIV
1. Vocabulary (50 definitions, 9000 words) . 310
2. Induction test: finding a rule . 310
3. Giving differences between a president and a king . . .313
4. Problem questions . 315
5. Arithmetical reasoning . 319
6. Reversing hands of a clock . 321
Alternative test: Repeating seven digits . ^ . 322
CHAPTER XIX
Instructions for “Average Adult”
1. Vocabulary (65 definitions, 11,700 words) . 324
2. Interpretation of fables (score 8) ....... 324
3. Differences between abstract terms . . . . . . 324
4. Problem of the enclosed boxes . 327
5. Repeating six digits reversed . 329
6. Using a code . 330
Alternative test 1 : Repeating twenty-eight syllables . . 332 Alternative test 2: Comprehension of physical relations . . 333
xvm
CONTENTS
CHAPTER XX
Instructions for “Superior Adult”
1. Vocabulary (75 definitions, 13,500 words) . S38
2. Binet’s paper-cutting test . 338
3. Repeating eight digits . 340
4. Repeating thought of passage . 340
5. Repeating seven digits reversed . 345
6. Ingenuity test . 345
SELECTED REFERENCES . 349
INDEX . 359
FIGURES AND DIAGRAMS
1. Distribution of Mental Ages of 62 Normal Adults .
2. Distribution of I Q’s of 905 Unselected Children, 5-14 Years of Age
3. Median I Q of 457 Boys and 448 Girls, for the Ages 5-14 Years .
4. Diamond drawn by R. W.; Age 13-10; Mental Age 7-6 .
5. Writing from Dictation. R. M., Age 15; Mental Age 9 .
6. Ball and Field Test. I. M., Age 14-2; Mental Age 9
7. Diamond drawn by A. W .
8. Drawing Designs from Memory. H. S., Age 11; Mental Age 8-3
9. Ball and Field Test. S. F., Age 17; Mental Age 11-6
10. Writing from Dictation. C. P., Age 10-2; Mental Age 7-11 .
11. Ball and Field Test. M. P., Age 14; Mental Age 10-8 .
12. Ball and Field Test. R. G., Age 13-5; Mental Age 10-6
13. Ball and Field Test. E. B., Age 7-9; I Q 130 .
14. Ball and Field Test. F. McA., Age 10-3; Mental Age 14-6 .
15. Drawing Designs from Memory. E. M., Age 6-11; Mental Age 10,
I Q 145 .
16. Ball and Field Test. B. F., Age 7 -8; Mental Age 12-4; I Q 160
17. Healy and Fernald Construction Puzzle .
55
66
69
82
83
84
85
86
88
90
91
93
98
100
101
102
279
THE MEASUREMENT OF INTELLIGENCE
PART I
PROBLEMS AND RESULTS
THE MEASUREMENT OF INTELLIGENCE
CHAPTER I
THE USES OF INTELLIGENCE TESTS
Intelligence tests of retarded school children. Numerous studies of the age-grade progress of school children have afforded convincing evidence of the magnitude and serious¬ ness of the retardation problem. Statistics collected in hundreds of cities in the United States show that between a third and a half of the school children fail to progress through the grades at the expected rate; that from 10 to 15 per cent are retarded two years or more; and that from 5 to 8 per cent are retarded at least three years. More than 10 per cent of the $400,000,000 annually expended in the United States for school instruction is devoted to re-teach¬ ing children what they have already been taught but have failed to learn.
The first efforts at reform which resulted from these findings were based on the supposition that the evils which had been discovered could be remedied by the individualiz¬ ing of instruction, by improved methods of promotion, by increased attention to children’s health, and by other re¬ forms in school administration. Although reforms along these lines have been productive of much good, they have nevertheless been in a measure disappointing. The trouble was, they were too often based upon the assump¬ tion that under the right conditions all children would be
4
THE MEASUREMENT OF INTELLIGENCE
equally, or almost equally, capable of making satisfactory school progress. Psychological studies of school children by means of standardized intelligence tests have shown that this supposition is not in accord with the facts. It has been found that children do not fall into two well-defined groups, the “ feeble-minded ” and the “ normal.” Instead, there are many grades of intelligence, ranging from idiocy on the one hand to genius on the other. Among those classed as normal, vast individual differences have been found to exist in original mental endowment, differences which affect profoundly the capacity to profit from school in¬ struction.
We are beginning to realize that the school must take into account, more seriously than it has yet done, the existence and significance of these differences in endowment. In¬ stead of wasting energy in the vain attempt to hold men¬ tally slow and defective children up to a level of progress which is normal to the average child, it will be wiser to take account of the inequalities of children in original endowment and to differentiate the course of study in such a way that each child will be allowed to progress at the rate which is normal to him, whether that rate be rapid or slow.
While we cannot hold all children to the same standard of school progress, we can at least prevent the kind of re¬ tardation which involves failure and the repetition of a school grade. It is well enough recognized that children do not enter with very much zest upon school work in which they have once failed. Failure crushes self-confidence and destroys the spirit of work. It is a sad fact that a large proportion of children in the schools are acquiring the habit of failure. The remedy, of course, is to measure out the work for each child in proportion to his mental ability.
Before an engineer constructs a railroad bridge or trestle.
USES OF INTELLIGENCE TESTS
5
he studies the materials to be used, and learns by means of tests exactly the amount of strain per unit of size his ma¬ terials will be able to withstand. He does not work empiri¬ cally, and count upon patching up the mistakes which may later appear under the stress of actual use. The educational engineer should emulate this example. Tests and fore¬ thought must take the place of failure and patchwork. Our efforts have been too long directed by “ trial and error.” It is time to leave off guessing and to acquire a scientific knowledge of the material with which we have to deal. When instruction must be repeated, it means that the school, as well as the pupil, has failed.
Every child who fails in his school work or is in danger of failing should be given a mental examination. The examina¬ tion takes less than one hour, and the result will con¬ tribute more to a real understanding of the case than any¬ thing else that could be done. It is necessary to determine whether a given child is unsuccessful in school because of poor native ability, or because of poor instruction, lack of interest, or some other removable cause.
It is not sufficient to establish any number of special classes, if they are to be made the dumping-ground for all kinds of troublesome cases — the feeble-minded, the physi¬ cally defective, the merely backward, the truants, the in- corrigibles, etc. Without scientific diagnosis and classi¬ fication of these children the educational work of the special class must blunder along in the dark. In such diagnosis and classification our main reliance must always be in mental tests, properly used and properly interpreted.
Intelligence tests of the feeble-minded. Thus far intelli¬ gence tests have found their chief application in the identi¬ fication and grading of the feeble-minded. Their value for this purpose is twofold. In the first place, it is necessary to ascertain the degree of defect before it is possible to decide
6
THE MEASUREMENT OF INTELLIGENCE
intelligently upon either the content or the method of in¬ struction suited to the training of the backward child. In the second place, intelligence tests are rapidly extending our conception of “ feeble-mindedness ” to include milder degrees of defect than have generally been associated with this term. The earlier methods of diagnosis caused a major¬ ity of the higher grade defectives to be overlooked. Pre¬ vious to the development of psychological methods the low- grade moron was about as high a type of defective as most physicians or even psychologists were able to identify as feeble-minded.
Wherever intelligence tests have been made in any con¬ siderable number in the schools, they have shown that not far from 2 per cent of the children enrolled have a grade of intelligence which, however long they live, will never develop beyond the level which is normal to the average child of 11 or 12 years. The large majority of these belong to the moron grade; that is, their mental development will stop somewhere between the 7-year and 12-year level of intelligence, more often between 9 and 12.
The more we learn about such children, the clearer it be¬ comes that they must be looked upon as real defectives. They may be able to drag along to the fourth, fifth, or sixth grades, but even by the age of 16 or 18 years they are never able to cope successfully with the more abstract and diffi¬ cult parts of the common-school course of study. They may master a certain amount of rote learning, such as that involved in reading and in the manipulation of number com¬ binations, but they cannot be taught to meet new condi¬ tions effectively or to think, reason, and judge as normal persons do.
It is safe to predict that in the near future intelligence tests will bring tens of thousands of these high-grade de¬ fectives under the surveillanee and protection of society.
A
USES OF INTELLIGENCE TESTS
7
This will ultimately result in curtailing the reproduction of feeble-mindedness and in the elimination of an enor¬ mous amount of crime, pauperism, and industrial inef¬ ficiency. It is hardly necessary to emphasize that the high- grade cases, of the type now so frequently overlooked, are precisely the ones whose guardianship it is most important for the State to assume.
Intelligence tests of delinquents. One of the most im¬ portant facts brought to light by the use of intelligence tests is the frequent association of delinquency and mental deficiency. Although it has long been recognized that the proportion of feeble-mindedness among offenders is rather large, the real amount has, until recently, been underesti¬ mated even by the most competent students of criminology.
The criminologists have been accustomed to give more at¬ tention to the physical than to the mental correlates of crime. Thus, Lombroso and his followers subjected thousands of criminals to observation and measurement with regard to such physical traits as size and shape of the skull, bilateral asymmetries, anomalies of the ear, eye, nose, palate, teeth, hands, fingers, hair, dermal sensitivity, etc. The search was for physical “stigmata” characteristic of the “criminal type.”
Although such studies performed an important service in creating a scientific interest in criminology, the theories of Lombroso have been wholly discredited by the results of intelligence tests. Such tests have demonstrated, beyond any possibility of doubt, that the most important trait of at least 25 per cent of our criminals is mental weakness. The physical abnormalities which have been found so common among prisoners are not the stigmata of criminal¬ ity, but the physical accompaniments of feeble-minded¬ ness. They have no diagnostic significance except in so far as they are indications of mental deficiency. Without
8
THE MEASUREMENT OF INTELLIGENCE
exception, every study which has been made of the in¬ telligence level of delinquents has furnished convincing testimony as to the close relation existing between mental weakness and moral abnormality. Some of these findings are as follows : —
Miss Renz tested 100 girls of the Ohio State Reformatory and reported 36 per cent as certainly feeble-minded. In every one of these cases the commitment papers had given the pronouncement “intellect sound.”
Under the direction of Dr. Goddard the Binet tests were given to 100 juvenile court cases, chosen at random, in Newark, New Jersey. Nearly half were classified as feeble-minded. One boy 17 years old had 9-year intelligence; another of 15^ had 8-year intelligence.
Of 56 delinquent girls 14 to 20 years of age tested by Hill and Goddard, almost half belonged either to the 9- or the 10-year level of intelligence.
Dr. G. G. Fernald’s tests of 100 prisoners at the Massachusetts State Reformatory showed that at least 25 per cent were feeble¬ minded.
Of 1186 girls tested by Miss Dewson at the State Industrial School for Girls at Lancaster, Massachusetts, 28 per cent were found to have subnormal intelligence.
Dr. Katherine Bement Davis’s report on 1000 cases entered in the Bedford Home for Women, New York, stated that there was no doubt but that at least 157 were feeble-minded. Recently there has been established at this institution one of the most important research laboratories of the kind in the United States, with a trained psychologist. Dr. Mabel Femald, in charge.
Of 564 prostitutes investigated by Dr. Anna Dwyer in connec¬ tion with the Municipal Court of Chicago, only 3 per cent had gone beyond the fifth grade in school. Mental tests were not made, but from the data given it is reasonably certain that half or more were feeble-minded.
Tests, by Dr. George Ordahl and Dr. Louise Ellison Ordahl, of cases in the Geneva School for Girls, Geneva, Illinois, showed that, on a conservative basis of classification, at least 18 per cent were feeble-minded. At the Joliet Prison, Illinois, the same authors found 50 per cent of the female prisoners feeble-minded.
USES OF INTELLIGENCE TESTS
9
and 26 per cent of the male prisoners. At the St. Charles School for Boys 26 per cent were feeble-minded.
Tests, by Dr. J. Harold Williams, of 150 delinquents in the Whittier State School for Boys, Whittier, California, gave 28 per cent feeble-minded and 25 per cent at or near the border-line. About 300 other juvenile delinquents tested by Mr. Williams gave approximately the same figures. As a result of these findings a research laboratory has been established at the Whittier School, with Dr. Williams in charge. In the girls’ division of the Whittier School, Dr. Grace Fernald collected a large amount of psychologi¬ cal data on more than 100 delinquent girls. The findings of this investigation agree closely with those of Dr. Williams for the boys.
At the State Reformatory, Jeffersonville, Indiana, Dr. von Klein-Schmid, in an unusually thorough psychological study of 1000 young adult prisoners, finds the proportion of feeble-minded¬ ness not far from 50 per cent.
But it is needless to multiply statistics. Those given are but samples. Tests are at present being made in most of the progressive prisons, reform schools, and juvenile courts throughout the country, and while there are minor discrep¬ ancies in regard to the actual percentage who are feeble¬ minded, there is no investigator who denies the fearful role played by mental deficiency in the production of vice, crime, and delinquency.1
Heredity studies of “ degenerate ” families have con¬ firmed, in a striking way, the testimony secured by intelli¬ gence tests. Among the best known of such families are the “ Kallikaks,” the “ Jukes,” the “ Hill Folk,” the “ Nams,” the “ Zeros,” and the “ Ishmaelites.”
The Kallikak family. Martin Kallikak was a youthful soldier in the Revolutionary War. At a tavern frequented by the militia he met a feeble-minded girl, by whom he became the father of a feeble-minded son. In 1912 there were 480 known direct descend¬ ants of this temporary union. It is known that 36 of these were
1 See References at end of volume.
10 THE MEASUREMENT OF INTELLIGENCE
illegitimates, that 33 were sexually immoral, that 24 were con¬ firmed alcoholics, and that 8 kept houses of ill-fame. The explana¬ tion of so much immorality will be obvious when it is stated that of the 480 descendants, 143 were known to be feeble-minded, and that many of the others were of questionable mentality.
A few years after returning from the war this same Martin Kallikak married a respectable girl of good family. From this union 496 individuals have been traced in direct descent, and in this branch of the family there were no illegitimate children, no immoral women, and only one man who was sexually loose. There were no criminals, no keepers of houses of ill-fame, and only two confirmed alcoholics. Again the explanation is clear when it is stated that this branch of the family did not contain a single feeble-minded individual. It was made up of doctors, lawyers, judges, educators, traders, and landholders.1
The Hill Folk. The Hill Folk are a New England family of which 709 persons have been traced. Of the married women, 24 per cent had given birth to illegitimate offspring, and 10 per cent were prostitutes. Criminal tendencies were clearly shown in 24 members of the family, while alcoholism was still more common. The proportion of feeble-minded was 48 per cent. It was esti¬ mated that the Hill Folk have in the last sixty years cost the State of Massachusetts, in charitable relief, care of feeble-minded, epileptic, and insane, conviction and punishment for crime, pros¬ titution, pauperism, etc., at least $500, 000. 2
The Nam family and the Jukes give equally dark pictures as regards criminality, licentiousness, and alcoholism, and although feeble-mindedness was not as fully investigated in these families as in the Kallikaks and the Hill Folk, the evidence is strong that it was a leading trait. The 784 Nams who were traced included 187 alcoholics, 232 women and 199 men known to be licentious, and 40 who became prisoners. It is estimated that the Nams have already cost the State nearly $1,500,000.3
Of 540 Jukes, practically one fifth were born out of wedlock, 37 were known to be syphilitic, 53 had been in the poorhouse, 76
1 H. H. Goddard: The Kallikak Family. (1914.) 141 pp.
2 Danielson and Davenport: The Hill Folk. Eugenics Record Office,
Memoir No. 1. 1912. 56 pp.
8 Estabrook and Davenport: The Nam Family. Eugenics Record Of¬ fice. Memoir No. 2. (1912). 85 pp.
USES OF INTELLIGENCE TESTS
11
had been sentenced to prison, and of 229 women of marriageable age 128 were prostitutes. The economic damage inflicted upon the State of New York by the Jukes in seventy-five years was esti¬ mated at more than $1,300,000, to say nothing of diseases and other evil influences which they helped to spread.1
But why do the feeble-minded tend so strongly to be¬ come delinquent? The answer may be stated in simple terms. Morality depends upon two things: (a) the ability to foresee and to weigh the possible consequences for self and others of different kinds of behavior; and (6) upon the willingness and capacity to exercise self-restraint. That there are many intelligent criminals is due to the fact that (a) may exist without (b). On the other hand, ( b ) presupposes (a). In other wrords, not all criminals are feeble-minded, but all feeble-minded are at least potential criminals. That every feeble-minded woman is a potential prostitute would hardly be disputed by any one. Moral judgment, like business judgment, social judgment, or any other kind of higher thought process, is a function of in¬ telligence. Morality cannot flower and fruit if intelligence remains infantile.
All of us in early childhood lacked moral responsibility. We were as rank egoists as any criminal. Respect for the feelings, the property rights, or any other kind of rights, of others had to be laboriously acquired under the whip of discipline. But by degrees we learned that only when in¬ stincts are curbed, and conduct is made to conform to principles established formally or accepted tacitly by our neighbors, does this become a livable world for any of us. Without the intelligence to generalize the particular, to foresee distant consequences of present acts, to weigh these foreseen consequences in the nice balance of imagina-
1 R. L. Dugdale: The Jukes. (Fourth edition, 1910.) 120 pp. G. P. Putnam’s Sons.
n THE MEASUREMENT OF INTELLIGENCE
tion, morality cannot be learned. When the adult body, with its adult instincts, is coupled with the undeveloped intelligence and weak inhibitory powers of a 10-year-old child, the only possible outcome, except in those cases where constant guardianship is exercised by relatives or friends, is some form of delinquency.
Considering the tremendous cost of vice and crime, which in all probability amounts to not less than $500,000,000 per year in the United States alone, it is evident that psy¬ chological testing has found here one of its richest applica¬ tions. Before offenders can be subjected to rational treat¬ ment a mental diagnosis is necessary, and while intelligence tests do not constitute a complete psychological diagnosis, they are, nevertheless, its most indispensable part.
Intelligence tests of superior children. The number of children with very superior ability is approximately as great as the number of feeble-minded. The future wel¬ fare of the country hinges, in no small degree, upon the right education of these superior children. Whether civi¬ lization moves on and up depends most on the advances made by creative thinkers and leaders in science, politics, art, morality, and religion. Moderate ability can follow, or imitate, but genius must show the way.
Through the leveling influences of the educational lock- step such children at present are often lost in the masses. It is a rare child who is able to break this lockstep by extra promotions. Taking the country over, the ratio of “ ac¬ celerates ” to “ retardates ” in the school is approximately 1 to 10. Through the handicapping influences of poverty, social neglect, physical defects, or educational maladjust¬ ments, many potential leaders in science, art, govern¬ ment, and industry are denied the opportunity of a normal development. The use we have made of exceptional ability reminds one of the primitive methods of surface mining.
