The Project Gutenberg eBook, Deficiency and Delinquency, by James Burt Miner

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Educational Psychology Monographs

This volume, which is No. 21 in the Series, was

edited by J. Carleton Bell

Deficiency and Delinquency
An Interpretation of Mental Testing

BY

JAMES BURT MINER, LL.B., PH.D.

Associate Professor of Applied Psychology, Carnegie Institute of Technology, Pittsburgh; sometime lecturer at the school for teachers of special classes, Minnesota State School for the Feeble-Minded

BALTIMORE

WARWICK & YORK, Inc.

1918

Copyright, 1918

Warwick & York, Inc.

DEFICIENCY AND DELINQUENCY

TABLE OF CONTENTS

LIST OF TABLES AND FIGURES

DEFICIENCY AND DELINQUENCY

PREFACE

In undertaking in 1912 to examine the mental development of delinquents for the clinic started and supported by the Juvenile Protective League of Minneapolis, in connection with the Juvenile Court, I soon became convinced that a safer method for evaluating the limit of feeble-mindedness with tests was more needed than masses of new data. The researches that have been published in the past three years do not seem to have changed this situation. Numerous studies with psychological tests are already available, but they generally treat of average rather than borderline conditions. In the field of delinquency the work of testing has been carried on with especial activity. Here, as well as elsewhere, the conclusions seem likely to be misleading unless social workers better appreciate the real place of mental tests, their value and their limitations.

The tables of a few hundred juvenile delinquents and school children examined in Minneapolis, which are presented in this book, indicate the occasion rather than the aim of the present study. The purpose is mainly to help clear the ground for other work with mental tests, and especially to put the determination of feeble-mindedness by objective examination with the Binet or other scales on what seems to me a sounder basis. Furthermore, the results of objective testing which have been so rapidly accumulating in the field of delinquency need to be assembled and reorganized in order to avoid confusion. It is especially desirable to discover a conservative basis for objective diagnosis of deficient intellectual capacity in order to prevent very useful testing systems from becoming unjustly discredited and to preserve the advance that has been made.

The work out of which this monograph grew was begun through the encouragement of Judge Edward F. Waite of the Hennepin County Juvenile Court. His earnest co-operation and my interest in the field of mental testing has led me to continue the study. Judge Waite's insight into his court problems resulted in the early organization of a Juvenile Court clinic (153, 170) in Minneapolis. The clinic is in charge of Dr. Harris Dana Newkirk, who has contributed materially to this study by his thorough medical examination of each of the cases brought to him. To the staff at the probation office I am also much indebted.

The earnest help of Superintendent D. C. MacKenzie, of the Glen Lake Farm School for the juvenile delinquents of Hennepin County, made a close study of our most interesting group of boys much more profitable personally than I have shown here. For detailed expert work in tabulation and in examinations I wish to express my thanks to my advanced students, a half dozen of whom have contributed materially to the data of this book.

James Burt Miner.

Carnegie Institute of Technology

Pittsburgh, Pa.

CHAPTER I. INTRODUCTION

As an interpretation of the results which have been obtained with mental tests, this book lies between the topics of deficiency and delinquency. It is an attempt to discover the significance of objective measurements of ability in connection with both of these fields. The pressing practical problem was to find out what positions on a scale for testing mental development were symptomatic of social deficiency. After working out a percentage method for conservatively indicating these borderlines for tested deficiency, it was then possible to reinterpret the test records of over 9000 delinquents who have been examined with some form of the well-known Binet Scale. The size of the problem of the deficient delinquent has thus been determined on a significant scientific plan. The outcome is a new basis for judging the current statements about this problem by those who have used the Binet scale. Scores of investigators by their tireless energy have provided data which may now be compared for many types of delinquents and in many parts of the country. Some sixty studies of deficient delinquents have been thus summarized from the point of view of psychological tests.

Closely related to the problem of the frequency of feeble-mindedness among delinquents is the question of the cause of delinquency. This has further been considered in the light of the most important scientific studies, especially those using the method of correlation. Among these researches stands out the fundamental investigation of the causes of criminality by Goring, a work which has received very inadequate attention in this country, although it involved ten years study of a group of 3000 convicts by the best quantitative methods. The careful study of these objective investigations should take the question of the relation of deficiency and delinquency out of the realm of opinion and theory. It may be expected to have an important influence upon the social handling of these problems. In this connection I have added a chapter of suggestions which have grown out of my year's study of the education of deficients and delinquents in European schools and institutions.

To determine the size of the problem of dealing with deficients, especially deficient delinquents, is a task of first importance. In spite of our more conservative basis for judging the results with tests, the necessity of caring for the feeble-minded remains the most vital problem connected with social welfare. The movement for more individual training in our schools, which has been gaining such headway, may also be encouraged by the evidence that maladjustment to school work is also definitely related to delinquency.

It is essential that we should have objective data for determining the borderline of tested deficiency among adults. To meet the present serious lack of knowledge on this point, new data were collected which for the first time afford the means of determining, by the use of a randomly selected group what is a conservative borderline of tested deficiency for those intellectually mature. These data include the Binet test records for all the 15-year-old children who resided in seven school districts in Minneapolis and who had not graduated from the eighth grade.

The urgency of plans for indefinitely segregating certain types of the feeble-minded, especially deficient delinquents, has placed a new emphasis on those quantitative aids to diagnosis. The difficulty of establishing feeble-mindedness before a court has been called to attention by both Supt. C. A. Rogers ([173])[^[1]] of the Minnesota School for Feeble-Minded, and Supt. Walter E. Fernald ([104]) of the Massachusetts School. Both of these men recognize that psychological tests are the most hopeful way of improving this situation.

