The Measurement of Intelligence.

by Lewis Madison Terman.

INTRODUCTION

The present volume appeals to the editor of this series as one of the most significant books, viewed from the standpoint 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 understand, 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 procedure of giving them. In a clear and easy style the author sets forth scientific facts of far-reaching educational importance, facts which it has cost him, his students, and many other scientific workers, years of painstaking labor to acc.u.mulate.

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 educational 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 methods 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 procedure, the grading of pupils, promotional schemes, the study of the r.e.t.a.r.dation of children in the schools, juvenile delinquency, 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 practices, and in particular for diagnosing individual possibilities and needs. Just now the method is new, and its use somewhat 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 schoolroom procedure as a blood-count now is in physical diagnosis. That our schoolroom methods will in turn become much more intelligent, and that all cla.s.ses of children, but especially 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 sufficient skill to enable teachers and school princ.i.p.als to give such tests intelligently is not especially difficult to acquire. This being the case it may be hoped that the requisite 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 intelligence scale in public schools, inst.i.tutions for defectives, reform schools, juvenile courts, and police courts is sufficient evidence of the intrinsic worth of the method. It is generally recognized, however, that the serviceableness of the scale has. .h.i.therto 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 instructions 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 purposes 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 detail. A general acquaintance with the nature of the individual tests is by no means sufficient.

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 procedure as described in Part II, should be sufficient to prepare 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 a.s.sistance this book could not have been written.

STANFORD UNIVERSITY, _April, 1916_.

PART I

PROBLEMS AND RESULTS

THE MEASUREMENT OF INTELLIGENCE

CHAPTER I

THE USES OF INTELLIGENCE TESTS

INTELLIGENCE TESTS OF r.e.t.a.r.dED SCHOOL CHILDREN. Numerous studies of the age-grade progress of school children have afforded convincing evidence of the magnitude and seriousness of the r.e.t.a.r.dation 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 r.e.t.a.r.ded two years or more; and that from 5 to 8 per cent are r.e.t.a.r.ded 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-teaching 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 individualizing of instruction, by improved methods of promotion, by increased attention to children's health, and by other reforms 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 a.s.sumption that under the right conditions all children would be 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 cla.s.sed as normal, vast individual differences have been found to exist in original mental endowment, differences which affect profoundly the capacity to profit from school instruction.

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. Instead of wasting energy in the vain attempt to hold mentally 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 r.e.t.a.r.dation which involves failure and the repet.i.tion 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, he studies the materials to be used, and learns by means of tests exactly the amount of strain per unit of size his materials will be able to withstand. He does not work empirically, 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 forethought 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 examination takes less than one hour, and the result will contribute more to a real understanding of the case than anything 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 cla.s.ses, if they are to be made the dumping-ground for all kinds of troublesome cases--the feeble-minded, the physically defective, the merely backward, the truants, the incorrigibles, etc. Without scientific diagnosis and cla.s.sification of these children the educational work of the special cla.s.s must blunder along in the dark. In such diagnosis and cla.s.sification our main reliance must always be in mental tests, properly used and properly interpreted.

INTELLIGENCE TESTS OF THE FEEBLE-MINDED. Thus far intelligence tests have found their chief application in the identification 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 intelligently upon either the content or the method of instruction 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 a.s.sociated with this term. The earlier methods of diagnosis caused a majority of the higher grade defectives to be overlooked. Previous 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 considerable 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 becomes 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 difficult 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 combinations but they cannot be taught to meet new conditions 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 defectives under the surveillance and protection of society. This will ultimately result in curtailing the reproduction of feeble-mindedness and in the elimination of an enormous amount of crime, pauperism, and industrial inefficiency.

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 a.s.sume.

INTELLIGENCE TESTS OF DELINQUENTS. One of the most important facts brought to light by the use of intelligence tests is the frequent a.s.sociation 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 underestimated even by the most competent students of criminology.

The criminologists have been accustomed to give more attention 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 criminality, but the physical accompaniments of feeble-mindedness. They have no diagnostic significance except in so far as they are indications of mental deficiency. Without exception, every study which has been made of the intelligence 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 p.r.o.nouncement "intellect sound."

Under the direction of Dr. G.o.ddard the Binet tests were given to 100 juvenile court cases, chosen at random, in Newark, New Jersey. Nearly half were cla.s.sified 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 G.o.ddard, 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 Ma.s.sachusetts 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, Pennsylvania, 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 inst.i.tution one of the most important research laboratories of the kind in the United States, with a trained psychologist, Dr. Mabel Fernald, in charge.

Of 564 prost.i.tutes investigated by Dr. Anna Dwyer in connection with the Munic.i.p.al 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.