USES OF INTELLIGENCE TESTS
13
It is necessary to explore the nation’s hidden resources of intelligence. The common saying that “ genius will out ” is one of those dangerous half-truths with which too many people rest content.
Psychological tests show that children of superior abil¬ ity are very likely to be misunderstood in school. The writer has tested more than a hundred children who were as much above average intelligence as moron defectives are below. The large majority of these were found located below the school grade warranted by their intellectual level. One third had failed to reap any advantage what¬ ever, in terms of promotion, from their very superior intel¬ ligence. Even genius languishes when kept over-long at tasks that are too easy.
Our data show that teachers sometimes fail entirely to recognize exceptional superiority in a pupil, and that the degree of such superiority is rarely estimated with anything like the accuracy which is possible to the psychologist after a one-hour examination. B. F., for example, was a little over 7^2 years old when tested. He was in the third grade, and was therefore thought by his teacher to be accelerated in school. This boy’s intelligence, however, was found to be above the 12-year level. There is no doubt that his mental ability would have enabled him, with a few months of individual instruction, to carry fifth or even sixth-grade work as easily as third, and without injury to body or mind. Nevertheless, the teacher and both the parents of this child had found nothing remarkable about him. In reality he belongs to a grade of genius not found oftener than once in several thousand cases.
Another illustration is that of a boy of years who tested at the “ average adult ” level. He was doing superior work in the sixth grade, but according to the testimony of the teacher had “ no unusual ability.” It was ascertained
14 THE MEASUREMENT OF INTELLIGENCE
from the parents that this boy, at an age when most chil¬ dren are reading fairy stories, had a passion for standard medical literature and textbooks in physical science. Yet, after more than a year of daily contact with this young genius (who is a relative of Meyerbeer, the composer), the teacher had discovered no symptoms of unusual ability.1
Teachers should be better trained in detecting the signs of superior ability. Every child who consistently gets high marks in his school work with apparent ease should be given a mental examination, and if his intelligence level war¬ rants it he should either be given extra promotions, or placed in a special class for superior children where faster progress can be made. The latter is the better plan, because it obviates the necessity of skipping grades; it permits rapid but continuous progress.
The usual reluctance of teachers to give extra promo¬ tions probably rests upon three factors: (1) mere inertia; (2) a natural unwillingness to part with exceptionally satis¬ factory pupils; and (3) the traditional belief that preco¬ cious children should be held back for fear of dire physical or mental consequences.
In order to throw light on the question whether excep¬ tionally bright children are specially likely to be one-sided, nervous, delicate, morally abnormal, socially unadaptable, or otherwise peculiar, the writer has secured rather ex¬ tensive information regarding 31 children whose mental age was found by intelligence tests to be 25 per cent above the actual age. This degree of intelligence is possessed by about 2 children out of 100, and is nearly as far above average intelligence as high-grade feeble-mindedness is below. The supplementary information, which was fur¬ nished in most cases by the teachers, may be summarized as follows : —
1 See p. 26 ,/f. for further illustrations of this kind.
USES OF INTELLIGENCE TESTS
15
1. Ability special or general. In the case of 20 out of 31 the abil- ity is decidedly general, and with 2 it is mainly general. The talents of 5 are described as more or less special, but only in one case is it remarkably so. Doubtful 4.
2. Health. 15 are said to be perfectly healthy; 13 have one or more physical defects; 4 of the 13 are described as delicate; 4 have adenoids; 4 have eye-defects; 1 lisps; and 1 stutters. These figures are about the same as one finds in any group of ordinary children.
3. Studiousness. “Extremely studious,” 15; “usually studious” or “fairly studious,” 11; “not particularly studious,” 5; “lazy,” 0.
4. Moral traits. Favorable traits only, 19; one or more unfavor¬ able traits, 8; no answer, 4. The eight with unfavor¬ able moral traits are described as follows: 2 are “very self- willed”; 1 “needs close watching”; 1 is “cruel to animals”; 1 is “untruthful”; 1 is “unreliable”; 1 is “a bluffer”; 1 is “sexually abnormal,” “perverted,” and “vicious.”
It will be noted that with the exception of the last child, the moral irregularities mentioned can hardly be regarded, from the psychological point of view, as essentially abnormal. It is perhaps a good rather than a bad sign for a child to be self-willed; most children “need close watching”; and a certain amount of untruthfulness in children is the rule and not the exception.
5. Social adaptability. Socially adaptable, 25; not adaptable, 2; doubtful, 4.
6. Attitude of other children. “Favorable,” “friendly,” “liked by everybody,” “much admired,” “popular,” etc., 26; “not liked,” 1; “inspires repugnance,” 1; no answer, 1.
7. Is child a leader? “Yes,” 14; “no,” or “not particularly,” 12; doubtful, 5.
8. Is play life normal? “Yes,” 26; “no,” 1; “hardly,” 1; doubt¬ ful, 3.
9. Is child spoiled or vain? “No,” 22; “yes,” 5; “somewhat,” 2; no answer, 2.
According to the above data, exceptionally intelligent children are fully as likely to be healthy as ordinary chil¬ dren; their ability is far more often general than special.
16 THE MEASUREMENT OF INTELLIGENCE
they are studious above the average, really serious faults are not common among them, they are nearly always so¬ cially adaptable, are sought after as playmates and com¬ panions, their play life is usually normal, they are leaders far oftener than other children, and notwithstanding their many really superior qualities they are seldom vain or spoiled.
It would be greatly to the advantage of such children if their superior ability were more promptly and fully recog¬ nized, and if (under proper medical supervision, of course) they were promoted as rapidly as their mental develop¬ ment would warrant. Unless they are given the grade of Work which calls forth their best efforts, they run the risk of falling into lifelong habits of submaximum efficiency. The danger in the case of such children is not over-pressure, but under-pressure.
Intelligence tests as a basis for grading. Not only in the case of retarded or exceptionally bright children, but with many others also, intelligence tests can aid in correctly placing the child in school.
The pupil who enters one school system from another is a case in point. Such a pupil nearly always suffers a loss of time. The indefensible custom is to grade the newcomei down a little, because, forsooth, the textbooks he has studied may have differed somewhat from those he is about to take up, or because the school system from which he comes may be looked upon as inferior. Teachers are too often suspicious of all other educational methods besides their own. The present treatment accorded such children, which so often does them injustice and injury, should be replaced by an intelligence test. The hour of time required for the test is a small matter in comparison with the loss of a school term by the pupils.
Indeed, it would be desirable to make all promotions on
USES OF INTELLIGENCE TESTS
17
the basis chiefly of intellectual ability. Hitherto the school has had to rely on tests of information because reliable tests of intelligence have not until recently been available. As trained Binet examiners become more plentiful, the infor¬ mation standard will have to give way to the criterion which asks merely that the child shall be able to do the work of the next higher grade. The brief intelligence test is not only more enlightening than the examination; it is also more hygienic. The school examination is often for the child a source of worry and anxiety; the mental test is an interesting and pleasant experience.
Intelligence tests for vocational fitness. The time is probably not far distant when intelligence tests will be¬ come a recognized and widely used instrument for deter¬ mining vocational fitness. Of course, it is not claimed that tests are available which will tell us unerringly exactly what one of a thousand or more occupations a given indi¬ vidual is best fitted to pursue. But when thousands of children who have been tested by the Binet scale have been followed out into the industrial world, and their success in various occupations noted, we shall know fairly definitely the vocational significance of any given degree of mental inferiority or superiority. Researches of this kind will ultimately determine the minimum “ intelligence quotient ” necessary for success in each leading occupation.
Industrial concerns doubtless suffer enormous losses from the employment of persons whose mental ability is not equal to the tasks they are expected to perform. The pres¬ ent methods of trying out new employees, transferring them to simpler and simpler jobs as their inefficiency becomes apparent, is wasteful and to a great extent unnecessary. A cheaper and more satisfactory method would be to em¬ ploy a psychologist to examine applicants for positions and to weed out the unfit. Any business employing as many
18 THE MEASUREMENT OF INTELLIGENCE
as five hundred or a thousand workers, as, for example, a large department store, could save in this way several times the salary of a well-trained psychologist.
That the industrially inefficient are often of subnormal intelligence has already been demonstrated in a number of psychological investigations. Of 150 “ hoboes ” tested under the direction of the writer by Mr. Knollin, at least 15 per cent belonged to the moron grade of mental deficiency, and almost as many more were border-line cases. To be sure, a large proportion were found perfectly normal, and a few even decidedly superior in mental ability, but the ratio of mental deficiency was ten or fifteen times as high as that holding for the general population. Several had as low as 9- or 10-year intelligence, and one had a mental level of 7 years. The industrial history of such subjects, as given by themselves, was always about what the mental level would lead us to expect — unskilled work, lack of interest in accomplishment, frequent discharge from jobs, discouragement, and finally the “ road.”
The above findings have been fully paralleled by Mr. Glenn Johnson and Professor Eleanor Rowland, of Reed College, who tested 108 unemployed charity cases in Port¬ land, Oregon. Both of these investigators made use of the Stanford revision of the Binet scale, which is especially serviceable in distinguishing the upper-grade defectives from normals.
It hardly needs to be emphasized that when charity organizations help the feeble-minded to float along in the social and industrial world, and to produce and rear children after their kind, a doubtful service is rendered. A little psychological research would aid the united chari¬ ties of any city to direct their expenditures into more profit¬ able channels than would otherwise be possible.
Other uses of intelligence tests. Another important use
USES OF INTELLIGENCE TESTS
19
of intelligence tests is in the study of the factors which influence mental development. It is desirable that we should be able to guard the child against influences which affect mental development unfavorably; but as long as these in¬ fluences have not been sifted, weighed, and measured, we have nothing but conjecture on which to base our efforts in this direction.
When we search the literature of child hygiene for reliable evidence as to the injurious effects upon mental ability of malnutrition, decayed teeth, obstructed breath¬ ing, reduced sleep, bad ventilation, insufficient exercise, etc., we are met by endless assertion painfully unsup¬ ported by demonstrated fact. We have, indeed, very little exact knowledge regarding the mental effects of any of the factors just mentioned. When standardized mental tests have come into more general use, such influences will be easy to detect wherever they are really present.
Again, the most important question of heredity is that regarding the inheritance of intelligence; but this is a prob¬ lem which cannot be attacked at all without some accurate means of identifying the thing which is the object of study. Without the use of scales for measuring intelligence we can give no better answer as to the essential difference between a genius and a fool than is to be found in legend and fiction.
Applying this to school children, it means that without such tests we cannot know to what extent a child’s mental performances are determined by environment and to what extent by heredity. Is the place of the so-called lower classes in the social and industrial scale the result of their inferior native endowment, or is their apparent inferiority merely a result of their inferior home and school training? Is genius more common among children of the educated classes than among the children of the ignorant and poor?
20 THE MEASUREMENT OF INTELLIGENCE
Are the inferior races really inferior, or are they merely unfortunate in their lack of opportunity to learn?
Only intelligence tests can answer these questions and grade the raw material with which education works. Without them we can never distinguish the results of our educational efforts with a given child from the influence of the child’s original endowment. Such tests would have told us, for example, whether the much-discussed “ wonder children,” such as the Sidis and Wiener boys and the Stoner girl, owe their precocious intellectual prowess to superior training (as their parents believe) or to superior native ability. The supposed effects upon mental develop¬ ment of new methods of mind training, which are exploited so confidently from time to time (e.g., the Montessori method and the various systems of sensory and motor training for the feeble-minded), will have to be checked up by the same kind of scientific measurement.
In all these fields intelligence tests are certain to play an ever-increasing role. With the exception of moral charac¬ ter, there is nothing as significant for a child’s future as his grade of intelligence. Even health itself is likely to have less influence in determining success in life. Although strength and swiftness have always had great survival value among the lower animals, these characteristics have long since lost their supremacy in man’s struggle for existence. For us the rule of brawn has been broken, and intelli¬ gence has become the decisive factor in success. Schools, railroads, factories, and the largest commercial concerns may be successfully managed by persons who are physically weak or even sickly. One who has intelligence constantly measures opportunities against his owm strength or weak¬ ness and adjusts himself to conditions by following those leads which promise most toward the realization of his individual possibilities.
USES OF INTELLIGENCE TESTS
21
All classes of intellects, the weakest as well as the strong¬ est, will profit by the application of their talents to tasks which are consonant with their ability. When we have learned the lessons which intelligence tests have to teach, we shall no longer blame mentally defective workmen for their industrial inefficiency, punish weak-minded children because of their inability to learn, or imprison and hang mentally defective criminals because they lacked the in¬ telligence to appreciate the ordinary codes of social conduct.
CHAPTER II
SOURCES OF ERROR IN JUDGING INTELLIGENCE
Are intelligence tests superfluous? Binet tells us that he often encountered the criticism that intelligence tests are superfluous, and that in going to so much trouble to devise his measuring scale he was forcing an open door. Those who made this criticism believed that the observant teacher or parent is able to make an offhand estimate of a child’s intelligence which is accurate enough. “ It is a stupid teacher,” said one, “ who needs a psychologist to tell her which pupils are not intelligent.” Every one who uses in¬ telligence tests meets this attitude from time to time.
This should not be surprising or discouraging. It is only natural that those who are unfamiliar with the methods of psychology should occasionally question their validity or worth, just as there are many excellent people who do not “ believe in ” vaccination against typhoid and small pox, operations for appendicitis, etc.
There is an additional reason why the applications of psychology have to overcome a good deal of conservatism and skepticism; namely, the fact that every one, whether psychologically trained or not, acquires in the ordinary experiences of life a certain degree of expertness in the observation and interpretation of mental traits. The possession of this little fund of practical working knowl¬ edge makes most people slow to admit any one’s claim to greater expertness. When the astronomer tells us the dis¬ tance to Jupiter, we accept his statement, because we
SOURCES OF ERROR IN JUDGING
23
recognize that our ordinary experience affords no basis for judgment about such matters. But every one acquires more or less facility in distinguishing the coarser differences among people in intelligence, and this half-knowledge naturally generates a certain amount of resistance to the more refined method of tests.
It should be evident, however, that we need more than the ability merely to distinguish a genius from a simple¬ ton, just as a physician needs something more than the ability to distinguish an athlete from a man dying of con¬ sumption. It is necessary to have a definite and accurate diagnosis, one which will differentiate more finely the many degrees and qualities of intelligence. Just as in the case of physical illness, we need to know not merely that the patient is sick, but also why he is sick, what organs are in¬ volved, what course the illness will run, and what physical work the patient can safely undertake, so in the case of a retarded child, we need to know the exact degree of intel¬ lectual deficiency, what mental functions are chiefly con¬ cerned in the defect, whether the deficiency is due to in¬ nate endowment, to physical illness, or to faults of educa¬ tion, and what lines of mental activity the child will be able to pursue with reasonable hope of success. In the diagnosis of a case of malnutrition, the up-to-date physician does not depend upon general symptoms, but instead makes a blood test to determine the exact number of red corpuscles per cubic millimeter of blood and the exact percentage of haemoglobin. He has learned that external appearances are often misleading. Similarly, every psychologist who is experienced in the mental examination of school children knows that his own or the teacher’s estimate of a child’s intelligence is subject to grave and frequent error.
The necessity of standards. In the first place, in order to judge an individual’s intelligence it is necessary to have
24 THE MEASUREMENT OF INTELLIGENCE
in mind some standard as to what constitutes normal in¬ telligence. This the ordinary parent or teacher does not have. In the case of school children, for example, each pupil is judged with reference to the average intelligence of the class. But the teacher has no means of knowing whether the average for her class is above, equal to, or below that for children in general. Her standard may be too high, too low, vague, mechanical, or fragmentary. The same, of course, holds in the case of parents or any one else attempting to estimate intelligence on the basis of common observation.
The intelligence of retarded children usually over¬ estimated. One of the most common errors made by the teacher is to overestimate the intelligence of the over-age pupil. This is because she fails to take account of age dif¬ ferences and estimates intelligence on the basis of the child’s school performance in the grade where he happens to be located. She tends to overlook the fact that quality of school work is no index of intelligence unless age is taken into account. The question should be, not, “ Is this child doing his school work well? ” but rather, “ In what school grade should a child of this age be able to do satisfactory work? ” A high-grade imbecile may do average work in the first grade, and a high-grade moron average work in the third or fourth grade, provided only they are sufficiently over-age for the grade in question.
Our experience in testing children for segregation in special classes has time and again brought this fallacy of teachers to our attention. We have often found one or more feeble-minded children in a class after the teacher had confidently asserted that there was not a single exception¬ ally dull child present. In every case where there has been opportunity to follow the later school progress of such a child the validity of the intelligence test has been fully confirmed.
SOURCES OF ERROR IN JUDGING
25
The following are typical examples of the neglect of teach¬ ers to take the age factor into account when estimating the intelligence of the over-age child : —
A. R. Girl, age 11; in low second grade. She was able to do the work of this grade, not well, but passably. The teacher’s judgment as to this child’s intelligence was “dull but not defective.” What the teacher overlooked was the fact that she had judged the child by a 7-year standard, and that, mstead of only being able to do the work of the second grade indifferently, a child of this age should have been equal to the work of the fifth grade. In reality, A. R. is definitely feeble-minded. Although she is from a home of average culture, is 11 years old, and has attended school five years, she has barely the intelligence of the average child of six years.
D. C. Boy, age 17; in fifth grade. His teacher knew that he was dull, but had not thought of him as belonging to the class of feeble¬ minded. She had judged this boy by the 11-year standard and had perhaps been further misled by his normal appearance and exceptionally satisfactory behavior. The Binet test quickly showed that he had a mental level of approximately 9 years. There is little probability that his comprehension will ever surpass that of the average 10-year-old.
R. A. Boy, age 17; mental age 11; sixth grade; school work “ nearly average teacher’s estimate of intelligence “average.” Test plainly shows this child to be a high-grade moron, or border-liner at best. Had attended school regularly 11 years and had made 6 grades. Teacher had compared child with his 12-year-old class¬ mates.
H. A. Boy, age If; mental age 9-6; low fourth grade; school work “inferior”; teacher’s estimate of intelligence “average.” The teacher blamed the inferior quality of school work to “bad home environ¬ ment.” As a matter of fact, the boy’s father is feeble-minded and the normality of the mother is questionable. An older brother is in a reform school. We are perfectly safe in predicting that this boy will not complete the eighth grade even if he attends school till he is 21 years of age.