A fundamental feature of the diagnosis of deficiency is the plan here advocated for designating the borderlines on a scale on the basis of a percentage definition of tested deficiency. This involves the distinction of intellectual deficiency from certain rare volitional forms of feeble-mindedness, which the tests do not at present detect. This percentage definition seems to afford the best approach to a test diagnosis. It is apparent that the data are insufficient for finally establishing such a quantitative description of the lower limit for passable intellects on a mental scale. The plan, however, may be easily adjusted to new data, and meanwhile avoids some of the serious current misinterpretations of test results.

While the idea of a quantitative definition of the borderline of deficiency is not new, the percentage method seems to have certain fundamental advantages over either the “intelligence quotient” of Stern ([188]), the “intelligence coefficient” of Yerkes ([226]), or the description in terms of deviation, mentioned by Norsworthy ([159]) and Pearson (164, 166, 167). Several investigators, including Terman ([57]) and Yerkes ([226]), are utilizing the percentage method indirectly for describing the borderline of feeble-mindedness, but have inadequately distinguished it from the ratios. While ratio and deviation methods are possibly more serviceable for certain purposes, they are especially faulty near the borderline of deficiency, since they are affected by variations in the units of measurement and in the form of distribution from age to age. My paper on a percentage definition and the detailed plan for determining the borderline in the Binet scale, which was read at the meeting of the American Psychological Association in 1915, seems to have been contemporaneous with a similar suggestion by Pintner and Paterson ([44]). They, however, would restrict the term “feeble-mindedness” to tested deficiency, while I advocate the use of percentage borderlines on a test scale as symptomatic of one form of feeble-mindedness, much as excess of normal temperature on a clinical thermometer is symptomatic of disease.

Although no system of objective tests will ever dispense with the need for expert interpretation in diagnosing individual cases, still there are few who would doubt that it is desirable to reduce the option of expert judgment as much as we reasonably can. This is the scientific method of procedure. The borderline cases, however, which are often most troublesome in their delinquencies, are just those which will longest defy rigid rules. The diagnostician who wants to be as free as possible from external restraint will find in this border field of mental capacity a happy hunting ground. His scientific instincts should make him eager to discover when he leaves the mundane sphere and sallies forth into uncharted realms where he bears the full responsibility of his own opinion. Let me hasten to add that reasoning from objective data in the mass to the diagnosis of an individual case may lead to serious mistakes, unless one keeps alert to detect the exception from the general rule, and unless one understands the numerous sources of error entering into an examination. On the other hand the test results when properly interpreted afford the most important criteria on which to base a prognosis if they are considered in relation to the history of the case and the medical examination.

By the use of more conservative borderlines for raising the presumption of deficiency and also by designating a doubtful position on the scale, on the plan advocated herein, it is possible to make scales for testing mental capacity more serviceable both to the clinician and to the amateur tester. The latter may use the scales for his own information or may wish to discover whether an examination by an expert in mental development is desirable, without attempting to make a diagnosis himself. The scale may thus take a place in the study of child mentality analogous to the familiar Snellen chart in the testing of vision. For every teacher familiarity with a development scale may thus become as essential and desirable as the knowledge of the chart for eye testing. It should find a place in all progressive schools which do not have the services of a clinician.

The Binet system of tests was used for obtaining new data on groups of juvenile delinquents in Minneapolis and Pittsburgh. The use of this scale, around which the discussion centers, grew out of the necessity for immediate practical results for the clinic at the Minneapolis Juvenile Court which I was called upon to serve. In 1912, when that work began, there was practically nothing approaching norms with children for any other scale of tests. Even today it is plain that there is more data available for interpreting results with the Binet scale than with any other system of tests. While my experience would make me unwilling to advocate the Binet tests as an ideal method for building up a measuring scale, I still feel that it remains the most useful method at present for discovering the fundamental symptoms of intellectual deficiency. The percentage method, here advocated, as the best way available for determining the borderlines with a scale, would be quite as serviceable, however, with any other testing system. It has been my aim to contribute to the interpretation of the results of the tests as they are, not to perfecting the arrangement or details of the separate tests.[^[2]] It happens that one of the main objections which has been raised to the Binet scale, the inadequacy of its tests for the older ages, loses its force so far as the diagnosis of feeble-mindedness is concerned for those who accept the borderlines described in this paper.

Some diagnosticians may hesitate to use the Binet scale because of the criticisms it has received. Yerkes and Bridges state: “Indeed, we feel bound to say that the Binet scale has proved worse than useless in a very large number of cases” (226, p. 94). So far as this objection arises from the attempt to use the descriptions of the borderline of feeble-mindedness published with Binet scales, it will meet with a wide response. The difficulty is hardly less, as I shall show, with other scales. The definition of the borderline is certainly the vital point with any objective method for aiding diagnosis. Only by improving methods for determining the borderline can this weakness be attacked. The central contribution of this paper is directed, therefore, to this problem of the interpretation of the borderline, so that objective scales may be made more reliable for purposes of diagnosis.

In Part Two I have added an intensive discussion of the measurement of development and a comparison of the different objective methods for describing the borderline. This may well be omitted by those who are not interested in the technical aspects of these questions. To those who care only for accounts of individual lives, let me say that I am contributing nothing herein to that important field which has been covered in authoritative form by Dr. Healy ([27]) and by Dr. Goddard ([112]). They will find instead, I hope, the fascination of figures, a picture book in which probability curves take the place of photographs and biographies, in which general tendencies are evaluated and attention is focussed upon the problem of properly diagnosing deficiency and upon plans for the care of the feeble-minded, whether they be potential or actual delinquents.

[1]. Numbers in parenthesis indicate the references in the bibliography at the close of the book.

[2]. Those concerned with other features of the Binet scale will find an admirable bibliography by Samuel C. Kohs, Journal of Educational Psychology, April, May and June, 1914, and September, October, November, and December, 1917. Other references are contained in the Bibliography by L. W. Crafts ([9]).