F. I. Boy, age 12-11; mental age 9-1; third grade; school work “average”; teacher’s estimate of intelligence “average” ; social en¬ vironment “average”; health good and attendance regular. Intelli¬ gence and school success are what we should expect of an average 8-year-old.
26 THE MEASUREMENT OF INTELLIGENCE
D. A. Boy, age 12; mental age 9-2; third grade; school work “in¬ ferior”; teacher's estimate of intelligence “average.” Teacher im¬ putes inferior school work to “absence from school and lack of interest in books”; we have yet to find a child with a mental age 25 per cent below chronological age who was particularly inter¬ ested in books or enthusiastic about school.
C. U. Girl, age 10; mental age 7-8; second grade; school work “average”; teacher’s estimate of intelligence “average.” Teacher blames adenoids and bad teeth for retardation. No doubt of child’s mental deficiency.
P. I. Girl, age 8-10; mental age 6-7; has been in first grade 2^/2 years; school work “average”; teacher’s estimate of intelligence “aver¬ age.” The mother and one brother of this girl are both feeble¬ minded.
II. 0. Girl, age 7-10; mental age 5-2; first grade for 2 years; school work “inferior” ; teacher’s estimate of intelligence “average.” The teacher nevertheless adds, “This child is not normal, but her ability to respond to drill shows that she has intelligence.” It is of course true that even feeble-minded children of 5-year intelli¬ gence are able to profit a little from drill. Their weakness comes to light in their mability to perform higher types of mental activity.
The intelligence of superior children usually underesti¬ mated. We have already mentioned the frequent failure of teachers and parents to recognize superior ability.1 The fal¬ lacy here is again largely due to the neglect of the age factor, but the resulting error is in the opposite direction from that set forth above. The superior child is likely to be a year or two younger than the average child of his grade, and is ac¬ cordingly judged by a standard which is too high. The following are illustrations : —
M. L. Girl, age 11-2; mental age “average adult” (16); sixth grade; school work “superior” ; teacher’s estimate of intelligence “average.” Teacher credits superior school work to “unusual home advantages.” Father a college professor. The teacher con¬ siders the child accelerated in school. In reality she ought to be in the second year of high school instead of in the sixth grade.
1 See p. 13 jf.
SOURCES OF ERROR IN JUDGING
27
H. A. Boy, aye 11; mental age If; sixth grade; school worlc “aver¬ age”; teacher's estimate of intelligence “average.” According to the supplementary information the boy is “wonderfully attentive,” “studious,” and possessed of “all-round ability.” The estimate of “average intelligence” was probably the result of comparing him with classmates who averaged about a year older.
K. R. Girl, age 6—1; mental age 8-5; second grade; school work “average”; teacher’s estimate of intelligence “superior”; social en¬ vironment “average.” Is it not evident that a child from ordinary social environment, who does work of average quality in the second grade when barely 6 years of age, should be judged “very superior” rather than merely “superior” in intelligence? The intelligence quotient of this girl is 140, which is not reached by more than one child in two hundred.
S. A. Boy, age 8-10; mental age 10-9; fourth grade; school work “average” ; teacher’s estimate of intelligence “average.” Teacher attributed school acceleration to “studiousness” and “delight in school work.” It would be more reasonable to infer that these traits are indications of unusually superior intelligence.
Other fallacies in the estimation of intelligence. An¬ other source of error in the teacher’s judgment comes from the difficulty in distinguishing genuine dullness from the mental condition which results sometimes from unfavorable social environment or lack of training.
V. P. Boy, age 7. Had attended school one year and had profited very little from the instruction. He had learned to read very little, spoke chiefly in monosyllables, and seemed “ queer.” The teacher suspected his intelligence and asked for a mental examina¬ tion. The Binet test showed that except for vocabulary, which was unusually low, there was practically no mental retardation. In¬ quiry disclosed the fact that the boy’s parents were uneducated deaf-mutes, and that the boy had associated little with other children. Four years later this boy was doing fairly well in school, though a year retarded because of his unfavorable home environ¬ ment.
X. Y. Boy, age 10. Son of a successful business man, he was barely able to read in the second reader. The Binet test revealed an intelligence level which was absolutely normal. The boy was
28 THE MEASUREMENT OF INTELLIGENCE
removed to a special class where he could receive individual at¬ tention, and two years later was found doing good work in a regu¬ lar class of the fifth grade. His bad beginning seemed to have been due to an unfavorable attitude toward school work, due in turn to lack of discipline in the home, and to the fact that because of the father’s frequent change of business headquarters the boy had never attended one school longer than three months.
Another source of error in judging intelligence from com¬ mon observation is the tendency to overestimate the in¬ telligence of the sprightly, talkative, sanguine child, and to underestimate the intelligence of the child who is less emotional, reacts slowly, and talks little. One occasion¬ ally finds a feeble-minded adult, perhaps of only 9- or 10- year intelligence, whose verbal fluency, mental liveliness, and self-confidence would mislead the offhand judgment of even the psychologist. One individual of this type, a bor¬ der-line case at best, was accustomed to harangue street audiences and had served as “ major ” in “ Kelly’s Army,” a horde of several hundred unemployed men who a few years ago organized and started to march from San Francisco to Washington.
Binet’s questionnaire on teachers’ methods of judging intelligence.1 Aroused by the skepticism so often shown toward his test method, Binet decided to make a little study of the methods by which teachers are accustomed to arrive at a judgment as to a child’s intelligence. Accord¬ ingly, through the cooperation of the director of elementary education in Paris, he secured answers from a number of teachers to the following questions : —
1. By what means do you judge the intelligence of your pupils?
2. How often have you been deceived in your judgments?
About 40 replies were received. Most of the answers to the first question were vague, one-sided, “ verbal,” or
1 See p. 109 jf. of reference 2, at end of this book
SOURCES OF ERROR IN JUDGING
29
bookish. Only a few showed much psychological dis¬ crimination as to what intelligence is and what its symp¬ toms are. There was a very general tendency to judge intelligence by success in one or more of the school studies. Some thought that ability to master arithmetic was a sure criterion. Others were influenced almost entirely by the pupil’s ability to read. One teacher said that the child who can “ read so expressively as to make you feel the punc¬ tuation ” is certainly intelligent, an observation which is rather good, as far as it goes. A few judged intelligence by the pupil’s knowledge of such subjects as history and geography, which, as Binet points out, is to confound in¬ telligence with the ability to memorize. “ Memory,” says Binet, is a “ great simulator of intelligence.” It is a wise teacher who is not deceived by it. Only a small minority mentioned resourcefulness in play, capacity to adjust to practical situations, or any other out-of-school criteria.
Some suggested asking the pupil such questions as the following: —
“Why do you love your parents?” “If it takes three persons seven hours to do a piece of work, would it take seven persons any longer?” “Which would you rather have, a fourth of a pie, or a half of a half?” “Which is heavier, a pound of feathers or a pound of lead?” “If you had twenty cents what would you do with it?”
A great many based their judgment mainly on the gen¬ eral appearance of the face and eyes. An “ active ” or “ passive ” expression of the eyes was looked upon as es¬ pecially significant. One teacher thought that a mere “ glance of the eye ” was sufficient to display the grade of intelligence. If the eyes are penetrating, reflective, or show curiosity, the child must be intelligent; if they are heavy and expressionless, he must be dull. The mobility of coun¬ tenance came in for frequent mention, also the shape of the head.
SO THE MEASUREMENT OF INTELLIGENCE
No one will deny that intelligence displays itself to a greater or less extent in the features; but how, asks Binet, are we going to standardize a “ glance of the eye ” or an “ expression of curiosity ” so that it will serve as an exact measure of intelligence?
The fact is, the more one sees of feeble-minded children, the less reliance one comes to place upon facial expression as a sign of intelligence. Some children who are only slightly backward have the general appearance of low-grade im¬ beciles. On the other hand, not a few who are distinctly feeble-minded are pretty and attractive. With many such children a ready smile takes the place of comprehension. If the smile is rather sweet and sympathetic, as is often the case, the observer is almost sure to be deceived.
As regards the shape of the head, peculiar conformation of the ears, and other “ stigmata,” science long ago demon¬ strated that these are ordinarily of little or no significance.
In reply to the second question, some teachers stated that they never made a mistake, while others admitted failure in one case out of three. Still others said, “ Once in ten years,” “ once in twenty years,” “ once in a thousand times,” etc.
As Binet remarks, the answers to this question are not very enlightening. In the first place, the teacher as a rule loses sight of the pupil when he has passed from her care, and seldom has opportunity of finding out whether his later success belies her judgment or confirms it. Errors go undiscovered for the simple reason that there is no op¬ portunity to check them up. In the second place, her esti¬ mate is so rough that an error must be very great in order to have any meaning. If I say that a man is six feet and two inches tall, it is easy enough to apply a measuring stick and prove the correctness or incorrectness of my as¬ sertion. But if I say simply that the man is “ rather tall,”
SOURCES OF ERROR IN JUDGING
31
or “ very tall,” the error must be very extreme before we can expose it, particularly since the estimate can itself be checked up only by observation and not by controlled ex¬ periment.
The teachers’ answers seem to justify three conclusions: —
1. Teachers do not have a very definite idea of what constitutes intelligence. They tend to confuse it variously with capacity for memorizing, facility in reading, ability to master arithmetic, etc. On the whole, their standard is too academic. They fail to appreciate the one-sidedness of the school’s demands upon intelligence.
In a quaintly humorous passage discussing this tendency, Binet characterizes the child in a class as denature, a French word which we may translate (though rather too literally) as “ denatured.” Too often this “ denatured ” child of the classroom is the only child the teacher knows.
2. In judging intelligence teachers are too easily de¬ ceived by a sprightly attitude, a sympathetic expression, a glance of the eye, or a chance “ bump ” on the head.
3. Although a few teachers seem to realize the many possibilities of error, the majority show rather undue con¬ fidence in the accuracy of their judgment.
Binet’s experiment on how teachers test intelligence.1 Finally, Binet had three teachers come to his laboratory to judge the intelligence of children whom they had never seen before. Each spent an afternoon in the laboratory and examined five pupils. In each case the teacher was left free to arrive at a conclusion in her own way. Binet, who remained in the room and took notes, recounts with play¬ ful humor how the teachers were unavoidably compelled to resort to the much-abused test method, although their attempts at using it were sometimes, from the psycholo¬ gist’s point of view, amusingly clumsy.
1 See p. 182 jf. of reference 2 at end of this book.
32 THE MEASUREMENT OF INTELLIGENCE
One teacher, for example, questioned the children about some canals and sluices which were in the vicinity, asking what their purpose was and how they worked. Another showed the children some pretty pictures, which she had brought with her for the purpose, and asked questions about them. Showing the picture of a garret, she asked how a garret differs from an ordinary room. One teacher asked whether in building a factory it was best to have the walls thick or thin. As King Edward had just died, another teacher questioned the children about the details of this event, in order to find out whether they were in the habit of reading the newspapers, or understood the things they heard others read. Other questions related to the names of the streets in the neighborhood, the road one should take to reach a certain point in the vicinity, etc. Binet notes that many of the questions were special, and were only applicable with the children of this particular school.
The method of proposing the questions and judging the responses was also at fault. The teachers did not adhere consistently to any definite formula in giving a particular test to the different children. Instead, the questions were materially altered from time to time. One teacher scored the identical response differently for two children, giving one child more credit than the other because she had already judged his intelligence to be superior. In several cases the examination was needlessly delayed in order to instruct the child in what he did not know.
The examination ended, quite properly for a teacher’s examination, with questions about history, literature, the metric system, etc., and with the recitation of a fable.
A comparison of the results showed hardly any agree¬ ment among the estimates of the three teachers. When questioned about the standard that had been taken in ar¬ riving at their conclusions, one teacher said she had taken
SOURCES OF ERROR IN JUDGING
the answers of the first pupil as a point of departure, and that she had judged the other pupils by this one. Another judged all the children by a child of her acquaintance whom she knew to be intelligent. This was, of course, an unsafe method, because no one could say how the child taken as an ideal would have responded to the tests used with the five children.
In summarizing the result of his little experiment, Binet points out that the teachers employed, as if by instinct, the very method which he himself recommends. In using it, however, they made numerous errors. Their questions were often needlessly long. Several were “ dilemma questions,” that is, answerable by yes or no. In such cases chance alone will cause fifty per cent of the answers to be correct. Some of the questions were merely tests of school knowledge. Others were entirely special, usable only with the children of this particular school on this particular day. Not all of the questions were put in the same terms, and a given re¬ sponse did not always receive the same score. When the chil¬ dren responded incorrectly or incompletely, they were often given help, but not always to the same extent. In other words, says Binet, it was evident that “ the teachers em¬ ployed veiy awkwardly a very excellent method.”
The above remark is as pertinent as it is expressive. As the statement implies, the test method is but a refine¬ ment and standardization cf the common-sense approach. Binet remarks that most people who inquire into his method of measuring intelligence do so expecting to find something very surprising and mysterious; and on seeing how much it resembles the methods which common sense employs in ordinary life, they heave a sigh of disappoint¬ ment and say, “ Is that all? ” Binet reminds us that the difference between the scientific and unscientific way of doing a thing is not necessarily a difference in the nature
34 THE MEASUREMENT OF INTELLIGENCE
of the method; it is often merely a difference in exactness. Science does the thing better, because it does it more accurately.
It was of course not the purpose of Binet to cast a slur upon the good sense and judgment of teachers. The teach¬ ers who took part in the little experiment described above were Binet’s personal friends. The errors he points out in his entertaining and good-humored account of the experi¬ ment are inherent in the situation. They are the kind of errors which any person, however discriminating and ob¬ servant, is likely to make in estimating the intelligence of a subject without the use of standardized tests.
It is the writer’s experience that the teacher’s estimate of a child’s intelligence is much more reliable than that of the average parent; more accurate even than that of the physician who has not had psychological training.
Indeed, it is an exceptional school physician who is able to give any very valuable assistance to teachers in the classification of mentally exceptional children for special pedagogical treatment.
This is only to be expected, for the physician has or¬ dinarily had much less instruction in psychology than the teacher, and of course infinitely less experience in judging the mental performances of children. Even if graduated from a first-rank medical school, the instruction he has received in the important subject of mental deficiency has probably been less adequate than that given to the students of a standard normal school. As a rule, the doctor has no equipment or special fitness which gives him any advantage over the teacher in acquiring facility in the use of intelligence tests.
As for parents, it would of course be unreasonable to expect from them a very accurate judgment regarding the mental peculiarities of their children. The difficulty is
SOURCES OF ERROR IN JUDGING
35
not simply that which comes from lack of special train¬ ing. The presence of parental affection renders impartial judgment impossible. Still more serious are the effects of habituation to the child’s mental traits. As a result of such habituation the most intelligent parent tends to de¬ velop an unfortunate blindness to all sorts of abnormal¬ ities which exist in his own children.
The only way of escape from the fallacies we have men¬ tioned lies in the use of some kind of refined psychological procedure. Binet testing is destined to become universally known and practiced in schools, prisons, reformatories, charity stations, orphan asylums, and even ordinary homes, for the same reason that Babcock testing has become uni¬ versal in dairying. Each is indispensable to its purpose.
CHAPTER III
DESCRIPTION OF THE BINET-SIMON METHOD
Essential nature of the scale. The Binet scale is made up of an extended series of tests in the nature of “ stunts,” or problems, success in which demands the exercise of in¬ telligence. As left by Binet, the scale consists of 54 tests, so graded in difficulty that the easiest lie well within the range of normal 3-year-old children, while the hardest tax the intelligence of the average adult. The problems are designed primarily to test native intelligence, not school knowledge or home training. They try to answer the ques¬ tion, “ How intelligent is this child? ” How much the child has learned is of significance only in so far as it throws light on his ability to learn more.
Binet fully appreciated the fact that intelligence is not homogeneous, that it has many aspects, and that no one kind of test will display it adequately. He therefore as¬ sembled for his intelligence scale tests of many different types, some of them designed to display differences of memory, others differences in power to reason, ability to compare, power of comprehension, time orientation, facil¬ ity in the use of number concepts, power to combine ideas into a meaningful whole, the maturity of appercep¬ tion, wealth of ideas, knowledge of common objects, etc.
How the scale was derived. The tests were arranged in order of difficulty, as found by trying them upon some 200 normal children of different ages from 3 to 15 years. It was found, for illustration, that a certain test was passed
THE BINET-SIMON METHOD
37
by only a very small proportion of the younger children, say the 5-year-olds, and that the number passing this test increased rapidly in the succeeding years until by the age of 7 or 8 years, let us say, practically all the children were successful. If, in our supposed case, the test was passed by about two thirds to three fourths of the normal children aged 7 years, it was considered by Binet a test of 7-year intelligence. In like manner, a test passed by 65 to 75 per cent of the normal 9-year-olds was considered a test of 9- year intelligence, and so on. By trying out many different tests in this way it was possible to secure five tests to repre¬ sent each age from 3 to 10 years (excepting age 4, which has only four tests), five for age 12, five for 15, and five for adults, making 54 tests in all.
List of tests. The following is the list of tests as arranged by Binet in 1911, shortly before his untimely death: —
Age 3:
1. Points to nose, eyes, and mouth.
2. Repeats two digits.
3. Enumerates objects in a picture.
4. Gives family name.
5. Repeats a sentence of six syllables.
Age 4:
1. Gives his sex.
2. Names key, knife, and penny.
3. Repeats three digits.
4. Compares two lines.
Age 5:
1. Compares two weights.
2. Copies a square.
3. Repeats a sentence of ten syllables.
4. Counts four pennies.
5. Unites the halves of a divided rectangle.
Age 6:
1. Distinguishes between morning and afternoon.
2. Defines familiar words in terms of use.
38 THE MEASUREMENT OF INTELLIGENCE
3. Copies a diamond.
4. Counts thirteen pennies.
5. Distinguishes pictures of ugly and pretty faces.
Age 7:
1. Shows right hand and left ear.
2. Describes a picture.
S. Executes three commissions, given simultaneously.
4. Counts the value of six sous, three of which are double.
5. Names four cardinal colors.
Age 8:
1. Compares two objects from memory.
2. Counts from 20 to 0.
3. Notes omissions from pictures.
4. Gives day and date.
5. Repeats five digits.
Age 9:
1. Gives change from twenty sous.
2. Defines familiar words in terms superior to use.
3. Recognizes all the pieces of money.
4. Names the months of the year, in order.
5. Answers easy “comprehension questions.”
Age 10:
1. Arranges five blocks in order of weight.
2. Copies drawings from memory.
3. Criticizes absurd statements.
4. Answers difficult “comprehension questions.”
5. Uses three given words in not more than two sentences.
Age 12:
1. Resists suggestion.
2. Composes one sentence containing three given words.
3. Names sixty words in three minutes.
4. Defines certain abstract words.
5. Discovers the sense of a disarranged sentence.
Age 15:
1. Repeats seven digits.
2. Finds three rhymes for a given word.
3. Repeats a sentence of twenty-six syllables.
4. Interprets pictures.
5. Interprets given facts.
THE BINET-SIMON METHOD
39
Adult:
1. Solves the paper-cutting test.
2. Rearranges a triangle in imagination.
3. Gives differences between pairs of abstract terms.
4. Gives three differences between a president and a king.
5. Gives the main thought of a selection which he has heard read.
It should be emphasized that merely to name the tests in this way gives little idea of their nature and meaning, and tells nothing about Binet’s method of conducting the 54 experiments. In order to use the tests intelligently it is necessary to acquaint one’s self thoroughly with the pur¬ pose of each test, its correct procedure, and the psychologi¬ cal interpretation of different types of response.1
In fairness to Binet, it should also be borne in mind that the scale of tests was only a rough approximation to the ideal which the author had set himself to realize. Had his life been spared a few years longer, he would doubtless have carried the method much nearer perfection.
How the scale is used. By means of the Binet tests we can judge the intelligence of a given individual by compari¬ son with standards of intellectual performance for normal children of different ages. In order to make the comparison it is only necessary to begin the examination of the subject at a point in the scale where all the tests are passed suc¬ cessfully, and to continue up the scale until no more suc¬ cesses are possible. Then we compare our subject’s per¬ formances with the standard for normal children of the same age, and note the amount of acceleration or retarda¬ tion.
Let us suppose the subject being tested is 9 years of age. If he goes as far in the tests as normal 9-year-old children ordinarily go, we can say that the child has a “ mental
1 See Part II of this volume, and References 1 and 29, for discussion and interpretation of the individual tests.
40 THE MEASUREMENT OF INTELLIGENCE
age ” of 9 years, which in this case is normal (our child being 9 years of age). If he goes only as far as normal 8-year-old children ordinarily go, we say that his “ mental age ” is 8 years. In like manner, a mentally defective child of 9 years may have a “ mental age ” of only 4 years, or a young genius of 9 years may have a mental age of 12 or 13 years.
Special characteristics of the Binet-Simon method.
Psychologists had experimented with intelligence tests for at least twenty years before the Binet scale made its ap¬ pearance. The question naturally suggests itself why Binet should have been successful in a field where previous efforts had been for the most part futile. The answer to this ques¬ tion is found in three essential differences between Binet’s method and those formerly employed.
1. The use of age standards. Binet was the first to utilize the idea of age standards, or norms, in the measurement of intelligence. It will be understood, of course, that Binet did not set out to invent tests of 10-year intelligence, 6- year intelligence, etc. Instead, as already explained, he began with a series of tests ranging from very easy to very difficult, and by trying these tests on children of different ages and noting the percentages of successes in the various years, he was able to locate them (approximately) in the years where they belonged.
This plan has the great advantage of giving us standards which are easily grasped. To say, for illustration, that a given subject has a grade of intelligence equal to that of the average child of 8 years is a statement whose general im¬ port does not need to be explained. Previous investigators had worked with subjects the degree of whose intelligence was unknown, and with tests the difficulty of which was equally unknown. An immense amount of ingenuity was spent in devising tests which were used in such a way as to
THE BINET-SIMON METHOD
41
preclude any very meaningful interpretation of the re¬ sponses.
The Binet method enables us to characterize the in¬ telligence of a child in a far more definite way than had hitherto been possible. Current descriptive terms like “bright,” “moderately bright,” “dull,” “very dull,” “ feeble-minded,” etc., have had no universally accepted meaning. A child who is designated by one person as “ moderately bright ” may be called “ very bright ” by another person. The degree of intelligence which one calls “ moderate dullness,” another may call “extreme dullness,” etc. But every one knows what is meant by the term 8-year mentality, 4-year mentality, etc., even if he is not able to define these grades of intelligence in psychological terms; and by ascertaining experimentally what intellectual tasks children of different ages can perform, we are, of course, able to make our age standards as definite as we please.
Why should a device so simple have waited so long for a discoverer? We do not know. It is of a class with many other unaccountable mysteries in the development of scientific method. Apparently the idea of an age-grade method, as this is called, did not come to Binet himself until he had experimented with intelligence tests for some, fifteen years. At least his first provisional scale, published in 1905, was not made up according to the age-grade plan. It consisted merely of 30 tests, arranged roughly in order of difficulty. Although Binet nowhere gives any account of the steps by which this crude and ungraded scale was trans¬ formed into the relatively complete age-grade scale of 1908, we can infer that the original and ingenious idea of utiliz¬ ing age norms was suggested by the data collected with the 1905 scale. However the discovery was made, it ranks, per¬ haps, from the practical point of view, as the most important in all the history of psychology.
42 THE MEASUREMENT OF INTELLIGENCE
2. The hind of mental functions brought into 'play. In the second place, the Binet tests differ from most of the earlier attempts in that they are designed to test the higher and more complex mental processes, instead of the simpler and more elementary ones. Hence they set problems for the reasoning powers and ingenuity, provoke judgments about abstract matters, etc., instead of attempting to measure sensory discrimination, mere retentiveness, rapidity of reaction, and the like. Psychologists had generally con¬ sidered the higher processes too complex to be measured directly, and accordingly sought to get at them indirectly by correlating supposed intelligence with simpler processes which could readily be measured, such as reaction time, rapidity of tapping, discrimination of tones and colors, etc. While they were disputing over their contradictory findings in this line of exploration, Binet went directly to the point and succeeded where they had failed.
It is now generally admitted by psychologists that higher intelligence is little concerned in such elementary processes as those mentioned above. Many of the animals have keen sensory discrimination. Feeble-minded children, unless of very low grade, do not differ very markedly from normal children in sensitivity of the skin, visual acuity, simple reaction time, type of imagery, etc. But in power of com¬ prehension, abstraction, and ability to direct thought, in the nature of the associative processes, in amount of information possessed, and in spontaneity of attention, they differ enormously.
3. Binet would test “ general intelligence.” Finally, Binet’s success was largely due to his abandonment of the older “ faculty psychology ” which, far from being defunct, had really given direction to most of the earlier work with mental tests. Where others had attempted to measure mem¬ ory, attention, sense discrimination, etc., as separate facui-
THE BINET-SIMON METHOD
43
ties or functions, Binet undertook to ascertain the general level of intelligence. Others had thought the task easier of accomplishment by measuring each division or aspect of intelligence separately, and summating the results. Binet, too, began in this way, and it was only after years of experi¬ mentation by the usual methods that he finally broke away from them and undertook, so to speak, to triangulate the height of his tower without first getting the dimensions of the individual stones which made it up.
The assumption that it is easier to measure a part, or one aspect, of intelligence than all of it, is fallacious in that the parts are not separate parts and cannot be separated by any refinement of experiment. They are interwoven and intertwined. Each ramifies everywhere and appears in all other functions. The analogy of the stones of the tower does not really apply. Memory, for example, cannot be tested separately from attention, or sense-discrimination sepa¬ rately from the associative processes. After many vain at¬ tempts to disentangle the various intellective functions, Binet decided to test their combined functional capacity without any pretense of measuring the exact contribution of each to the total product. It is hardly too much to say that intelligence tests have been successful just to the extent to which they have been guided by this aim.
Memory, attention, imagination, etc., are terms of “ structural psychology.” Binet ’s psychology is dynamic. He conceives intelligence as the sum total of those thought processes which consist in mental adaptation. This adapta¬ tion is not explicable in terms of the old mental “ faculties.” No one of these can explain a single thought process, for such process always involves the participation of many functions whose separate roles are impossible to distin¬ guish accurately. Instead of measuring the intensity of various mental states (psycho-physics), it is more enlight-
44 THE MEASUREMENT OF INTELLIGENCE
ening to measure their combined effect on adaptation. Using a biological comparison, Binet says the old “ faculties ” correspond to the separate tissues of an animal or plant, while his own “ scheme of thought ” corresponds to the functioning organ itself. For Binet, psychology is the science of behavior.
Binet’s conception of general intelligence. In devising tests of intelligence it is, of course, necessary to be guided by some assumption, or assumptions, regarding the nature of intelligence. To adopt any other course is to depend for success upon happy chance.
However, it is impossible to arrive at a final definition of intelligence on the basis of a-priori considerations alone. To demand, as critics of the Binet method have sometimes done, that one who would measure intelligence should first present a complete definition of it, is quite unreasonable. As Stern points out, electrical currents were measured long before their nature was well understood. Similar illustra¬ tions could be drawn from the processes involved in chem¬ istry, physiology, and other sciences. In the case of in¬ telligence it may be truthfully said that no adequate defi¬ nition can possibly be framed which is not based primarily on the symptoms empirically brought to light by the test method. The best that can be done in advance of such data is to make tentative assumptions as to the probable nature of intelligence, and then to subject these assumptions to tests which will show their correctness or incorrectness. New hypotheses can then be framed for further trial, and thus gradually we shall be led to a conception of intelli¬ gence which will be meaningful and in harmony with all the ascertainable facts
Such was the method of Binet. Only those unacquainted with Binet’s more than fifteen years of labor preceding the publication of his intelligence scale would think of accus-
THE BINET-SIMON METHOD
45
ing him of making no effort to analyze the mental proc¬ esses which his tests bring into play. It is true that many of Binet’s earlier assumptions proved untenable, and in this event he was always ready, with exceptional candor and intellectual plasticity, to acknowledge his error and to plan a new line of attack.
Binet’s conception of intelligence emphasizes three char¬ acteristics of the thought process: (1) Its tendency to take and maintain a definite direction; (2) the capacity to make adaptations for the purpose of attaining a desired end; and (3) the power of auto-criticism.1
How these three aspects of intelligence enter into the performances with various tests of the scale is set forth from time to time in our directions for giving and interpreting the individual tests.2 An illustration which may be given here is that of the “ patience test,” or uniting the disarranged parts of a divided rectangle. As described by Binet, this operation has the following elements: “ (1) to keep in mind the end to be attained, that is to say, the figure to be formed; (2) to try different combinations under the influ¬ ence of this directing idea, which guides the efforts of the subject even though he may not be conscious of the fact; and (3) to judge the combination which has beep, made, to compare it with the model, and to decide whether it is the correct one.”
Much the same processes are called for in many other of the Binet tests, particularly those of arranging weights, rearranging dissected sentences, drawing a diamond or square from copy, finding a sentence containing three given words, counting backwards, etc.
1 See Binet and Simon: “ L’intelligence des imbeciles,” in L’ Annie Psy- chologique (1909), pp. 1-147. The last division of this article is devoted to a discussion of the essential nature of the higher thought processes, and is a wonderful example of that keen psychological analysis in which Binet was so gifted. * See especially pages 162 and 238.
46 THE MEASUREMENT OF INTELLIGENCE
However, an examination of the scale will show that the choice of tests was not guided entirely by any single for¬ mula as to the nature of intelligence. Binet’s approach was a many-sided one. The scale includes tests of time orienta¬ tion, of three or four kinds of memory, of apperception, of language comprehension, of knowledge about common ob¬ jects, of free association, of number mastery, of construc¬ tive imagination, and of ability to compare concepts, to see contradictions, to combine fragments into a unitary whole, to comprehend abstract terms, and to meet novel situations.
Other conceptions of intelligence. It is interesting to compare Binet’s conception of intelligence with the defini¬ tions which have been offered by other psychologists. Ac¬ cording to Ebbinghaus, for example, the essence of intelli¬ gence lies in comprehending together in a unitary, meaning¬ ful whole, impressions and associations which are more or less independent, heterogeneous, or even partly contra¬ dictory. “ Intellectual ability consists in the elaboration of a whole into its worth and meaning by means of many- sided combination, correction, and completion of numerous kindred associations. ... It is a combination activity .”
Meumann offers a twofold definition. From the psy¬ chological point of view, intelligence is the power of in¬ dependent and creative elaboration of new products out of the material given by memory and the senses. From the practical point of view, it involves the ability to avoid errors, to surmount difficulties, and to adjust to environ¬ ment.
Stern defines intelligence as “ the general capacity of an individual consciously to adjust his thinking to new re¬ quirements : it is general adaptability to new problems and conditions of life.”
Spearman, Hart, and others of the English school define
THE BINET-SIMON METHOD
47
intelligence as a “ common central factor ” which partici¬ pates in all sorts of special mental activities. This factor is explained in terms of a psycho-physiological hypothesis of “ cortex energy,” “ cerebral plasticity,” etc.
The above definitions are only to a slight extent con¬ tradictory or inharmonious. They differ mainly in point of view or in the location of the emphasis. Each expresses a part of the truth, and none all of it. It will be evident that the conception of Binet is broad enough to include the most important elements in each of the other definitions quoted.
Guiding principles in choice and arrangement of tests.
In choosing his tests Binet was guided by the conception of intelligence which we have set forth above. Tests were de¬ vised which would presumably bring into play the various mental processes thought to be concerned in intelligence, and then these tests were tried out on normal children of different ages. If the percentage of passes for a given test increased but little or not at all in going from younger to older children this test was discarded. On the other hand, if the proportion of passes increased rapidly with age, and if children of a given age, who on other grounds were known to be bright, passed more frequently than children of the same age who were known to be dull, then the test was judged a satisfactory test of intelligence. As we have shown elsewhere,1 practically all of Binet’s tests fulfill these re¬ quirements reasonably well, a fact which bears eloquent testimony to the keen psychological insight of their author.
In arranging the tests into a system Binet’s guiding prin¬ ciple was to find an arrangement of the tests which would cause an average child of any given age to test “ at age ”; that is, the average 5-year-old must show a mental age of 5 years, the average 8-year-old a mental age of 8 years, etc.
1 See p. 55.
48 THE MEASUREMENT OF INTELLIGENCE
In order to secure this result Binet found that his data seemed to require the location of an individual test in that year where it was passed by about two thirds to three fourths of unselected children.
It was in the assembling of the tests that the most serious faults of the scale had their origin. Further investigation has shown that a great many of the tests were misplaced as much as one year, and several of them two years. On the whole, the scale as Binet left it was decidedly too easy in the lower ranges, and too difficult in the upper. As a result, the average child of 5 years was caused to test at not far from 6 years, the average child of 12 years not far from 11. In the Stanford revision an effort has been made to correct this fault, along with certain other generally recognized imperfections.
Some avowed limitations of the Binet tests. The Binet tests have often been criticized for their unfitness to perform certain services which in reality they were never meant to render. This is unfair. We cannot make a just evaluation of the scale without bearing in mind its avowed limita¬ tions.
For example, the scale does not pretend to measure the entire mentality of the subject, but only general intelli¬ gence. There is no pretense of testing the emotions or the will beyond the extent to which these naturally display themselves in the tests of intelligence. The scale was not designed as a tool for the analysis of those emotional or volitional aberrations which are concerned in such mental disorders as hysteria, insanity, etc. These conditions do not present a progressive reduction of intelligence to the in¬ fantile level, and in most of them other factors besides in¬ telligence play an important role. Moreover, even in the normal individual the fruitfulness of intelligence, the direc¬ tion in which it shall be applied, and its methods of work
THE BINET-SIMON METHOD
49
are to a certain extent determined by the extraneous fac¬ tors of emotion and volition.
It should, nevertheless, be pointed out that defects of intelligence, in a large majority of cases, also involve dis¬ turbances of the emotional and volitional functions. We do not expect to find perfectly normal emotions or will power of average strength coupled with marked intellectual deficiency, and as a matter of fact such a combination is rare indeed. In the course of an examination with the Binet tests, the experienced clinical psychologist is able to gain considerable insight into the subject’s emotional and voli¬ tional equipment, even though the method was designed primarily for another purpose.
A second misunderstanding can be avoided by remem¬ bering that the Binet scale does not pretend to bring to light the idiosyncrasies of special talent, but only to measure the general level of intelligence. It cannot be used for the discovery of exceptional ability in drawing, painting, music, mathematics, oratory, salesmanship, etc., because no ef¬ fort is made to explore the processes underlying these abil¬ ities. It can, therefore, never serve as a detailed chart for the vocational guidance of children, telling us which will succeed in business, which in art, which in medicine, etc. It is not a new kind of phrenology. At the same time, as we have already pointed out, it is capable of bounding roughly the vocational territory in which an indi¬ vidual’s intelligence will probably permit success, nothing else preventing.1
In the third place, it must not be supposed that the scale can be used as a complete pedagogical guide. Although intelligence tests furnish data of the greatest significance for pedagogical procedure, they do not suggest the appro¬ priate educational methods in detail. These will have to
1 See p. 17.
50 THE MEASUREMENT OF INTELLIGENCE
be worked out in a practical way for the various grades of intelligence, and at great cost of labor and patience.
Finally, in arriving at an estimate of a subject’s grade of intelligence and his susceptibility to training, it would be a mistake to ignore the data obtainable from other sources. No competent psychologist, however ardent a supporter of the Binet method he might be, would recom¬ mend such a policy. Those who accept the method as all- sufficient are as much in error as those who consider it as no more important than any one of a dozen other ap¬ proaches. Standardized tests have already become and will remain by far the most reliable single method for grad¬ ing intelligence, but the results they furnish will always need to be interpreted in the light of supplementary information regarding the subject’s personal history, including medical record, accidents, play habits, industrial efficiency, social and moral traits, school success, home environment, etc. Without question, however, the improved Binet tests will contribute more than all other data combined to the end of enabling us to forecast a child’s possibilities of future im¬ provement, and this is the information which will aid most in the proper direction of his education.
CHAPTER IV
NATURE OF THE STANFORD REXISION AND EXTENSION
Although the Binet scale quickly demonstrated its value as an instrument for the classification of mentally -retarded and otherwise exceptional children, it had, nevertheless, several imperfections which greatly limited its usefulness. There was a dearth of tests at the higher mental levels, the procedure was so inadequately defined that needless disagreement came about in the interpretation of data, and so many of the tests were misplaced as to make the results of an examination more or less misleading, particu¬ larly in the case of very young subjects and those near the adult level. It was for the purpose of correcting these and certain other faults that the Stanford investigation was planned.1
Sources of data. Our revision is the result of several years of work, and involved the examination of approxi¬ mately 2300 subjects, including 1700 normal children,
1 The writer wishes to acknowledge his very great indebtedness to Miss Grace Lyman, Dr. George Ordahl, Dr. Louise Ellison Ordahl, Miss Neva Galbreath, Mr. Wilford Talbert, Dr. J. Harold Williams, Mr. Herbert E. Knollin, and Miss Irene Cuneo for their cooperation in making the tests on which the Stanford revision is chiefly based. Without their loyal as¬ sistance the investigation could not have been carried through.