PART ONE
PRACTICAL CONSIDERATIONS

CHAPTER II. THE FUNCTIONS OF A SCALE IN DIAGNOSIS

A. The Meaning of Intellectual Deficiency.

Whatever form the definition of feeble-mindedness may take, in this country at least[^[3]] the concept has become quite firmly established as describing the condition of those who require social guardianship, because, with training, they do not develop enough mentally to live an independent life in society. The feeble-minded are socially deficient because of a failure to develop mentally. They are proper wards of the state because of this mental deficiency. Goddard says, they are “incapable of functioning properly in our highly organized society” (112, p. 6). The most generally quoted verbal description of the upper line of social unfitness is that of the British Royal Commission on Feeble-Mindedness: “Persons who may be capable of earning a living under favorable circumstances, but are incapable from mental defect existing from birth or from an early age (a) of competing on equal terms with their normal fellows; or (b) of managing themselves and their affairs with ordinary prudence.” It is clear that the intention is to distinguish mental deficiency from senile dementia, from hysteria and from insanity, in which there is a temporary or permanent loss of mental ability rather than a failure to develop. Feeble-mindedness may, however, arise from epilepsy or from other diseases or accidents in early life as well as from an inherent incapacity for development. Moreover, mental deficiency, or feeble-mindedness, (I use the terms interchangeably) does not imply that the social unfitness is always caused by intellectual deficiency. Mind is a broader term than intellect, as we shall note in the next section.

This definition of the feeble-minded is the main idea expressed by Witmer ([221]), Tredgold ([204]), Pearson ([164]), and Murdock ([164]). The historical development of the concept is traced by Rogers ([172]) and Norsworthy ([159]). It is criticized by Kuhlmann ([140]) as impractical and indefinite. The indefiniteness is indicated by such terms as “under favorable circumstances,” “on equal terms,” and “with ordinary prudence.” This objectionable uncertainty as to social fitness can be considerably relieved for those types of feeble-mindedness which involve the inability to pass mental tests, since this result can later be correlated with subsequent social failure and predictions made during childhood on the basis of the tests. Attempts to make the concept of feeble-mindedness more definite have, therefore, naturally taken some quantitative form in relation to objective tests. Binet and the French commission in 1907 ([77]) called attention to the method in use in Belgium for predicting unfitness objectively on the basis of the amount of retardation in school at different ages. With the appearance in 1908 of the Binet-Simon revised scale for measuring mental development, quantitative descriptions began to be concerned with the borderlines of mental deficiency on scales of tests.

While the quantitative descriptions of tested deficiency do not include all forms of feeble-mindedness, as I shall show in the next section, they have made the diagnosis of the majority of cases much more definite. Nobody would think of returning to the days when the principal objective criteria were signs of Cretinism, Mongolianism, hydrocephalus, microcephalus, epilepsy, meningitis, etc., which LaPage ([141]) has shown are not found among more than 9% of 784 children in the Manchester special schools. The impossibility of agreeing upon subjective estimates of mental capacity without the use of objective criteria is well shown by Binet's methodical comparison of the admission certificates filled out within a few days of each other by the alienists for the institutions of Sainte-Anne, Bicêtre, the Salpêtreire and Vaucluse. These physicians gave their judgments as to whether a case was an idiot, imbecile or higher grade. Binet says: “We have compared several hundreds of these certificates, and we think we may say without exaggeration that they looked as if they had been drawn by chance out of a sack” (77, p. 76).

The rapid accumulation of data with psychological tests has made it possible to take our first halting steps in the direction of greater definiteness in diagnosis by a larger use of objective methods. This increase in significance of the concept of deficiency is fruitful at once in estimating the size of the social problem and planning means for undertaking the care of these unfortunates. We can discover something of the error in the previous subjective estimates of the frequency of feeble-mindedness. We can bring together and compare the work of different investigators, not only in our country, but throughout the world. We can discover, for example, how important the problem of deficiency is among different groups of delinquents, knowing that the differences are not to be explained by differences in expert opinion. Furthermore, we can now determine, with considerable accuracy, whether the diagnosis made by a reliable examiner is independent of his personal opinion.

If we disregard the natural antipathy of many people to anything which tends to limit the charming vagueness of their mental outlook, we may endeavor to chart this horizon of tested deficiency with something of the definiteness of figures, which shall at the same time indicate a range of error. As soon as our aim comes to be to plot the borderline on a measuring scale of mental ability, we find that the borderline must be so stated that we can deal with either adults or children. Two sorts of limiting regions must be described, one for mature minds and one for immature minds. The latter will be in the nature of a prediction as to what sort of ability the children will show when they grow up. We must keep in mind, therefore, that we should attempt our quantitative definition for both growing and adult minds. As soon as the growing mind passes the lower limit for the mature it is then guaranteed access to the social seas although it may never swim far from shore nor develop further with advancing years. In seeking greater definiteness, our aim should then be to describe both the limit for the mature individuals and the limit for the immature of each age. In this paper the definition will be restricted to intellectual deficiency, i. e., tested deficiency. It will take the form of describing the positions on a scale below which fall the same lowest percentage of intellects. This percentage definition of intellectual deficiency offers such a simple method of consistently describing the borderlines for mature and immature that it is surprising so little attempt has previously been made to work it out for a system of tests. Although the principle on which the definition is based depends upon the distribution curve of ability, it is concerned only with the lower limit of the distribution. Since the exact form of this distribution is uncertain I have preferred to call it a percentage definition of intellectual deficiency rather than to state the limits in terms of the variability of ability. Moreover the lowest X per cent. in mental development requires no further explanation to be understood by the layman.

B. Forms of Mental Deficiency Not Yet Discoverable by Tests.

The first broad conclusion that impresses those who try to use mental scales for diagnosing feeble-mindedness is that the lower types, the idiots and imbeciles, can be detected with great accuracy by an hour's testing. The difficulties pile up as soon as the individual rises above the imbecile group. The practical experience of those in institutions for the feeble-minded here becomes of fundamental importance. They are able to supply the history of exceptions that should make us cautious about our general rules. Certain people whom they have known for years to be unable to adjust themselves socially because their minds have not reached the level of social fitness will yet be able to pass considerably beyond the lower test limit for mature minds. The mental scales can only detect those feeble-minded who cannot succeed with our present tests. This is the basal principle in using any system of tests.