Grateful acknowledgment is also made to the many public school teach¬ ers and principals for their generous and invaluable cooperation in furnish¬ ing subjects for the tests, and in supplying, sometimes at considerable cost of labor, the supplementary information which was called for regarding the pupils tested. Their contribution was made in the interest of educa¬ tional science, and without expectation of personal benefits of any kind. Their professional spirit cannot be too highly commended ,
52 THE MEASUREMENT OF INTELLIGENCE
200 defective and superior children, and more than 400 adults.
Tests of 400 of the 1700 normal children had been made by Childs and Terman in 1910-11, and of 300 chil¬ dren by Trost, Waddle, and Terman in 1911-12. For various reasons, however, the results of these tests did not furnish satisfactory data for a thoroughgoing revision of the scale. Accordingly a new investigation was undertaken, somewhat more extensive than the others, and more care¬ fully planned. Its main features may be described as fol¬ lows : —
1. The first step was to assemble as nearly as possible all the results which had been secured for each test of the scale by all the workers of all countries. The result was a large sheet of tabulated data for each individual test, including percentages passing the test at various ages, conditions under which the results were secured, method of procedure, etc. After a comparative study of these data, and in the light of results we had ourselves secured, a provisional arrangement of the tests was prepared for try-out.
2. In addition to the tests of the original Binet scale, 40 additional tests were included for try-out. This, it was expected, would make possible the elimination of some of the least satisfactory tests, and at the same time permit the addition of enough new ones to give at least six tests, instead of five, for each age group.
3. A plan was then devised for securing subjects who should be as nearly as possible representative of the several ages. The method was to select a school in a community of average social status, a school attended by all or prac¬ tically all the children in the district where it was located. In order to get clear pictures of age differences the tests were confined to children who were within two months of a
THE STANFORD REVISION
53
birthday. To avoid accidental selection, all the children within two months of a birthday were tested, in whatever grade enrolled. Tests of foreign-born ‘ children, however, were eliminated in the treatment of results. There remained tests of approximately 1000 children, of whom 905 were between 5 and 14 years of age.
4. The children’s responses were, for the most part, recorded verbatim. This made it possible to re-score the records according to any desired standard, and thus to fit a test more perfectly to the age level assigned it.
5. Much attention was given to securing uniformity of procedure. A half-year was devoted to training the ex¬ aminers, and another half-year to the supervision of the testing. In the further interests of uniformity all the rec¬ ords were scored by one person (the writer).
Method of arriving at a revision. The revision of the scale below the 14-year level was based almost entirely on the tests of the above-mentioned 1,000 unselected children. The guiding principle was to secure an arrangement of the tests and a standard of scoring which would cause the median mental age of the unselected children of each age group to coincide with the median chronological age. That is, a correct scale must cause the average child of 5 years to test exactly at 5, the average child at 6 to test exactly at 6, etc. Or, to express the same fact in terms of intelligence quotient,1 a correct scale must give a median intelligence quotient of unity, or 100 per cent, for unselected children of each age.
If the median mental age resulting at any point from the provisional arrangement of tests was too high or too low, it was only necessary to change the location of certain of the tests, or to change the standard of scoring, until an
1 The intelligence quotient (often designated as I Q) is the ratio of mental age to chronological age. (See pp. 6 5 JJ. and 78 Jf.)
54 THE MEASUREMENT OF INTELLIGENCE
order of arrangement and a standard of passing were found which would throw the median mental age where it be¬ longed. We had already become convinced, for reasons too involved for presentation here, that no satisfactory revision of the Binet scale was possible on any theoretical considera¬ tions as to the percentage of passes which an individual test ought to show in a given year in order to be consid¬ ered standard for that year.
As was to be expected, the first draft of the revision did not prove satisfactory. The scale was still too hard at some points, and too easy at others. In fact, three succes¬ sive revisions were necessary, involving three separate scorings of the data and as many tabulations of the mental ages, before the desired degree of accuracy was secured. As finally revised, the scale gives a median in¬ telligence quotient closely approximating 100 for the unselected children of each age from 4 to 14.
Since our school children who were above 14 years and still in the grades were retarded left-overs, it was neces¬ sary to base the revision above this level on the tests of adults. These included 30 business men and 150 “ migrat¬ ing ” unemployed men tested by Mr. H. E. Knollin, 150 adolescent delinquents tested by Mr. J. Harold Williams, and 50 high-school students tested by the writer.
The extension of the scale in the upper range is such that ordinarily intelligent adults, little educated, test up to what is called the “average adult ” level. Adults whose intelligence is known from other sources to be superior are found to test well up toward the “ superior adult ” level, and this holds whether the subjects in question are well educated or practically unschooled. The almost entirely unschooled business men, in fact, tested fully as well as high-school juniors and seniors.
Figure 1 shows the distribution of mental ages for 62
THE STANFORD REVISION
55
adults, including the 30 business men and the 32 high- school pupils who were over 16 years of age. It will be noted that the middle section of the graph represents the
mental ages ” falling between 15 and 17. This is the range which we have designated as the “ average adult ” level. Those above 17 are called “ superior adults,” those between 13 and 15, “ inferior adults.” Subjects much over 15 years of age who test in the neighborhood of 12 years may ordinarily be considered border-line cases.
The following method was employed for deter¬ mining the validity of a test. The children of each age level were di¬ vided into three groups according to intelli¬ gence quotient, those testing below 90, those between 90 and 109, and those with an in¬ telligence quotient of 110 or above. The per¬ centages of passes on each individual test at or near that age level were then ascertained separately for these three groups. If a test fails to show a decidedly higher propor¬ tion of passes in the superior I Q group than in the inferior I Q group, it cannot be regarded as a satisfactory test of intelligence. On the other hand, a test which satisfies this criterion must be accepted as valid or the entire scale must be rejected. Henceforth it stands or falls with the scale as a whole.
When tried out by this method, some of the tests which have been most criticized showed a high degree of relia-
13 to 13 11 14 to 14 11 15 to 15 11 17 to 17 11 18 to 18 11
1.6 it 17.7* 59.7* 16.2* 4.8*
Fig. 1.
DISTRIBUTION OF MENTAL AGES OF 62 NORMAL ADULTS
56 THE MEASUREMENT OF INTELLIGENCE
bility; certain others which have been considered excellent proved to be so little correlated with intelligence that they had to be discarded.
After making a few necessary eliminations, 90 tests re¬ mained, or 36 more than the number included in the Binet 1911 scale. There are 6 at each age level from 3 to 10, 8 at 12, 6 at 14, 6 at “ average adult,” 6 at “ superior adult,” and 16 alternative tests. The alternative tests, which are distributed among the different groups, are intended to be used only as substitutes when one or more of the regular tests have been rendered, by coaching or otherwise, un¬ desirable.1
Of the 36 new tests, 27 were added and standardized in the various Stanford investigations. Two tests were borrowed from the Healy-Fernald series, one from Kuhl- mann, one was adapted from Bonser, and the remaining five were amplifications or adaptations of some of the earlier Binet tests.
Following is a complete list of the tests of the Stanford revision. Those designated al. are alternative tests. The guide for giving and scoring the tests is presented at length in Part II of this volume.
The Stanford revision and extension Year III. ( 6 tests, 2 months each.)
1. Points to parts of body. (3 of 4.)
Nose; eyes; mouth; hair.
2. Names familiar objects. (3 of 5.)
Key, penny, closed knife, watch, pencil.
3. Pictures, enumeration or better. (At least 3 objects enumer¬ ated in one picture.)
(a) Dutch Home; (6) River Scene; (c) Post-Office.
4. Gives sex.
5. Gives last name.
1 See p. 137 ff. for explanations regarding the calculation of mental age and the use of alternative tests.
THE STANFORD REVISION
57
6. Repeats 6 to 7 syllables. (1 of 3.)
Al. Repeats 3 digits. (1 success in 3 trials. Order correct.)
Year IV. ( 6 tests, 2 months each.)
1. Compares lines. (3 trials, no error.)
2. Discrimination of forms. (Kuhlmann.) (Not over 3 errors.)
3. Counts 4 pennies. (No error.)
4. Copies square. (Pencil. 1 of 3.)
5. Comprehension, 1st degree. (2 of 3.) (Stanford addition.)
“What must you do”: “When you are sleepy?” “Cold?” “Hungry?”
6. Repeats 4 digits. (1 of 3. Order correct.) (Stanford addi¬ tion.)
Al. Repeats 12 to 13 syllables. (1 of 3 absolutely correct, or 2 with 1 error each.)
Year V. (6 tests, 2 months each.)
1. Comparison of weights. (2 of 3.)
3-15; 15-3; 3-15.
2. Colors. (No error.)
Red; yellow; blue; green.
3. ^Esthetic comparison. (No error.)
4. Definitions, use or better. (4 of 6.)
Chair; horse; fork; doll; pencil; table.
5. Patience, or divided rectangle. (2 of 3 trials. 1 minute each.)
6. Three commissions. (No error. Order correct.)
Al. Age.
Year VI. (6 tests, 2 months each.)
1. Right and left. (No error.)
Right hand; left ear; right eye.
2. Mutilated pictures. (3 of 4 correct.)
3. Counts 13 pennies. (1 of 2 trials, without error.)
4. Comprehension, 2d degree. (2 of 3.) “What’s the thing for you to do”:
(a) “If it is raining when you start to school?”
( b ) “If you find that your house is on fire?”
(c) “If you are going some place and miss your car?”
5. Coins. (3 of 4.)
Nickel; penny; quarter; dime.
6. Repeats 16 to 18 syllables. (1 of 3 absolutely correct, or 2 with 1 error each.)
Al. Morning or afternoon.
58 THE MEASUREMENT OF INTELLIGENCE
Year VII. (6 tests, 2 months each.)
1. Fingers. (No error.) Right; left; both.
2. Pictures, description or better. (Over half of performance description:) Dutch Home; River Scene; Post-Office.
3. Repeats 5 digits. (1 of 3. Order correct.)
4. Ties bow-knot. (Model shown. 1 minute.) (Stanford ad¬ dition.)
5. Gives differences. (2 of 3.)
Fly and butterfly; stone and egg; wood and glass.
6. Copies diamond. (Pen. 2 of 3.)
Al. 1. Names days of week. (Order correct. 2 of 3 checks correct.) Al. 2. Repeats 3 digits backwards. (1 of 3.)
Year VIII. (6 tests, 2 months each.)
1. Ball and field. (Inferior plan or better.) (Stanford addi¬ tion.)
2. Counts 20 to 1. (40 seconds. 1 error allowed.)
3. Comprehension, 3d degree. (2 of 3.) “What’s the thing for you to do”:
(a) “When you have broken something which belongs to some one else?”
( b ) “When you are on your way to school and notice that you are in danger of being tardy?”
(c) “If a playmate hits you without meaning to do it?”
4. Gives similarities, two things. (2 of 4.) (Stanford addition.)
Wood and coal; apple and peach; iron and silver; ship and automobile.
5. Definitions superior to use. (2 of 4.)
Balloon; tiger; football; soldier.
6. Vocabulary, 20 words. (Stanford addition. For list of words used, see record booklet.)
Al. 1. First six coins. (No error.)
Al. 2. Dictation. (“See the little boy.” Easily legible. Pen. 1 minute.)
Year IX. ( 6 tests, 2 months each.)
1. Date. (Allow error of 3 days in c, no error in a, b, or d.)
(a) day of week; ( b ) month; (c) day of month; ( d ) year.
2. Weights. (3, 6, 9, 12, 15. Procedure not illustrated. 2 of 3.)
3. Makes change. (2 of 3. No coins, paper, or pencil. 1
10 - 4; 15 - 12; 25 - 4.
THE STANFORD REVISION
59
4. Repeats 4 digits backwards. (1 of 3.) (Stanford addition.)
5. Three words. (2 of 3. Oral. 1 sentence or not over 2 coordi¬ nate clauses.)
Boy, river, ball; work, money, men; desert, rivers, lakes.
6. Rhymes. (3 rhymes for two of three words. 1 minute for each part.)
Day; mill; spring.
Al. 1. Months. (15 seconds and 1 error in naming. 2 checks of 3 correct.)
Al. 2. Stamps, gives total value. (Second trial if individual val¬ ues are known.)
Year X. (6 tests, 2 months each.)
1. Vocabulary, 30 words. (Stanford addition.)
2. Absurdities. (4 of 5. Warn. Spontaneous correction al¬ lowed.) (Four of Binet’s, one Stanford.)
3. Designs. (1 correct, 1 half correct. Expose 10 seconds.)
4. Reading and report. (8 memories. 35 seconds and 2 mis¬ takes in reading.) (Binet’s selection.)
5. Comprehension, 4th degree. ( 2 of 3. Question may be repeated.)
(a) “What ought you to say when some one asks your opinion about a person you don’t know very well?”
(b) “What ought you to do before undertaking (beginning) something very important? ”
(c) “Why should we judge a person more by his actions than by his words?”
6. Names 60 words. (Illustrate with clouds, dog, chair, happy.)
Al. 1. Repeats 6 digits. (1 of 2. Order correct.) (Stanford
addition.)
Al. 2. Repeats 20 to 22 syllables. (1 of 3 correct, or 2 with 1 error each.)
Al. 3. Form board. (Healy-Femald Puzzle A. 3 times in 5 minutes.)
Year XII. ( 8 tests, 3 months each.)
1. Vocabulary, 40 words. (Stanford addition.)
2. Abstract words. (3 of 5.)
Pity; revenge; charity; envy; justice.
3. Ball and field. (Superior plan.) (Stanford addition.)
4. Dissected sentences. (2 of 3. 1 minute each.)
60 THE MEASUREMENT OF INTELLIGENCE
5. Fables. (Score 4; i.e., two correct or the equivalent in half credits.) (Stanford addition.)
Hercules and Wagoner; Maid and Eggs; Fox and Crow; Farmer and Stork; Miller, Son, and Donkey.
6. Repeats 5 digits backwards. (1 of 3.) (Stanford addition.)
7. Pictures, interpretation. (3 of 4. “Explain this picture.”)
Dutch Home; River Scene; Post-Office; Colonial Home.
8. Gives similarities, three things. (3 of 5.) (Stanford addition.)
Snake, cow, sparrow; book, teacher, newspaper; wool, cot¬ ton, leather; knife-blade, penny, piece of wire; rose, potato, tree.
Year XIV. (6 tests, h months each.)
1. Vocabulary, 50 words. (Stanford addition.)
2. Induction test. (Gets rule by 6th folding.) (Stanford addi¬ tion.)
3. President and king. (Power; accession; tenure. 2 of 3.)
4. Problems of fact. (2 of 3.) (Binet’s two and one Stanford addition.)
5. Arithmetical reasoning. (1 minute each. 2 of 3.) (Adapted from Bonser.)
6. Clock. (2 of 3. Error must not exceed 3 or 4 minutes.)
6.22. 8.10. 2.46.
Al. Repeats 7 digits. (1 of 2. Order correct.)
Average Adult.” (6 tests, 5 months each.)
1. Vocabulary, 65 words. (Stanford addition.)
2. Interpretation of fables. (Score 8.) (Stanford addition.)
3. Difference between abstract words. (3 real contrasts out of 4.)
Laziness and idleness; evolution and revolution; poverty and misery; character and reputation.
4. Problem of the enclosed boxes. (3 of 4.) (Stanford addition.)
5. Repeats 6 digits backwards. (1 of 3.) (Stanford addition.)
6. Code, writes “Come quickly.” (2 errors. Omission of dot counts half error. Illustrate with “war” and “spy.”) (From Plealy and Fernald.)
Al. 1. Repeats 28 syllables. (1 of 2 absolutely correct.)
Al. 2. Comprehension of physical relations. (2 of 3.) (Stanford addition.)
Path of cannon ball; weight of fish in water; hitting dis¬ tant mark.
THE STANFORD REVISION
61
“Superior Adult.” (6 tests, 6 months each.)
1. Vocabulary, 75 words. (Stanford addition.)
2. Binet’s paper-cutting test. (Draws, folds, and locates holes.)
3. Repeats 8 digits. (1 of 3. Order correct.) (Stanford addi¬ tion.)
4. Repeats thought of passage heard. (1 of 2.) (Binet’s and Wissler’s selections adapted.)
5. Repeats 7 digits backwards. (1 of 3.) (Stanford addition.)
6. Ingenuity test. (2 of 3. 5 minutes each.) (Stanford addition.)
Summary of changes. A comparison of the above list with either the Binet 1908 or 1911 series will reveal many changes. On the whole, it differs somewhat more from the Binet 1911 scale than from that of 1908. Thus, of the 49 tests below the “ adult ” group in the 1911 scale, 2 are eliminated and 29 are relocated. Of these, 25 are moved downward and 4 upward. The shifts are as follows: —
Down 1 year, 18 Down 2 years, 4 Down 3 years, 2 Down 6 years, 1 Up 1 year, 3 Up 2 years, 1
Of the adult group in Binet’s 1911 series 1 is eliminated, 2 are moved up to “ superior adult,” and 1 is moved up to 14. Accordingly, of Binet’s entire 54 tests, we have elimi¬ nated 3 and relocated 32, leaving only 19 in the positions assigned them by Binet. The 3 eliminated are: repeating 2 digits, resisting suggestion, and “ reversed triangle.”
The revision is really more extensive than the above figures would suggest, since minor changes have been made in the scoring of a great many tests in order to make them fit better the locations assigned them. Throughout the scale the procedure and scoring have been worked over and made more definite with the idea of promoting uni¬ formity. This phase of the revision is perhaps more im-
62 THE MEASUREMENT OF INTELLIGENCE
portant than the mere relocation of tests. Also, the addi¬ tion of numerous tests in the upper ranges of the scale affects very considerably the mental ages above the level of 10 or 11 years.
Effects of the revision on the mental ages secured. The most important effect of the revision is to reduce the mental ages secured in the lower ranges of the scale, and to raise considerably the mental ages above 10 or 11 years. This difference also obtains, though to a somewhat smaller ex¬ tent, between the Stanford revision and those of Goddard and Kuhlmann.
For example, of 104 adult individuals testing by the Stan¬ ford revision between 12 and 14 years, and who were there¬ fore somewhat above the level of feeble-mindedness as that term is usually defined, 50 per cent tested below 12 years by the Goddard revision. That the, dull and border-line adults are so much more readily distinguished from the feeble¬ minded by the Stanford revision than by other Binet series is due as much to the addition of tests in the upper groups as to the relocation of existing tests.