Stated in another way, this first caution for anybody seeking the assistance of a mental scale is that tests may detect a feeble-minded person, but when a person passes them it does not guarantee social fitness. The negative conclusion, “this person is not feeble-minded,” can not be drawn from tests alone. Mental tests at present are positive and not negative scales. This fact will probably always make the expert's judgment essential before the discharge of a suspected case of mental deficiency. When a subject falls below a conservative limit for tested ability a trained psychologist who is familiar with the sources of error in giving tests, even without experience with the feeble-minded, should be able to say that this person at present shows as deficient development as the feeble-minded. To conclude however that any subject has a passable mind requires in addition practical experience with feeble-minded people who pass the tests. It is very much easier to state that the tests do not detect all forms of feeble-mindedness than it is to give any adequate description of the sort of feeble-mindedness which they do not as yet detect.

This distinction between the feeble-minded who do well with test scales and those who do not, is well known in the institutions for the feeble-minded. Binet sought to distinguish some of the feeble-minded who escaped the tests by calling them “unstable,” or “ill-balanced,” individuals as Drummond ([77]) translates the term. To use the historical distinctions of psychology, their minds seem to be undeveloped more on their volitional and emotional sides than on their intellectual side. Weidensall ([59]) has described another type as “inert.” She found that quite a number of the reformatory women might slide through the tests but fail socially from the fact that “their lives and minds are so constituted that they feel no need to learn the things any child ought to know, though they can and do learn when we teach them.” Again, it seems to be a disturbance of will through the feeling, rather than an intellectual deficiency. Many of the so-called “moral imbeciles” are probably able to pass intellectual tests lasting but a few minutes. Like the unstable or inert they are not failures because of a lack of intellectual understanding of right and wrong, but because of excess or deficiency of their instinctive tendencies especially in the emotional sphere. Such weakness of will may arise either from abnormality of specific instinctive impulses or inability to organize these impulses so that one impulse may be utilized to supplement or inhibit another. We may call all this group of cases socially deficient because of a weakness in the volitional, or conative, aspect of mind.

The discrimination of mental activities which are predominately emotional and conative from those in which intellect is mainly emphasized is also well recognized by those who have been making broad studies of tests in other fields than that of feeble-mindedness. Hart and Spearman ([123]), for example, call attention to the fact that tests passed under the stimulus of test conditions represent what the subject does when keyed up to it rather than what he would do under social conditions. We cannot be sure that speed ability as tested will represent speed preferences. The subject may be able to work rapidly for a few minutes, but in life consistently prefer to work deliberately. Regarding the eighteen tests which they studied with normal and abnormal adults they say: “These tests have been arranged so as to be confined to purely intellectual factors. But in ordinary life, this simplicity is of rare occurrence. For the most part, what we think and believe is dominated by what we feel and want.” Kelley ([130]) finds by the regression equation that the factor of effort amounts to two-thirds of the weight of that of the intellectual factor in predicting scholarship from teachers' estimates. Webb ([217]) thinks that he finds by tests a general conative factor comparable to Spearman's general intellective factor.

With the change in point of view that has come from the adoption of the biological conception of the mind the discrimination of the different forms of feeble-mindedness must be recognized as a distinction in the emphasis on intellectual, emotional and conative processes, not a distinction between actually separable forms of mental activity. On account of the organic nature of the mind it is well established that various mental processes are mutually dependent. Any disturbance of the emotional processes will tend to affect the thinking and vice versa. Even if we believe that emotions are complex facts, involving vague sensations as well as feelings, and that terms like emotion, memory, reasoning and will are names for classes of mental facts rather than for mental powers, it still remains important to distinguish between feeling, intellect and will, as well as to recognize the interdependence of the mental processes. Common sense seems to agree with psychological descriptions in regarding mind as a broader term than intellect, and feeble-mindedness as a broader term than intellectual feebleness.

Since tests at present tend to reach the intellectual processes more surely than the emotional, we describe those who fail in them as intellectually deficient. The term “intellect” seems to be better than “intelligence” because the latter seems to include information as well as capacity, while the aim of measuring scales has been to eliminate the influence of increasing information with age. To be thoroughly objective, of course, one should talk about “feebleness in tested abilities;” but we would then fail to point out the important fact about our present scales that they detect mainly intellectual deficiency, that they do not reach those forms of feeble-mindedness in which the weakness in such traits as stability, ambition, perseverance, self-control, etc., is not great enough to interfere with the brief intellectual processes necessary for passing tests. Intellectual deficiency will be used hereafter to refer to those social deficients whose feebleness is disclosed by our present test scales.

In the opinion of Kuhlmann these cases of disturbed emotions and will which shade off into different forms of insanity should not be classed as feeble-minded at all, although he recognizes that they are commonly placed in this group. He regards them as an intermediate class between the feeble-minded and the insane. He says: “They readily fail in the social test for feeble-mindedness and because of the absence of definite symptoms of insanity are often classed as feeble-minded. In the opinion of the present writer they should not be so classed, because they require a different kind of care and treatment, and have a different kind of capacity for usefulness” ([140]). So long as this group of what we shall term “conative cases” is discriminated from the intellectually deficient it matters less whether they be regarded as a sub-group of the feeble-minded or as a co-ordinate class. In grouping them with the feeble-minded we have followed the customary classification. An estimate of the size of this group will be considered later in Chapter III.

C. Doubtful Intellects Accompanied by Delinquency Presumed Deficient.

Conative forms of feeble-mindedness are perhaps the most serious types in the field of delinquency. They are the troublesome portion of the borderland group of deficient delinquents about which there is so much concern. It is important to remember that it is just among these cases that the test judgment is least certain. In this dilemma one principle seems to be sound enough psychologically to be likely to meet with acceptance. I should state this principle as follows: A borderline case which has also shown serious and repeated delinquency should be classed as feeble-minded, the combination of doubtful intellect and repeated delinquency making him socially unfit. This will relieve the practical situation temporarily until tests are perfected which will detect those whose feebleness is specialized in those phases of volition centering around the instinctive passions, control, balance, interest and endurance. The principle recognizes that mental weakness is sometimes emphasized in the volitional processes of the mind.