On the other hand, the Stanford revision causes young subjects to test lower than any other version of the Binet scale. At 5 or 6 years the mental ages secured by the Stan¬ ford revision average from 6 to 10 months lower than other revisions yield.
The above differences are more significant than would at first appear. An error of 10 months in the mental age of a 5-year-old is as serious as an error of 20 months in the case of a 10-year-old. Stating the error in terms of the intelli¬ gence quotient makes it more evident. Thus, an error of 10 months in the mental age of a 5-year-old means an error of almost 15 per cent in the intelligence quotient. A scale which tests this much too low would cause the child with a true intelligence quotient of 75 (which ordinarily means
THE STANFORD REVISION
63
feeble-mindedness or border-line intelligence) to test at 90, or only slightly below normal.
Three serious consequences came from the too great ease of the original Binet scale at the lower end, and its too great difficulty at the upper end : —
1. In young subjects the higher grades of mental de¬ ficiency were overlooked, because the scale caused such subjects to test only a little below normal.
2. The proportion of feeble-mindedness among adult subjects was greatly overestimated, because subjects who were really of the 12- or 13-year mental level could only earn a mental age of about 11 years.
3. Confusion resulted in efforts to trace the mental growth of either feeble-minded or normal children. For example, by other versions of the Binet scale an average 5-year-old will show an intelligence quotient probably not far from 110 or 115; at 9, an intelligence quotient of about 100; and at 14, an intelligence quotient of about 85 or 90.
By such a scale the true border-line case would test approximately as follows : —
At age 5, 90 I Q (apparently not far below normal).
At age 9, 75 I Q (border-line).
At age 14, 65 I Q (moron deficiency).
On the other hand, re-tests of children by the Stanford revision have been found to yield intelligence quotients almost identical with those secured from two to four years earlier by the same tests. Those who graded feeble-minded in the first test graded feeble-minded in the second test: the dull remained dull, the average remained average, the superior remained superior, and always in approximately the same degree.1
* See “ Some Problems relating to the Detection of Border-line Cases of Mental Deficiency,” by Lewis M. Terman and H. E. Knollin, in Journal q f Psycho-Asthemes, June, 1916.
64 THE MEASUREMENT OF INTELLIGENCE
It is unnecessary to emphasize further the importance of having an intelligence scale which is equally accurate at all points. Absolute perfection in this respect is not claimed for the Stanford revision, but it is believed to be at least free from the more serious errors of other Binet arrange¬ ments.
CHAPTER V
ANALYSIS OF 1000 INTELLIGENCE QUOTIENTS
An extended account of the 1000 tests on which the Stanford revision is chiefly based has been presented in a separate monograph. This chapter will include only the briefest summary of some of those results of the investiga¬ tion which contribute to the intelligent use of the revi¬ sion.
The distribution of intelligence. The question as to the manner in which intelligence is distributed is one of great practical as well as theoretical importance. One of the most vital questions which can be asked by any nation of any age is the following: “How high is the average level of intelligence among our people, and how frequent are the various grades of ability above and below the average? ” With the development of standardized tests we are ap¬ proaching, for the first time in history, a possible answer to this question.
Most of the earlier Binet studies, however, have thrown little light on the distribution of intelligence because of their failure to avoid the influence of accidental selection in choosing subjects for testing. The method of securing subjects for the Stanford revision makes our results on this point especially interesting.1 It is believed that the sub¬ jects used for this investigation were as nearly representa¬ tive of average American-born children as it is possible to secure.
1 See p. 52 ff. for method used to avoid accidental selection of subjects for the Stanford investigation.
66 THE MEASUREMENT OF INTELLIGENCE
The intelligence quotients for these 1000 unselected chil¬ dren were calculated, and their distribution was plotted for the ages separately. The distribution was found fairly symmetrical at each age from 5 to 14. At 15 the range is on either side of 90 as a median, and at 16 on either side of 80 as a median. That the 15- and 16-year-olds test low is due to the fact that these children are left-over retardates and are below average in intelligence.
The I Q’s were then grouped in ranges of ten. In the middle group were thrown those from 96 to 105; the ascend-
Fiq. 8. DISTRIBUTION OF I Q’S OF 905 UNSELECTED CHILDREN,
5-14 YEARS OF AGE
ing groups including in order the I Q’s from 106 to 115, 116 to 125, etc.; correspondingly with the descending groups. Figure 2 shows the distribution found by this grouping for the 905 children of ages 5 to 14 combined. The subjects above 14 are not included in this curve be¬ cause they are left-overs and not representative of their ages.
The distribution for the ages combined is seen to be re¬ markably symmetrical. The symmetry for the separate ages was hardly less marked, considering that only 80 to 120 children were tested at each age. In fact, the range, including the middle 50 per cent of I Q’s, was found practically constant from 5 to 14 years. The tendency is
INTELLIGENCE QUOTIENTS ANALYZED 67
for the middle 50 per cent to fall (approximately) between 93 and 108.
Three important conclusions are justified by the above facts : • —
1. Since the frequency of the various grades of intelli¬ gence decreases gradually and at no point abruptly on each side of the median, it is evident that there is no defi¬ nite dividing line between normality and feeble-minded¬ ness, or between normality and genius. Psychologically, the mentally defective child does not belong to a distinct type, nor does the genius. There is no line of demarcation between either of these extremes and the so-called “ nor¬ mal ” child. The number of mentally defective individuals in a population will depend upon the standard arbitrarily set up as to what constitutes mental deficiency. Similarly for genius. It is exactly as we should undertake to classify all people into the three groups: abnormally tall, normally tall, and abnormally short.1
2. The common opinion that extreme deviations below the'median are more frequent than extreme deviations above the median seems to have no foundation in fact. Among unselected school children, at least, for every child of any given degree of deficiency there is another child as far above the average I Q as the former is below. We have shown elsewhere the serious consequences of neglect of this fact.2
3. The traditional view that variability in mental traits becomes more marked during adolescence is here contra¬ dicted, as far as intelligence is concerned, for the distribu¬ tion of I Q’s is practically the same at each age from 5 to 14. For example, 6-year-olds differ from one another fully as much as do 14-year-olds.
1 See Chapter VI for discussion of the significance of various I Q’s.
* See p. 12 jf.
68 THE MEASUREMENT OF INTELLIGENCE
The validity of the intelligence quotient. The facts
presented above argue strongly for the validity of the I Q as an expression of a child’s intelligence status. This fol¬ lows necessarily from the similar nature of the distributions at the various ages. The inference is that a child’s I Q, as measured by this scale, remains relatively constant. Re-tests of the same children at intervals of two to five years support the inference. Children of superior intelli¬ gence do not seem to deteriorate as they get older, nor dull children to develop average intelligence. Knowing a child’s I Q, we can predict with a fair degree of accuracy the course of his later development.
The mental age of a subject is meaningless if considered apart from chronological age. It is only the ratio of retarda¬ tion or acceleration to chronological age (that is, the I Q) which has significance.
It follows also that if the I Q is a valid expression of in¬ telligence, as it seems to be, then the Binet-Simon “ age- grade method ” becomes transformed automatically into a “ point-scale method,” if one wants to use it that way. As such it is superior to any other point scale that has been proposed, because it includes a larger number of tests and its points have definite meaning.1
Sex differences. The question as to the relative intelli¬ gence of the sexes is one of perennial interest and great social importance. The ancient hypothesis, the one which dates from the time when only men concerned themselves with scientific hypotheses, took for granted the superiority of the male. With the development of individual psychology, however, it was soon found that as far as the evidence of mental tests can be trusted the average intelligence of women and girls is as high as that of men and boys.
1 For discussion of the supposed advantages of the “point-scale method,” see Yerkes and Bridges: A New Point Scale for Measuring Mental Ability. (Warwick and York, 1915.)
INTELLIGENCE QUOTIENTS ANALYZED 69
If we accept this result we are then confronted with the difficult problem of finding an explanation for the fact that so few of those who have acquired eminence in the various intellectual fields have been women. Two explanations have been proposed: (1) That women become eminent less often than men simply for lack of opportunity and stimulus; and (2) that while the average intelligence of the sexes is the same, extreme variations may be more common in males.
Boy« 1.00 .99 1.01 1.00 .98 1.03 .96 .97 .96 1.00
Girls 1.04 1.08 1.03 1.02 1.02 1.08 1.01 .99 .97 .96
Fig. 3. MEDIAN I Q OF 457 BOYS (UNBROKEN LINE) AND 448 GIRLS (DOTTED LINE) FOR THE AGES 5-14 YEARS
It is pointed out that not only are there more eminent men than eminent women, but that statistics also show a pre¬ ponderance of males in institutions for the mentally de¬ fective. Accordingly it is often said that women are grouped closely about the average, while men show a wider range of distribution.
Many hundreds of articles and books of popular or quasi-scientific nature have been written on one aspect or another of this question of sex difference in intelligence; but all such theoretical discussions taken together are worth
70 THE MEASUREMENT OF INTELLIGENCE
less than the results of one good experiment. Let us see what our 1000 I Q’s have to offer toward a solution of the problem.
1. When the I Q’s of the boys and girls were treated separately there was found a small but fairly constant superiority of the girls up to the age of 13 years. At 14, however, the curve for the girls dropped below that for boys. This is shown in Figure 3.
The supplementary data, including the teachers’ esti¬ mates of intelligence on a scale of five, the teachers’ judg¬ ments in regard to the quality of the school work, and rec¬ ords showing the age-grade distribution of the sexes, were all sifted for evidence as to the genuineness of the apparent superiority of the girls age for age. The results of all these lines of inquiry support the tests in suggesting that the superiority of the girls is probably real even up to and in¬ cluding age 14, the apparent superiority of the boys at this age being fully accounted for by the more frequent elimination of 14-year-old girls from the grades by promo¬ tion to the high school.1
2. However, the superiority of girls over boys is so slight (amounting at most ages to only 2 to 3 points in terms of I Q) that for practical purposes it would seem negligi¬ ble. This offers no support to the opinion expressed by Yerkes and Bridges that “ at certain ages serious injus¬ tice will be done individuals by evaluating their scores in the light of norms which do not take account of sex differences.”
3. Apart from the small superiority of girls, the dis¬ tribution of intelligence in the two sexes is not different. The supposed wider variation of boys is not found. Girls do not group themselves about the median more closely
1 It will be remembered that this series of tests did not follow up and test those who had been promoted to high school.
INTELLIGENCE QUOTIENTS ANALYZED 71
than do boys. The range of I Q including the middle fifty per cent is approximately the same for the two sexes.1
4. When the results for the individual tests were ex¬ amined, it was found that not many showed very extreme differences as to the per cent of boys and girls passing. In a few cases, however, the difference was rather marked.
The boys were decidedly better in arithmetical reason¬ ing, giving differences between a president and a king, solv¬ ing the form board, making change, reversing hands of clock, finding similarities, and solving the “ induction test.” The girls were superior in drawing designs from memory, aesthetic comparison, comparing objects from memory, an¬ swering the “comprehension questions,” repeating digits and sentences, tying a bow-knot, and finding rhymes.
Accordingly, our data, which for the most part agree with the results of others, justify the conclusion that the intelligence of girls, at least up to 14 years, does not differ materially from that of boys either as regards the average level or the range of distribution. It may still be argued that the mental development of boys beyond the age of 14 years lasts longer and extends farther than in the case of girls, but as a matter of fact this opinion receives lit¬ tle support from such tests as have been made on men and women college students.
The fact that so few women have attained eminence may be due to wholly extraneous factors, the most impor¬ tant of which are the following: (1) The occupations in which it is possible to achieve eminence are for the most part only now beginning to open their doors to women. Women’s career has been largely that of home-making,
1 For an extensive summary of other data on the variability of the sexes see the article by Leta S. Hollingworth, in The American Journal of Sociology (January, 1914), pp. 510-30. It is shown that the findings of others support the conclusions set forth above.
72 THE MEASUREMENT OF INTELLIGENCE
an occupation in which eminence, in the strict sense of the word, is impossible. (2) Even of the small number of women who embark upon a professional career, a majority marry and thereafter devote a fairly large proportion of their energy to bearing and rearing children. (3) Both the training given to girls and the general atmosphere in which they grow up are unfavorable to the inculcation of the pro¬ fessional point of view, and as a result women are not spurred on by deep-seated motives to constant and strenuous in¬ tellectual endeavor as men are. (4) It is also possible that the emotional traits of women are such as to favor the development of the sentiments at the expense of innate intellectual endowment.
Intelligence of the different social classes. Of the 1000 children, 492 were classified by their teachers according to social class into the following five groups: very inferior, in¬ ferior, average, superior, and very superior. A comparative study was then made of the distribution of I Q’s for these different groups.1
The data may be summarized as follows : —
1. The median I Q for children of the superior social class is about 7 points above, and that of the inferior social class about 7 points below, the median I Q of the average social group. This means that by the age of 14 inferior class children are about one year below, and superior class children one year above, the median mental age for all classes taken together.
2. That the children of the superior social classes make a better showing in the tests is probably due, for the most part, to a su¬ periority in original endowment. This conclusion is supported by five supplementary lines of evidence: (a) the teachers’ rankings of the children according to intelligence; (6) the age-grade pro¬ gress of the children; (c) the quality of the school work; ( d ) the comparison of older and younger children as regards the influence
1 The results of this comparison have been set forth in detail in the monograph of source material and some of the conclusions have been set forth on p. 115 jj. of the present volume.
INTELLIGENCE QUOTIENTS ANALYZED 73
of social environment; and (e) the study of individual cases of bright and dull children in the same family.
3. In order to facilitate comparison, it is advisable to express the intelligence of children of all social classes in terms of the same objective scale of intelligence. This scale should be based on the median for all classes taken together.
4. As regards their responses to individual tests, our children of a given social class were not distinguishable from children of the same intelligence in any other social class.
The relation of the I Q to the quality of the child’s school work. The school work of 504 children was graded by the teachers on a scale of five grades: very inferior, inferior, average, superior, and very superior. When this grouping was compared with that made on the basis of I Q, fairly close agreement was found. However, in about one case out of ten there was rather serious disagreement; a child, for example, would be rated as doing average school work when his I Q would place him in the very inferior intelligence group.
When the data were searched for explanations of such disagreements it was found that most of them were plainly due to the failure of teachers to take into account the age of the child when grading the quality of his school work.1 When allowance was made for this tendency there were no disagreements which justified any serious suspicion as to the accuracy of the intelligence scale. Minor disagree¬ ments may, of course, be disregarded, since the quality of school work depends in part on other factors than intelli¬ gence, such as industry, health, regularity of attendance, quality of instruction, etc.
The relation between I Q and grade progress. This comparison, which was made for the entire 1000 children, showed a fairly high correlation, but also some astonishing disagreements. Nine-year intelligence was found all the
1 See p. 24 jf.
74 THE MEASUREMENT OF INTELLIGENCE
way from grade 1 to grade 7, inclusive; 10-year intelligence all the way from grade 2 to grade 7; and 12-year intelligence all the way from grade 3 to grade 8. Plainly the school’s efforts at grading fail to give homogeneous groups of chil¬ dren as regards mental ability. On the whole, the grade location of the children did not fit their mental ages much better than it did their chronological ages.
When the data were examined, it was found that prac¬ tically every child whose grade failed to correspond fairly closely with his mental age was either exceptionally bright or exceptionally dull. Those who tested between 96 and 105 I Q were never seriously misplaced in school. The very dull children, however, were usually located from one to three grades above where they belonged by mental age, and the duller the child the more serious, as a rule, was the misplacement. On the other hand, the very bright children were nearly always located from one to three grades below where they belonged by mental age, and the brighter the child the more serious the school’s mistake. The child of 10-year mental age in the second grade, for example, is almost certain to be about 7 or 8 years old; the child of 10- year intelligence in the sixth grade is almost certain to be 13 to 15 years of age.
All this is due to one fact, and one alone: the school tends to 'promote children hy age rather than ability. The bright children are held back, while the dull children are promoted beyond their mental ability. The retardation problem is exactly the reverse of what we have thought it to be. It is the bright children who are retarded, and the dull chil¬ dren who are accelerated.
The remedy is to be sought in differentiated courses (special classes) for both kinds of mentally exceptional children. Just as many special classes are needed for su- nerior children as for the inferior. The social consequences
INTELLIGENCE QUOTIENTS ANALYZED
75
of suitable educational advantages for children of superior ability would no doubt greatly exceed anything that could possibly result from the special instruction of dullards and border-line cases.1
Special study of the I Q’s between 70 and 79 revealed the fact that a child of this grade of intelligence never does satisfactory work in the grade where he belongs by chrono¬ logical age. By the time he has attended school four or five years, such a child is usually found doing “ very inferior ” to “ average ” work in a grade from two to four years below his age.
On the other hand, the child with an I Q of 120 or above is almost never found below the grade for his chronological age, and occasionally he is one or two grades above. Wher¬ ever located, his work is always “ superior ” or “ very superior,” and the evidence suggests strongly that it would probably remain so even if extra promotions were granted.
Correlation between I Q and the teachers’ estimates of the children’s intelligence. By the Pearson formula the correlation found between the I Q’s and the teachers’ rank¬ ings on a scale of five was .48. This is about what others have found, and is both high enough and low enough to be significant. That it is moderately high in so far cor¬ roborates the tests. That it is not higher means that either the teachers or the tests have made a good many mis¬ takes.
When the data were searched for evidence on this point, it was found, as we have shown in Chapter II, that the fault was plainly on the part of the teachers. The serious mis¬ takes were nearly all made with children who were either over age or under age for their grade, mostly the former.
: See Chapter VI for further discussion of the school progress possible to children of various I Q’s.
76 THE MEASUREMENT OF INTELLIGENCE
In estimating children’s intelligence* just as in grading their school success, the teachers often failed to take account of the age factor. For example, the child whose mental age was, say, two years below normal, and who was enrolled in a class with children about two years younger than himself, was often graded “ average ” in intelligence.
The tendency of teachers is to estimate a child’s intelli¬ gence according to the quality of his school work in the grade where he happens to be located. This results in over¬ estimating the intelligence of older, retarded children, and underestimating the intelligence of the younger, ad¬ vanced children. The disagreements between the tests and the teachers’ estimates are thus found, when analyzed, to confirm the validity of the test method rather than to bring it under suspicion.