The principle is apparently in conflict with the rule advocated by Dr. Wallin. Referring to the mental levels reached by individuals, he says: “We cannot consider X-, XI-, or XII-year-old criminals as feeble-minded because they happen to be criminals and refuse to consider X-, XI-, and XII-year-old housewives, farmers, laborers and merchants as feeble-minded simply because they are law abiding and successful” (214, p. 707). At another place he insists “that the rule must work both ways” (215, p. 74). Logically it would seem at first that it was a poor rule which did not work both ways. Further consideration will show, I believe, that there has been a confusion of feeble-mindedness with tested deficiency. If all the feeble-minded tested deficient intellectually then the tested level should determine whether or not they were feeble-minded. This, however, is not a correct psychological description of the facts. I prefer, therefore, to allow for those in a defined narrow range of weak intellects to be classed as deficient provided their weakness also manifests itself pronouncedly in the conative sphere.

The principle that all mental deficients need not show the same low degree of intellectual ability is clearly recognized in perhaps the most important legal enactment on deficiency which has been passed in recent years, the British Mental Deficiency Act of 1913. It states regarding “moral imbeciles” that they are persons “who from an early age display some permanent mental defect coupled with strong vicious or criminal propensities on which punishment has had little or no deterrent effect.” It specifically distinguishes them from the group of feeble-minded which require guardianship because of inability to care for themselves.

[3]. In Great Britain the term is restricted to those above the imbecile group.

CHAPTER III. THE PERCENTAGE DEFINITION OF INTELLECTUAL DEFICIENCY

A. The Definition.

In order to direct attention to the quantitative description of intellectual deficiency which is here proposed, let us state the percentage definition in its most general form. Individuals whose mental development tests in the lowest X per cent. of the population are PRESUMABLY INTELLECTUALLY DEFICIENT, unless their deficiency is caused by removable handicaps. Above these is a group of Y per cent. within which the diagnosis of intellectual deficiency is uncertain on the basis of our present tests. The size of the presumably deficient X group is to be determined by the number of intellectually weak which society is at present justified in indefinitely isolating. The doubtfully deficient Y group should include all those who are so intellectually deficient as to be expected to need assistance indefinitely. The feeble-minded, or MENTALLY DEFICIENT, are those who require social care indefinitely because of deficiency in mental development. They include the X group, that portion of the doubtful Y group which is found to require isolation, guardianship or social assistance, and any others not detected by the tests but requiring prolonged social care on account of their failure to develop mentally. Under the principle which we stated at the close of the last section the combination of Y ability and persistent serious delinquency brings the case within the group presumed to be feeble-minded.

Besides the greater definiteness and significance of such a definition of intellectual deficiency, it affords the simplest practical criterion for determining the borderline of passable intellects with a scale of mental tests. A detailed comparison of the percentage plan with other forms of quantitative definition will be found in Part Two. We may note here, however, that it guards against a number of the absurdities of current descriptions of the borderline with measuring scales. It is a criterion which may be consistently applied to the borderline of both the immature and the mature. It may be adapted with comparative ease to any system of tests. It aids in comparing the frequency of intellectual deficiency among different groups, for example, among different types of delinquents, regardless of whether the investigators have used the same series of tests, provided only that each series has been standardized for similar random groups.

Any form of quantitative definition, on the other hand, involves certain assumptions which must be defended before it can claim to be of advantage for practical purposes.

B. The Assumptions of a Quantitative Definition.

(a) Deficiency is a difference in degree not in kind.

Fortunately the tendency to describe the feeble-minded person as if he were a different species from the normal has been definitely attacked by two noteworthy researches, that of Norsworthy ([159]) and that of Pearson and Jaederholm ([164]) ([167]). In these two investigations mentally deficient children either in special classes or in institutions have been compared with groups of normal children from the same localities on the basis of objective tests. The results are uniformly supported by numerous other studies of deficient and normal groups with the Binet and other tests. The conclusion is, therefore, thoroughly established that there is no break in the continuity of mental ability. It grades off gradually from average ability, and continually fewer and fewer individuals are to be found at each lower degree of ability. The borderline of deficiency will, therefore, not be a mental condition which clearly separates different kinds of ability, but a limiting degree of capacity to be decided upon by social policy in attempting to care for those who most need social guardianship. Since ability changes gradually in degree it is necessary to indicate a doubtful border region of degrees of ability on which expert judgment must supplement the test diagnosis. Below the doubtful region the diagnosis is clearly supported by objective test criteria, so that the only question to raise is whether the condition is caused by removable handicaps. The percentage definition thus strictly conforms to the best objective studies of mental deficiency in treating deficiency as a difference in degree.

It should, perhaps, be said that this view is in direct conflict with the opinion that mental deficiency is accounted for as a Mendelian simple unit character. The opposing view has been advocated by Davenport (95, p. 310) and others in the publications of the Eugenics Record Office, and accepted by Goddard (112, p. 556). It has been so fully answered by Pearson ([164]) and Heron of the Galton Laboratory ([127]) and by Thorndike ([198]) that there is no occasion to take up the question in detail. We seem to be reaching an understanding so far as our present problem is concerned. If the explanation of the inheritance of mental ability is through Mendelian characters, nevertheless intellectual ability is the result of such a complex combination of units that it may best be thought of in connection with the unimodal distribution of ability adopted in this study. No random measurement of mental ability has ever shown any other form of distribution.

The attempt has also been made by Schmidt ([179]) to find qualitative differences between normal and feeble-minded children by means of tests, and by Louise and George Ordahl ([162]) to find qualitative differences between levels of intelligence among feeble-minded children. While these studies are very suggestive in pointing out the tests which most clearly indicate differences between individuals, they seem to me to fall far short of showing that the qualitative distinctions are anything more than larger quantitative distinctions. It is not clear that the authors intended them to mean anything more than this, so these studies do not seem to conflict seriously with our assumption that intellectual ability grades off gradually and uninterruptedly from medium ability to that of the lowest idiot.

(b) As to the variation in the frequency of deficiency at different ages.

A quantitative definition of intellectual deficiency would certainly be much simpler if it could be assumed that the percentage of deficients at each age is practically constant during the time when a diagnosis of deficiency is most important, say from 5 to 25 years. Otherwise the objection might be raised that it is impracticable to determine different percentages for each year of immaturity or to formulate our borderlines of ability for a particular age. When the general instinctive origin of intellectual deficiency is considered along with the incurability of the condition, we seem to be theoretically justified in assuming that the variation will be slight from one year of life to the next. This assumption is tacitly made by all those who use Stern's quantitative description of deficiency in terms of the mental quotient. On the other hand, there is a feeling among some of the investigators that there is a sudden influx of feeble-minded at particular ages and this position should be examined. Probably more important than this possibility of increase is the question of a decrease in frequency with age on account of the excessive death rate among the deficients.

It is a natural supposition that there is a sudden increase in the proportion of feeble-minded at adolescence. On account of the increased rate of growth at this period we might expect to find greater instability for a few years. It may well be that there is a rather sudden influx of the unstable type of feeble-mindedness at this period. Such an increase may occur without being detected by a series of brief intellectual tests such as the Binet scale. It would be of the conative type of feeble-mindedness that cannot at present be diagnosed by objective tests, the type that requires diagnosis by expert opinion. It is to be noted, however, that Binet, who paid much attention to the unstable type, says: “Since the ill-balanced are so numerous at ten years of age, and even at eight, we conclude that in many cases the mental instability is not the result of the perturbation which precedes puberty. This physiological explanation is not of such general application as is sometimes supposed” (77, p. 18).

Only when an emotional disturbance is so great as to be detectable by mental tests will this influx need to be taken into consideration in stating the borderline for objective tests. The evidence that few cases of feeble-mindedness are not detectable until after ten years of age is all the other way. With the Stanford measuring scale, Terman and his co-workers did not even find a noticeable increase in the variability of the groups at the ages of adolescence (57, p. 555). It is to be remembered also that we are not concerned here with mere instability which corrects itself with more maturity, such as has been described by Bronner among delinquents. This does not, of course, amount to an incurable conative deficiency and is not classified under feeble-mindedness.

Goddard has suggested that possibly the moral imbecile group comes into our class of feeble-minded suddenly with a common arrest of development at about the stage reached by the nine-year-old. He notes that “of the twenty-three cases of this sort picked out for us (at Vineland) by the head of the school department, fifteen are in the nine-year-old group, five in the ten-year-old, two in the eleven, and one in the twelve” ([113]). He regards this evidence, however, as meager and only suggestive. Doll has given evidence of late appearance of retardation in rare cases (100 and 99).

It is to be noted that if a sudden change is found in the percentage of children falling below a certain test standard it is perhaps more likely to mean that there is a change in the difficulty of the tests at that point. For example our Table V shows 1.3% of the nine-year-olds test two or more years retarded, while 18.9% of the ten-year-olds are retarded two years or more. This presumably indicates a change in the relative difficulty of the tests for VII and VIII rather than a change in the frequency of retardation at ages nine and ten. When we turn to Goddard's norms for VII and VIII we find that 81% of the seven-year-old children pass the norm for VII while only 56% of the eight-year-old children pass the norm for VIII.

The Jaederholm data ([167]) obtained by applying the Binet tests to pupils in the regular school classes and in special classes for the retarded may suggest a possible influx of intellectual deficiency at about 12 years of age or else “more mental stagnation in the intellectually defective” at this life-age and after. If one were to define intellectual deficiency in terms of the standard deviation of the regular school children, this data suggests that there is a marked increase in the number of children sent to the special classes at 12 years of age who are -4 S. D. or lower. Roughly speaking it amounts to 36 children at 12 years of age, 36 at 13, and 21 at 14, as compared with 11 at 11 years and 13 at 10 years. On the other hand, this may as well mean that intellectual deficiency becomes greater in degree rather than in frequency at these ages. The latter interpretation is adopted by Pearson for the Jaederholm data, so that it is perhaps not necessary to consider this evidence further. On the average the pupils in the special classes fall about .3 S. D. months further behind regular school children with each added year of life from 5 to 14 inclusive. A third possible interpretation of the greater number showing the degree of deficiency measured by -4 S. D. with the older ages should be mentioned. It is possible that 1 S. D. has not the same significance for 5-year-olds as for 12-year-olds. The distribution of abilities at succeeding ages may be progressively more and more skewed in the direction of deficiency. We shall return to this point in Part Two as showing the advantage of the percentage definition over a definition in terms of the deviation. In connection with the Jaederholm data on special classes one should also consider the fact that younger children are not as likely to be detected by the teachers and sent to the special classes. It is possible also that the difference in difficulty of the tests for different age groups is somewhat obscured by using a year of excess or deficiency as a constant unit as Pearson has in treating this data. The bearing of this difference in difficulty was pointed out above for Goddard's data.

The investigations by Pearson of children in the regular school classes indicate that there is no important shift with maturity in the frequency of those with different degrees of ability, when the ability is measured either in terms of years of excess or deficiency with the Jaederholm form of the Binet scale or in terms of estimates of ability relative to children of the same age (166 and 167). In both these studies the correlation of ability with age was shown to be almost zero. For tested ability for 261 school children “r” was .0105, P. E. .0417; with the estimated ability, the correlation ratios were for 2389 boys, .054, P. E. .014; for 2249 girls, .081, P. E. .014. Until we have better data this is certainly the most authoritative quantitative answer to the question of the shift with age in the frequency of the same relative degree of mental capacity.