The validity of the individual tests. The validity of each test was checked up by measuring it against the scale as a whole in the manner described on p. 55. For example, if 10-year-old children having 11-year intelligence succeed with a given test decidedly better than 10-year-old chil¬ dren who have 9-year intelligence, then either this test must be accepted as valid or the scale as a whole must be rejected. Since we know, however, that the scale as a whole has at least a reasonably high degree of reliability, this method becomes a sure and ready means of judging the worth of a test.
When the tests were tried out in this way it was found that some of those which have been most criticized have in real¬ ity a high correlation with intelligence. Among these are naming the days of the week, giving the value of stamps, counting thirteen pennies, giving differences between presi¬ dent and king, finding rhymes, giving age, distinguishing right and left, and interpretation of pictures. Others hav¬ ing a high reliability are the vocabulary tests, arithmetical
INTELLIGENCE QUOTIENTS ANALYZED
77
reasoning, giving differences, copying a diamond, giving date, repeating digits in reverse order, interpretation of fables, the dissected sentence test, naming sixty words, finding omissions in pictures, and recognizing absurdities.
Among the somewhat less satisfactory tests are the fol¬ lowing: repeating digits (direct order), naming coins, dis¬ tinguishing forenoon and afternoon, defining in terms of use, drawing designs from memory, and aesthetic compari¬ son. Binet’s “line suggestion ” test correlated so little with intelligence that it had to be thrown out. The same was also true of two of the new tests which we had added to the series for try-out.
Tests showing a medium correlation with the scale as a whole include arranging weights, executing three com¬ missions, naming colors, giving number of fingers, describ¬ ing pictures, naming the months, making change, giving superior definitions, finding similarities, reading for mem¬ ories, reversing hands of clock, defining abstract words, problems of fact, bow-knot, induction test, and compre¬ hension questions.
A test which makes a good showing on this criterion of agreement with the scale as a whole becomes immune to theoretical criticisms. Whatever it appears to be from mere inspection, it is a real measure of intelligence. Hence¬ forth it stands or falls with the scale as a whole.
The reader will understand, of course, that no single test used alone will determine accurately the general level of intelligence. A great many tests are required; and for two reasons: (1) because intelligence has many aspects; and (2) in order to overcome the accidental influences of training or environment. If many tests are used no one of them need show more than a moderately high correlation with the scale as a whole. As stated by Binet, “ Let the tests be rough, if there are only enough of them.”
CHAPTER VI
THE SIGNIFICANCE OF VARIOUS INTELLIGENCE QUOTIENTS
Frequency of different degrees of intelligence. Before we can interpret the results of an examination it is neces¬ sary to know how frequently an I Q of the size found occurs among unselected children. Our tests of 1000 unselected children enable us to answer this question with some degree of definiteness. A study of these 1000 I Q’s shows the fol¬ lowing significant facts: —
The lowest 1 % go to 70 or below, the highest 1 % reach 130 or above
|
44 |
(4 |
2 % |
it it ti |
44 |
44 |
44 |
2 |
% |
44 |
128 “ |
44 |
|
ft |
44 |
3 % |
it M if |
44 |
44 |
44 |
3 |
% |
44 |
125 “ |
44 |
|
II |
44 |
5 % |
if if rf g “ |
44 |
44 |
44 |
5 |
% |
44 |
122 “ |
44 |
|
II |
44 |
10 % |
“ “ 85 “ |
44 |
44 |
44 |
10 |
% |
44 |
116 “ |
44 |
|
II |
44 |
15 % |
“ “ 88 “ |
44 |
44 |
44 |
15 |
% |
44 |
113 “ |
44 |
|
44 |
44 |
20 % |
“ “ 91 “ |
44 |
44 |
44 |
20 |
% |
44 |
110 “ |
44 |
|
44 |
44 |
25 % |
“ “ 92 “ |
44 |
44 |
44 |
25 |
% |
44 |
108 " |
44 |
|
44 |
44 |
S3M% |
“ “ 95 “ |
44 |
44 |
44 |
33M% |
44 |
106 “ |
44 |
Or, to put some of the above facts in another form : —
The child reaching 110 is equaled or excelled by 20 out of 100
“ “ “ (about) 115 “ “ “ “ “ 10 “ “ “
** « « « 125 M “ « » g « << <<
<< M « << 130 M ** ** « *< | U 44 («
Conversely, we may say regarding the subnormals that : — The child testing at (about) 90 is equaled or excelled by 80 out of 100
|
44 |
44 |
44 |
44 |
“ 85 “ |
44 |
44 |
44 |
“ 90 |
|
44 |
44 |
44 |
44 |
“ 75 “ |
44 |
44 |
44 |
“ 97 |
|
<4 |
44 |
44 |
44 |
“ 70 “ |
44 |
44 |
44 |
“ 99 |
44 44 44
INTELLIGENCE QUOTIENT SIGNIFICANCE 79
Classification of intelligence quotients. What do the above I Q’s imply in such terms as feeble-mindedness, border-line intelligence, dullness, normality, superior in¬ telligence, genius, etc.? When we use these terms two facts must be borne in mind: (1) That the boundary lines be¬ tween such groups are absolutely arbitrary, a matter of definition only; and (2) that the individuals comprising one of the groups do not make up a homogeneous type.
Nevertheless, since terms like the above are convenient and will probably continue to be used, it is desirable to give them as much definiteness as possible. On the basis of the tests we have made, including many cases of all grades of intelligence, the following suggestions are offered for the classification of intelligence quotients : —
1 Q Classification
Above 140 .... “Near” genius or genius.
120-140 .... Very superior intelligence.
110-120 .... Superior intelligence.
90-110 .... Normal, or average, intelligence.
80- 90 .... Dullness, rarely classifiable as feeble-mindedness.
70- 80 .... Border-line deficiency, sometimes classifiable as dull¬ ness, often as feeble-mindedness.
Below 70 .... Definite feeble-mindedness.
Of the feeble-minded, those between 50 and 70 I Q in¬ clude most of the morons (high, middle, and low), those between 20 or 25 and 50 are ordinarily to be classed as imbeciles, and those below 20 or 25 as idiots. According to this classification the adult idiot would range up to about 3-year intelligence as the limit, the adult imbecile would have a mental level between 3 and 7 years, and the adult moron would range from about 7-year to 11-year intelligence.
It should be added, however, that the classification of I Q’s for the various sub-grades of feeble-mindedness is not very secure, for the reason that the exact curves of mental growth have not been worked out for such grades.
80 THE MEASUREMENT OF INTELLIGENCE
As far as the public schools are concerned this does not greatly matter, as they never enroll idiots and very rarely even the high-grade imbecile. School defectives are prac¬ tically all of the moron and border-line grades, and these it is important teachers should be able to recognize. The following discussions and illustrative cases will perhaps give a fairly definite idea of the significance of various grades of intelligence.1
Feeble-mindedness (rarely above 75 I Q.) There are innumerable grades of mental deficiency ranging from somewhat below average intelligence to profound idiocy. In the literal sense every individual below the average is more or less mentally weak or feeble. Only a relatively small proportion of these, however, are technically known as feeble-minded. It is therefore necessary to set forth the criterion as to what constitutes feeble-mindedness in the commonly accepted sense of that word.
The definition in most general use is the one framed by the Royal College of Physicians and Surgeons of London, and adopted by the English Royal Commission on Mental Deficiency. It is substantially as follows: —
A feeble-minded 'person is one who is incapable, because of mental defect existing from birth or from an early age,
(a) of competing on equal terms with his normal fellows; or
(b) of managing himself or his affairs with ordinary prudence.
Two things are to be noted in regard to this definition:
In the first place, it is stated in terms of social and in¬ dustrial efficiency. Such efficiency, however, depends not merely on the degree of intelligence, but also on emotional, moral, physical, and social traits as well. This explains why some individuals with I Q somewhat below 75 can
1 The clinical descriptions to be given are not complete and are designed merely to aid the examiner in understanding the significance of intelligence quotients found.
INTELLIGENCE QUOTIENT SIGNIFICANCE 81
hardly be classed as feeble-minded in the ordinary sense of the term, while others with I Q a little above 75 could hardly be classified in any other group.
In the second place, the criterion set up by the definition is not very definite because of the vague meaning of the expression “ ordinary prudence.” Even the expression “ competing on equal terms ” cannot be taken literally, else it would include also those who are merely dull. It is the second part of the definition that more nearly ex¬ presses the popular criterion, for as long as an individual manages his affairs in such a way as to be self-supporting, and in such a way as to avoid becoming a nuisance or burden to his fellowmen, he escapes the institutions for defectives and may pass for normal.
The most serious defect of the definition comes from the lax interpretation of the term “ ordinary prudence,” etc. The popular standard is so low that hundreds of thou¬ sands of high-grade defectives escape identification as such. Moreover, there are many grades of severity in social and industrial competition. For example, most of the members of such families as the Jukes, the Nams, the Hill Folk, and the Kallikaks are able to pass as normal in their own crude environment, but when compelled to compete with average American stock their deficiency becomes evident. It is therefore necessary to supplement the social criterion with a more strictly psychological one.
For this purpose there is nothing else as significant as the I Q. All who test below 70 I Q by the Stanford revision of the Binet-Simon scale should be considered feeble-minded, and it is an open question whether it would not be justifiable to consider 75 I Q as the lower limit of “ normal ” intelli¬ gence. Certainly a large proportion falling between 70 and 75 can hardly be classed as other than feeble-minded, even according to the social criterion.
82 THE MEASUREMENT OF INTELLIGENCE
Examples of feeble-minded school children F. C. Boy, age 8-6; mental age J/.-2; I Q approximately 50. From a very superior home. Has had the best medical care and other attention. Attended a private kindergarten until rejected because he required so much of the teacher’s time and appeared uneducable. Will probably develop to about the 6- or 7-year mental level. High grade imbecile. Has since been committed to a state insti¬ tution. Cases as low as F. C. very rarely get into the public schools.
R. W. Boy, age 13-10; mental age 7-6; I Q approximately 55. Home excellent. Is pubescent. Because of age and maturity has
Fia. 4. DIAMOND DRAWN BY R. W., AGE 13-10; MENTAL AGE 7-6
been promoted to the third grade, though he can hardly do the work of the second. Has attended school more than six years. Will probably never develop much if any beyond 8 years, and will never be self-supporting. Low-grade moron.
M. S. Girl, age 7-6 ; mental age 1/.-6; I Q 60. Father a gardener, home conditions and medical attention fair. Has twice attempted first grade, but without learning to read more than a few words. In each case teacher requested parents to withdraw her. “Takes” things. Is considered “foolish” by the other children. Will prob¬ ably never develop beyond a mental level of 8 years.
R. M. Boy, age 15; mental age 9; I Q 60. Decidedly superior home environment and care. After attending school eight years
INTELLIGENCE QUOTIENT SIGNIFICANCE 83
is in fifth grade, though he cannot do the work of the fourth grade. Parents unable to teach him to respect property. Boys torment him and make his life miserable. At middle-moron level and has probably about reached the limit of his development. Has since been committed to a state institution.
Fig. 5. WHITING FROM DICTATION. R. M., AGE 15; MENTAL AGE »
S. M. Girl, age 19-2; mental age 10; I Q approximately 65 ( not counting age beyond 16). From very superior family. Has attended public and private schools twelve years and has been promoted to seventh grade, where she cannot do the work. Appears docile and childlike, but is subject to spells of disobedience and stubbornness. Did not walk until 4 years old. Plays with young children. Sus¬ ceptible to attention from men and has to be constantly guarded. Writing excellent, knows the number combinations, but missed all the absurdities and has the vocabulary of an average 10-year-old. The type from which prostitutes often come.
R. II. Boy, age H; mental age 8~h; 1 Q 65. Father Irish, mother Spanish. Family comfortable and home care average. Has at¬ tended school eight years and is unable to do fourth-grade work satisfactorily. Health excellent and attendance regular. Reads in fourth reader without expression and with little comprehension of what is read. Fair skill in number combinations. Writing and drawing very poor. Cannot use a ruler. Has no conception of an inch.
R. H. is described as high-tempered, irritable, lacking in physi¬ cal activity, clumsy, and unsteady. Plays little. Just “stands around.” Indifferent to praise or blame, has little sense of duty, plays underhand tricks. Is slow, absent-minded, easily confused, in thought, never shows appreciation or interest. So apathetic that he does not hear commands. Voice droning. Speech poor in colloquial expressions.
84 THE MEASUREMENT OF INTELLIGENCE
Three years later, at age of 17, was in a special class attempting sixth-grade work. Reported as doing “absolutely nothing” in that grade. Still sullen, indifferent, and slow in grasping directions, and lacking in play interests. “No apperception of anything, but has mastered such mechanical things as reading (calling the words) and the fundamentals in arithmetic.”
In school work, moral traits, and out-of-school behavior R. H. shows himself to be a typical case of moron deficiency.
7. M. Girl, age 1^-2; mental age 9; I Q approximately 65. Father a laborer. Does unsatisfactory work in fourth grade. Plays with
little girls. A menace to the morals of the school because of her sex in¬ terests and lack of self-restraint. Rather good-looking if one does not hunt for appearances of intel¬ ligence. Mental reactions intoler¬ ably slow. Will develop but little further and will always pass as feeble-minded in any but the very lowest social environment.
G. V. Boy, age 10; mental age Flo. e. BALL AND FIELD TEST. 6-4; 1 Q 65. Father Spanish, I. M., AGE 14-2; MENTAL AGE 9 mother English. Family poor but
fairly respectable. Brothers and sisters all retarded. In high first grade. Work all very poor except writing, drawing, and hand work, in all of which he excels. Is quiet and inactive, lacks self-confidence, and plays little. Mentally slow, inert, “thick,” and inattentive. Health fair.
Three years later G. V. was in the low third grade and still doing extremely poor work in everything except manual training, drawing, and writing. Is not likely ever to go beyond the fourth or fifth grade however long he remains in school.
V. J. Girl, age 11-6; mental age 8; I Q 70. Has been tested three times in the last five years, always with approximately the same result in terms of I Q. Home fair to inferior. Has been in a special class two years and in school altogether nearly six years. Is barely able to do third-grade work. Her feeble-mindedness is
INTELLIGENCE QUOTIENT SIGNIFICANCE 85
recognized by teachers and by other pupils. Belongs at about middle-moron to high-moron level.
A. IV. Boy, age 9 —1^; mental age 7; I Q 75. A year and a half ago he tested at 6—2. From superior family, brothers of very superior intelligence. In school three years and has made about a grade and a half. Has higher I Q than V. J. described above, but his deficiency is fully as evident. Is gener¬ ally recognized as mentally defective. Slyly abstracted one of the pennies used in the test and slipped it in- Fig. 7. DIAMOND DRAWN BY A. W. to his pocket. Has caused
much trouble at school by puncturing bicycle tires. High-grade moron.
A. C. Boy, age 12; mental age 8-5; I Q 70. From Portuguese family of ten children. Has a feeble-minded brother. Parents in comfortable circumstances and respectable. A. C. has attended school regularly since he was 6 years old. Trying unsuccessfully to do the work of the fourth grade. Reads poorly in the third reader. Hesitates, repeats, miscalls words, and never gets the thought. Writes about like a first-grade pupil. Cannot solve such simple problems as “ How many marbles can you buy for ten cents if one marble costs five cents?” even when he has marbles and money in his hands. Described by teacher as “mentally slow and inert, in¬ attentive, easily distracted, memory poor, ideas vague and often absurd, does not appreciate stories, slow at comprehending com¬ mands.” Is also described as “unruly, boisterous, disobedient, stubborn, and lacking sense of propriety. Tattles.”
Three years later, at age of 15, was in a special class and was little if any improved. He had, however, learned the mechanics of reading and had mastered the number combinations. Deficiencies described as “of wide range.” Conduct, however, had improved. Was “working hard to get on.”
A. C. must be considered definitely feeble-minded.
II. S. Boy, age 11; mental age 8-3; I Q approximately 75. At 8 years tested at 6. Parents highly educated, father a scholar.
86 THE MEASUREMENT OF INTELLIGENCE
Brother and sister of very superior intelligence. Started to school at 7, but was withdrawn because of lack of progress. Started again at 8 and is now doing poor work in the second grade. Weakly and nervous. Painfully aware of his inability to learn. During the test keeps saying, “I tried anyway,” “It’s all I can do if I try my best, ain’t it?” etc. Regarded defective by other children. Will prob¬ ably never be able to do work beyond the fourth or fifth grade and is not likely to develop above the 11-year level, if as high.
Fia. 8. DRAWING DESIGNS FROM MEMORY. H. S., AGE 11; MENTAL AGE 8-3
I. S. Boy, age 9-6; mental age 7; I Q 75. German parentage. Started to school at 6. Now in low second grade and unable to do the work. Health good. Inattentive, mentally slow and inert, easily distracted, speech is monotone. Equally poor in reading, writing, and numbers. I. S. is described as quiet, sullen, indifferent, lazy, and stubborn. Plays little.
Three years later had advanced from low second to low fourth grade, but was as poor as ever in his school work. “Miscalls the simplest words.” Moral traits unsatisfactory. May reach sixth or seventh grade if he remains in school long enough.
I. S. learned to walk at 2 years and to talk at 3.
The above are cases of such marked deficiency that there could be no disagreement among competent judges in classifying them in the group of “ feeble-minded.” All are definitely institutional cases. It is a matter of record, however, that one of the cases, H. S., was diagnosed by a physician (without test) as “ backward but not a defec¬ tive,” and with the added encouragement that “ the back"
INTELLIGENCE QUOTIENT SIGNIFICANCE 87
wardness will be outgrown.” Of course ihe reverse is the case; the deficiency is becoming more and more apparent as the boy approaches the age where more is expected of him.
In at least three of the above cases (S. M., I. S., and I. M.) the teachers had not identified the backwardness as feeble-mindedness. Not far from 2 children out of 100, or 20 out of 1000, in the average public school are as defec¬ tive as some of those just described. Teachers get so ac¬ customed to seeing a few of them in every group of 200 or 300 pupils that they are likely to regard them as merely dull, — “ dreadfully dull,” of course, — but not defective.
Children like these, for their own good and that of other pupils, should be kept out of the regular classes. They will rarely be equal to the work of the fifth grade, however long they attend school. They will make a little progress in a well-managed special class, but with the approach of adoles¬ cence, at latest, the State should take them into custodial care for its own protection.
Border-line cases (usually between 70 and 80 I Q).
The border-line cases are those which fall near the bound¬ ary between that grade of mental deficiency which will be generally recognized as such and the higher group usually classed as normal but dull. They are the doubtful cases, the ones we are always trying (rarely with success) to restore to normality.