The best method of empirically settling this question of the early appearance and constancy of deficiency would be to test the same group of children again after they had reached maturity and find out how many of those who tested in the lowest X per cent. still remained in the same relative position. This is, of course, not possible at present, but it certainly should be done before we are dogmatic as to the permanent isolation of the lowest X percentage at any age. The nearest approach to this sort of evidence is Goddard's three annual testings of a group of 346 feeble-minded children with the Binet scale (117, p. 121-131). Among these 109 showed no variation, 123 gained or lost 0.1 or 0.2 year, 18 lost 0.3 or more, and only 96 gained 0.3 or more of a year. With so small a change in absolute tested ability the probability of a change in position relative to normal children seems to be slight. Only one of the 76 who had tested in the idiot group gained as much as a half year in tested age in three years.

It is not possible to settle this question of the constancy of the percentage of intellectual deficiency from one life-age to the next by considering the frequency of different ages of children among those who are sent to special classes for retarded pupils. This is evident from the fact that these classes contain a considerable proportion of those who are feeble mentally mainly because of conative disturbances. These would not be detected by our present tests and would not be classed as intellectually deficient. In the second place the pupils for the special classes are usually selected mainly on the advice of their teachers, who cannot, of course, without tests select those who are intellectually deficient except by trying them for a number of years in the regular school classes. This means that a smaller percentage of pupils in the special classes at the younger ages is to be expected.

The figures of the U.S. Census as to the ages of inmates of the institutions for feeble-minded are also of little significance in connection with the question of the variation from age to age. That the number of inmates at the different ages is affected most largely by the pressure of necessity for shifting the care from their homes to the institution is shown by the fact that three-fourths of the admissions are of persons over 10 years of age. It is also indicated by the fact that for the period from 15 to 19 the males are over 20% more frequent than females, while from 30-34 the females are nearly 20% more frequent. Considering those ages most frequently represented in the institutions, 10-24 years, the average variation for the three five-year periods in the percentage of the population of the corresponding ages who are in these institutions is only 0.01%. The middle five-year period has the most, but even if there were a cumulation of feeble-mindedness with age, which is not shown, we would anticipate a change of not more than 0.05% for these 15 years. This would be clearly negligible in considering the general problem.

That little allowance for the variation from age to age need be made for the number of cases not discoverable at the beginning of school life is further indicated by report of the Minnesota State School for Feeble-Minded. It shows that in only 247 out of its 3040 admissions was the mental deficiency known to commence after six years of age ([154]). If the number of feeble-minded who should be isolated were found to increase after school age less than one in 10,000 of the population, as this suggests, it would surely be better to neglect this variation from age to age than to emphasize it in dealing with the problem of objective diagnosis and social welfare.

How rare is the onset of feeble-mindedness after five years of age is also shown by the frequency of hereditary causes. In his study of the 300 families represented at Vineland, Goddard places only 19% in his “accidental” group and 2.6% in the group for which the causes are unassigned. The rest are either in the hereditary group, probably hereditary, or with neurotic heredity. Half of the cases in the “accidental” group are due to meningitis. His histories show that only 9 of the “accidental” and unassigned groups were unknown at 5 years of age. This is only 3% of his total feeble-minded group. To these might be added, perhaps, a few from the hereditary groups who did not show their feeble-mindedness at so early an age, but so far as I can judge these would not be of the intellectually deficient type that would be detectable by the Binet scale at any age. They would test high enough intellectually to pass socially and require expert diagnosis to be classed as feeble-minded.

Certain diseases, epilepsy and meningitis, are undoubtedly causes of feeble-mindedness. The evidence, however, seems to be that they are so rare compared with the mass of mental deficiency that after 5 years they may well be offset by the excessive death rate among the feeble-minded. That recoveries from feeble-mindedness are insignificant is generally agreed. Among the 20,000 in institutions in 1910 only 55 were returned to the custody of themselves. This is further evidence of the fundamental, if not congenital, nature of the deficiency.

While the evidence submitted above makes it seem fair to assume that the increase in the frequency of a certain degree of intellectual deficiency with age is probably negligible, it is not clear that the decrease with age in the proportion of feeble-minded caused by an excessive death rate may be neglected even for the test ages 5 to 25. By searching the literature it has been possible to assemble the records for nearly 3500 deaths among the feeble-minded in institutions in this country and Great Britain distributed by ages in ten-year periods. This evidence is presented in Table I. The number of cases under five years of age living in the institutions is so small that the deaths under five years are certainly misleading. They have, therefore, been omitted from the table and the distribution calculated for those five years or over (123, 154, 204, 205). Comparison is made with a similar distribution of the total deaths for a period of five years from 1901 to 1904, inclusive, within the area of the United States in which deaths are registered, compiled from the special mortality report of the Bureau of the Census ([206]). This registration area has a population of about 32,000,000. The general agreement of the distribution of deaths among the four different groups of institutional inmates seems to make it reasonable to assume that the United States group of institutional deaths for the year 1910 is a conservative description of excessive death frequency at the early ages among the feeble-minded in institutions.

Table I. Age Distribution of Deaths in the General Population and Among Feeble-Minded in Institutions.

Table II. Mortality of Institutional Deficients in the United States Compared with the General Population, Showing its Possible Effect on the Frequency of Deficiency at Different Ages.