It must be emphasized, however, that this doubtful group is not marked off by definite I Q limits. Some chil¬ dren with I Q as high as 75 or even 80 will have to be classified as feeble-minded; some as low as 70 I Q may be so well endowed in other mental traits that they may manage as adults to get along fairly well in a simple en¬ vironment. The ability to compete with one’s fellows in the social and industrial world does not depend upon in-
88 THE MEASUREMENT OF INTELLIGENCE
telligence alone. Such factors as moral traits, industry, environment to be encountered, personal appearance, and influential relatives are also involved. Two children classi¬ fied above as feeble-minded had an I Q as high as 75. In these cases the emotional, moral, or physical qualities were so defective as to render a normal social life out of the ques¬ tion. This is occasionally true even with an I Q as high as 80. Some of the border-line cases, with even less intelli¬ gence, may be so well endowed in other mental traits that they are capable of becoming dependable unskilled laborers, and of supporting a family after a fashion.
Examples of border-line deficiency S. F. Girl, age 17; mental age 11-6; I Q approximately 72 ( dis¬ regarding age above 16 years). Father intelligent; mother probably
high-grade defective. Lives in a good home with aunt, who is a woman of good sense and skillful in her manage¬ ment of the girl. S. F. has attended excellent schools for eleven years and has recently been promoted to the seventh grade. The teacher admits, however, that she cannot do the work of that grade, but says, “I have n’t the heart to let her fail in the sixth grade for the third time.” She studies very hard and says she wants to be¬ come a teacher! At the time the test
Fiq. 9. BALL AND FIELD TEST. was made she was actually studying S. F„ AGE 17; MENTAL AGE n-6 her books from two to three hours
daily at home. The aunt, who is very intelligent, had never thought of this girl as feeble-minded, and had suffered much concern and humiliation because of her inability to teach her to conduct herself properly toward men and not to appropriate other people’s property.
S. F. is ordinarily docile, but is subject to fits of anger and ob¬ stinacy. She finally determined to leave her home, threatening to take up with a man unless allowed to work elsewhere. Since then she has been tried out in several families, but after a little while in
INTELLIGENCE QUOTIENT SIGNIFICANCE 89
a place she flies into a rage and leaves. She is a fairly capable houseworker when she tries.
This young woman is feeble-minded and should be classed as such. She is listed here with the border-line cases simply for the reason that she belongs to a group whose mental deficiency is almost never recognized without the aid of a psychological test. Probably no physician could be found who would diagnose the case, on the basis of a medical examination alone, as one of feeble¬ mindedness.
F. H. Boy, age 16-6; mental age 11-5; 1 Q approximately 72 ( disregarding aye above 16 years). Tested for three successive years without change of more than four points in I Q. Father a laborer, dull, subject to fits of rage, and beats the boy. Mother not far from border-line. F. H. has always had the best of school advantages and has been promoted to the seventh grade. Is really about equal to fifth-grade work. Fairly rapid and accurate in number com¬ binations, but cannot solve arithmetical problems which require any reasoning. Reads with reasonable fluency, but with little un¬ derstanding. Appears exceedingly good-natured, but was once suspended from school for hurling bricks at a fellow pupil. Played a “joke” on another pupil by fastening a dangerous, sharp-pointed, steel paper-file in the pupil’s seat for him to sit down on. He is cruel, stubborn, and plays truant, but is fairly industrious when he gets a job as errand or delivery boy. Discharged once for taking money.
F. H. is generally called “ queer,” but is not ordinarily thought of as feeble-minded. His deficiency is real, however, and it is alto¬ gether doubtful whether he will be able to make a living and to keep out of trouble, though he is now (at age 20) employed as mes¬ senger boy for the Western Union at $30 per month. This is con¬ siderably less than pick-and-shovel men get in the community where he lives. Delinquents and criminals often belong to this level of intelligence.
W. C. Boy, age 16-8; mental age 12; I Q 75 ( disregarding age above 16 years). Father a college professor. All the other children in the family of unusually superior intelligence. When tested (four years ago) was trying to do seventh-grade work, but with little success. Wanted to leave school and learn farming, but father insisted on his getting the usual grammar-school and high-school
90 THE MEASUREMENT OF INTELLIGENCE
education. Made $25 one summer by raising vegetables on a vacant lot. In the four years since the test was made he has managed to get into high school. Teachers say that in spite of his best efforts he learns next to nothing, and they regard him as hopelessly dull. Is docile, lacks all aggressiveness, looks stupid, and has head circum¬ ference an inch below normal.
Here is a most pitiful case of the overstimulated backward child in a superior family. Instead of nagging at the boy and urging him on to attempt things which are impossible to his inferior intel¬ ligence, his parents should take him out of school and put him at some kind of work which he could do. If the boy had been the son of a common laborer he would probably have left school early and have become a dependable and contented laborer. In a very simple environment he would probably not be considered defective.
C. P. Boy, age 10-2; mental age 7-11; I Q 78. Portuguese boy, son of a skilled laborer. One of eleven children, most of whom have about this same grade of intelligence. Has attended school regu¬ larly for four years. Is in the third grade, but cannot do the work. Except for extreme stubbornness his social development is fairly normal. Capable in plays and games, but is regarded as impossible in his school work. Like his brother, M. P., the next case to be described, he will doubtless become a fairly reliable laborer at un- skiil ?d work and will not be regarded, in his rather simple environ¬ ment, as a defective. From the psychological point of view, how¬ ever, his deficiency is real. He will probably never develop beyond the 11- or 12-year level or be able to do satisfactory school work beyond the fifth or sixth grade.
Fig. 10. WRITING FROM DICTATION.
MENTAL AGE 7-11
C. P., AGE 10-2;
M. P. Boy, age H; mental age 10-8; I Q 77. Has been tested four successive years, I Q being always between 75 and 80. Brother to C. P. above. In school nearly eight years and has been promoted to the fifth grade. At 16 was doing poor work in the sixth grade. Good school advantages, as the father has tried conscientiously to
INTELLIGENCE QUOTIENT SIGNIFICANCE 91
give his children “a good education.” Perfectly normal in appear¬ ance and in play activities and is liked by other children. Seems to be thoroughly dependable both in school and in his outside work. Will probably become an excellent laborer and will pass as perfectly normal, notwithstanding a grade of intelligence which will not develop above 11 or 12 years.
What shall we say of cases like the last two which test at high-grade moronity or at border-line, but are well enough endowed in moral and personal traits to pass as normal in an uncomplicated social en¬ vironment? According to the classical definition of feeble¬ mindedness such individuals cannot be considered defectives.
Hardly any one would think of them as institutional cases.
Among laboring men and ser¬ vant girls there are thousands like them. They are the world’s “ hewers of wood and drawers of water.” And yet, as far as intelligence is concerned, the tests have told the truth. These boys are uneducable be¬ yond the merest rudiments of training. No amount of school instruction will ever make them intelligent voters or capable citizens in the true sense of the word. Judged psychologically they cannot be considered normal.
It is interesting to note that M. P. and C. P. represent the level of intelligence which is very, very common among Spanish-Indian and Mexican families of the Southwest and also among negroes. Their dullness seems to be racial, or at least inherent in the family stocks from which they come. The fact that one meets this type with such extra¬ ordinary frequency among Indians, Mexicans, and negroes
Fig. 11. BALL AND FIELD TEST. M. P„ AGE 14; MENTAL AGE 10-8
92 THE MEASUREMENT OF INTELLIGENCE
suggests quite forcibly that the whole question of racial differences in mental traits will have to be taken up anew and by experimental methods. The writer predicts that when this is done there will be discovered enormously sig¬ nificant racial differences in general intelligence, differ¬ ences which cannot be wiped out by any scheme of mental culture.
Children of this group should be segregated in special classes and be given instruction which is concrete and prac¬ tical. They cannot master abstractions, but they can often be made efficient workers, able to look out for themselves. There is no possibility at present of convincing society that they should not be allowed to reproduce, although from a eugenic point of view they constitute a grave prob¬ lem because of their unusually prolific breeding.
Dull normals (I Q usually 80 to 90). In this group are included those children who would not, according to any of the commonly accepted social standards, be considered feeble-minded, but who are nevertheless far enough below the actual average of intelligence among races of western European descent that they cannot make ordinary school progress or master other intellectual difficulties which average children are equal to. A few of this class test as low as 75 to 80 I Q, but the majority are not far from 85. The unmistakably normal children who go much below this (in California, at least) are usually Mexicans, Indians, or negroes.
R. G. Negro boy , age 13-5; mental age 10-6; I Q approximately 80. Normal in appearance and conduct, but very dull. Is attempt¬ ing fifth-grade work in a special class, but is failing. From a fairly good home and has had ordinary school advantages. In the exam¬ ination his intelligence is very even as far as it goes, but stops rather abruptly after the 10-year tests. Will unquestionably pass as normal among unskilled laborers, but his intelligence will never
INTELLIGENCE QUOTIENT SIGNIFICANCE 95
exceed the 12-year level and he is not likely to advance beyond the seventh grade, if as far.
F. D. Boy, tested at age 10-2; I Q 83, and again at 1J/.-1; I Q. 79.
Mental age in the first test was 8-6 and in the second test 11. Son of a barber. Father dead; mother capa¬ ble; makes a good home, and cares for her children well. At 10 was doing unsatisfactory work in the fourth grade, and at 12 unsatisfac- Fl°- 12- BALI' AND FIELD- R- G-, tory work in low sixth. Good- AGE 13"* MENTAL AGE 1(Hi looking, normal in appearance and social development, and though occasionally obstinate is usually steady. Any one unacquainted with his poor school work and low I Q would consider him per¬ fectly normal. No physical or moral handicaps of any kind that could possibly account for his retardation. Is simply dull. Needs purely a vocational training, but may be able to complete the eighth grade with low marks by the age of 16 or 17.
G. G. Girl, age 12-4; mental age 10-10; 1 Q 82. From average home. Excellent educational advantages and no physical handi¬ caps. At 12 years was doing very poor work in fifth grade. Appear¬ ance, play life, and attitude toward other children normal. Simply dull. Will probably never go beyond the 12- or 13-year level and is not likely to get as far as the high school.
Those testing 80 and 90 will usually be able to reach the eighth grade, but ordinarily only after from one to three or four failures. They are so very numerous (about 15 per cent of the school enrollment) that it is doubtful whether we can expect soon to have special classes enough to ac¬ commodate all. The most feasible solution is a differen¬ tiated course of study with parallel classes in which every child will be allowed to make the best progress of which he is capable, without incurring the risk of failure and non-
94 THE MEASUREMENT OF INTELLIGENCE
promotion. The so-called Mannheim system, or something similar to it, is what we need.
Average intelligence (I Q 90 to 110). It is often said that the schools are made for the average child, but that “ the average child does not exist.” He does exist, and in very large numbers. About 60 per cent of all school children test between 90 and 110 I Q, and about 40 per cent between 95 and 105. That these children are average is attested by their school records as well as by their I Q’s. Our records show that, of more than 200 children below 14 years of age and with I Q between 95 and 105, not one was making much more nor much less than average school progress. Four were two years retarded, but in each case this was due to late start, illness, or irregular attendance. Children who test close to 90, however, often fail to get along satisfactorily, while those testing near 110 are oc¬ casionally able to win an extra promotion.
The children of this average group are seldom school problems, as far as ability to learn is concerned. Nor are they as likely to cause trouble in discipline as the dull and border-line cases. It is therefore hardly necessary to give illustrative cases here.
The high school, however, does not fit their grade of in¬ telligence as well as the elementary and grammar schools. High schools probably enroll a disproportionate number of pupils in the I Q range above 100. That is, the average in¬ telligence among high-school pupils is above the average for the population in general. It is probably not far from 110. College students are, of course, a still more selected group, perhaps coming chiefly from the range above 115. The child whose school marks are barely average in the ele¬ mentary grades, when measured against children in general, will ordinarily earn something less than average marks in high school, and perhaps excessively poor marks in college.
INTELLIGENCE QUOTIENT SIGNIFICANCE 95
Superior intelligence (I Q 110 to 120). Children of this group ordinarily make higher marks and are capable of making somewhat more rapid progress than the strictly average child. Perhaps most of them could complete the eight grades in seven years as easily as the average child does in eight years. They are not usually the best scholars, but on a scale of excellent, good, fair, poor, and failure they will usually rank as good, though of course the degree of application is a factor. It is rare, however, to find a child of this level who is positively indolent in his school work or who dislikes school. In high school they are likely to win about the average mark.
Intelligence of 110 to 120 I Q is approximately five times as common among children of superior social status as among children of inferior social status; the proportion among the former being about 24 per cent of all, and among the latter only 5 per cent of all. The group is made up largely of children of the fairly successful mercantile or professional classes.
The total number of children between 110 and 120 is almost exactly the same as the number between 80 and 90; namely, about 15 per cent. The distance between these two groups (say between 85 and 115) is as great as the distance between average intelligence and border-line deficiency, and it would be absurd to suppose that they could be taught to best advantage in the same classes. As a matter of fact, pupils between 110 and 120 are usually held back to the rate of progress which the average child can make. They are little encouraged to do their best.
Very superior intelligence (I Q 120 to 140). Children of this group are better than somewhat above average. They are unusually superior. Not more than 3 out of 100 go as high as 125 I Q, and only about 1 out of 100 as high as 130.
96 THE MEASUREMENT OF INTELLIGENCE
In the schools of a city of average population only about 1 child in 250 or 300 tests as high as 140 I Q.
In a series of 476 unselected children there was not a single one reaching 120 whose social class was described as “below average.”1 Of the children of superior so¬ cial status, about 10 per cent reached 120 or better. The 120-140 group is made up almost entirely of children whose parents belong to the professional or very successful business classes. The child of a skilled laborer belongs here occasionally, the child of a common laborer very rarely indeed. At least this is true in the smaller cities of California among populations made up of native-born Americans. In all probability it would not have been true in the earlier history of the coun¬ try when ordinary labor was more often than now per¬ formed by men of average intelligence, and it would probably not hold true now among certain immigrant populations of good stock, but limited social and educa¬ tional advantages.
What can children of this grade of ability do in school? The question cannot be answered as satisfactorily as one could wish, for the simple reason that such children are rarely permitted to do what they can. What they do accom¬ plish is as follows: Of 54 children (of the 1000 unselected cases) falling in this group, 12 x/l per cent were advanced in the grades two years, approximately 54 per cent were ad¬ vanced one year, 28 per cent were in the grade where they belonged by chronological age, and three children, or 5)4 per cent, were actually retarded one year. But wherever located, such children rarely get anything but the highest marks, and the evidence goes to show that most of them could easily be prepared for high school by the age of 12
1 In other investigations, however, we have found even brighter chil¬ dren from very inferior homes. See p. 117 for an example.
J
INTELLIGENCE QUOTIENT SIGNIFICANCE 97
years. Serious injury is done them by schools which believe in “ putting on the brakes.”
The following are illustrations of children testing be¬ tween 130 and 145. Not all are taken from the 1000 un¬ selected tests. The writer has discovered several children of this grade as a result of lectures before teachers’ insti¬ tutes. It is his custom, in such lectures, to ask the teachers to bring in for a demonstration test the “ brightest child in the city ” (or county, etc.). The I Q resulting from such a test is usually between 130 and 140, occasionally a little higher.
Examples of very superior intelligence
Margaret P. Age 8-10; mental age 11-1; I Q 130. Father only a skilled laborer (house painter), but a man of unusual intelligence and character for his social class. Home care above average. M. P. has attended school a little less than three years and is completing fourth grade. Marks all “excellent.” Health perfect. Social and moral traits of the very best. Is obedient, conscientious, and un¬ usually reliable for her age. Quiet and confident bearing, but no touch of vanity.
M. P. is known to be related on her father’s side to John Wesley, and her maternal grandfather was a highly skilled mechanic and the inventor of an important train-coupling device used on all railroads.
Although she is not yet 9 years old and is completing the fourth grade, she is still about a grade below where she belongs by mental age. She could no doubt easily be made ready for high school by the age of 12.
J. R. Girl, age 12-9; mental age 16 ( average adult); I Q approxi¬ mately 130. Daughter of a university professor. In first year of high school. From first grade up her marks have been nearly all of the A rank. For first semester of high school four of six grades were A, the others B. A wonderfully charming, delightful girl in every respect. Play life perfectly normal.
J. R.’s parents have moved about a great deal and she has at¬ tended eight different schools. She is two years above grade in school, but of this gain only one-half grade was made in school;
98 THE MEASUREMENT OF INTELLIGENCE
the other grade and a half she gained in a little over a year by staying out of school and working a little each day under the instruction of her mother. But for this she would doubtless now be in the seventh grade instead of in high school. As it is she is at least a grade below where she belongs by mental age. Something better than an average college record may be safely predicted for J. R.
E. B. Girl, age 7-9; mental age 10-2; I Q ISO. E. B. was selected by the teachers of a small California city as the brightest school child in that city (school population about 500). Her parents are
said to be unusually intelligent. E. B. is in the third grade, a year ad¬ vanced, but her mental level shows that she belongs in the fourth. The test was made as a demonstration test in the presence of about 150 teachers, all of whom were charmed by her delightful personality and keen responses. No trace of vanity or queerness of any kind. Health excellent. E. B. ought to be ready for high school at 12; she will really Fia. is. BALL AND FIELD TEST, have the intelligence to do high- E. B., AGE 7-9-, I Q iso school work by 11.
L. B. Girl, age 8-6; mental age 11-6; I Q 135. Tested nearly three years earlier, age 5-11; mental age 7-6; I Q 127. Daughter of a university professor. At age of 8-6 was doing very superior work in the fifth grade. Later, at age of 10-6, is in the seventh grade with all her marks excellent. Has two sisters who test almost as high, both completing the eighth grade at barely 12 years of age. L. B. looks rather delicate, and though a little nervous is ordinarily strong. We have known her since her early childhood. Like both her sisters, she is a favorite with young and old, as nearly perfection as the most charming little girl could be.
R. S. Boy, age 6-6; mental age 9-6; I Q lf8. When tested at age 5-2 he had a mental age of 7-6, I Q 142. Father a university professor. R. S. entered school at exactly 6 years of age, and at the present writing is 7Yi years old and is entering the third grade. Leads his class in school and takes delight in the work. Is normal
INTELLIGENCE QUOTIENT SIGNIFICANCE 99
in play life and social traits and is dependable and thoughtful be¬ yond his years. Should enter high school not later than 12; could probably be made ready a year earlier, but as he is somewhat nervous this might not be wise.
T. F. Boy, age 10-6; mental age If; I Q 133. At 13-6 tested at “superior adult,” and had vocabulary of 13,000 (also “superior adult”). Son of a college professor. Did