Fig. 1. Mortality among Feeble-Minded in Institutions Compared With the General Population

A comparison of the death rates of the feeble-minded and the general population at different ages is of prime importance in connection with all attempts at quantitative descriptions of deficiency. Heretofore this has been completely neglected. Fig. 1 and Table II have been prepared to provide a roughly adequate estimate, on the basis of the above data for the United States, as to the survival of 1000 institutional cases of feeble-minded 5 years of age for successive age periods compared with 1000 people in the general population. In constructing this table it was necessary to assume, since the facts were not given, that the age distribution in the registration area of the general population was the same as for the United States as a whole (census of 1910) and that the number of feeble-minded in the institutions at the various age periods was equal to the number enumerated on the first of January plus the admissions during the year 1910, disregarding the number discharged since they are not distributed by ages. The average annual death rate among the institutional cases of feeble-minded 5 years of age and over in the United States in 1910 was 35.19 per thousand, while the corresponding death rate in the general population of the registration area for the five years 1901-1904 inclusive was 13.56. Assuming that the death rates are uniform within the five-year periods, the decline in the proportion of institutional feeble-minded from 5-25 years of age as the result of excessive mortality is indicated by the last line in Table II, after allowing for the mortality in the general population. That this effect of excessive mortality upon the percentage of feeble-minded cannot be neglected between 5 and 25 years of age is apparent unless the mortality among institutional cases is much greater than it is among the deficient generally. As the figures stand the proportion of feeble-minded would be reduced nearly one-half between ages 5 and 25. Only a small part of this reduction probably would be compensated for by new cases developing from accident or disease. On the other hand there is little doubt that the institutions contain an excessive proportion of low grade cases among whom the mortality is much greater. The mortality among institutional cases is, therefore, probably not typical of that among the feeble-minded generally. Nevertheless it is so great that any quantitative definition of deficiency which neglects it entirely is open to serious objection. We shall, therefore, keep this variation in mind in connection with the discussion in the next chapter of the percentage which is deficient, and in the adaptation of the definition to a measuring scale. It is clear that the percentage should be so chosen as to allow best for the possible large effect of excessive mortality among the deficients. Finally, it should be said that the percentage definition of feeble-mindedness might be modified to meet a varying percentage from age to age should that ever become desirable.

(c) As to the number of deficients not detected by tests.

If most of the feeble-minded for whom society should provide were of the type which is only conative and not detectable by our present objective tests, a quantitative definition would be abortive. We must, therefore, study our assumption that it is worth while to direct our attention to those who are intellectually deficient. We shall attempt to discover how frequent are the primarily conative types.

Before examining the quantitative evidence we may note that it is in conformity with two prominent recent tendencies in psychology to subordinate specialized abilities, as compared with abilities which function commonly in many situations. The first of these tendencies is represented by the fundamental researches of Hart and Spearman ([123]) ([185]). This is not the place to set forth the technical work on which their conclusions are based. It may be said, however, that, with 17 different psychological tests, they were unable to discover any important specific mental weakness which distinguished adults who were suffering with any one of various mental abnormalities, including imbecility, manic-depressive insanity, dementia praecox, paranoia, and general paralysis of the insane. This may have been the fault of the tests, but it seems to be more likely that the fault lies in the custom of emphasizing special abilities and disabilities, at least from the point of view of tested capacities. On the other hand, all of these mental abnormalities showed a weakness in general intellectual ability. This is true whether this general ability be regarded, as it is by Hart and Spearman, as due to a general fund of brain energy, or whether general ability be taken to refer to the common recurrence of many specific abilities in much of our mental life. Its significance for this study is that a series of varied tests, such as that of Binet, may be expected to give a good estimate of general ability, and its failure to disclose specific disabilities is thus less important.

The second influence in psychology tending to emphasize average tested ability is the establishment of the biological conception of the mind which recognizes the mutual interdependence of the mental processes, organically united through the activity of the brain. So long as intellectual, emotional and volitional processes are all mutually dependent, a disturbance of one aspect of mental life is bound to affect the others. In considering the mutual dependence of the mental processes, it is important to weigh carefully the striking examples which Bronner[^[4]] has brought together, illustrating special abilities and disabilities. She has made an admirable start toward a differential diagnosis of special defects in number work, language ability and other mental activities. The degree of special deficiency which results in social failure could be placed upon an objective basis, but the rarity of special deficiencies as compared with general deficiency will make this a slow task. In the meantime we may rely upon the mutual dependence of the organic processes as a point of view which emphasizes the common spread of deficiency to many activities. Knowledge of a single case of specific disability is sufficient to make us recognize that such cases do occur. On account of the rarity of those cases and the absence of objective criteria, it seems necessary to leave the further differentiation to the future, considering here only those cases which may be grouped together as conative, as contrasted with those detected by our general intellectual tests.

Whether the group of primarily conative cases is of any considerable size can be only very roughly estimated at present, since the diagnosis of such cases of feeble-mindedness rests at present almost exclusively on the subjective opinion of the examiner. Before their diagnosis is put upon an objective basis we must have a different form of test directed at such traits of will as initiative, perseverance, stability and self-control. These probably center on the mental side around the instinctive emotional background of interest and the passions, while, on the physical side, they raise the question whether the subject's energy is adequate to endure the strain of competition or whether it shows itself only in sudden bursts.

If the diagnosis of conative cases could be determined objectively, it is possible that most forms of social unfitness would be found highly correlated with intellectual deficiency. On the other hand, when the diagnosis of unfitness for school or social life depends merely upon the opinion of experts or teachers, the inaccuracy of the diagnosis may show a wide discrepancy between the so-called conative and intellectual types of deficiency. Binet, on the basis of his acquaintance with the pupils in special classes, suggested that the number of unstable children is probably equal to the number of those who are intellectually unsuited for the ordinary schools or institutions ([77]). Since he then places the total number of the two classes at four or five per cent., it is apparent that he is discussing a higher type of ability than is usually included under the term feeble-minded. We can get somewhat better evidence on this question by studying the results of Binet tests applied to children cared for in special classes or in institutions for the feeble-minded. Chotzen (90) presents a table of 280 children in the Hilfsschule in Breslau, only 201 of whom, however, he himself diagnosed as feeble-minded, i. e., debile or lower. Of these only 51 were intellectually deficient as indicated by the Binet tests when we include the doubtful cases according to the criteria we have adopted in this study. If we suppose that, in addition to those in the special classes, there would be one intellectually deficient child in an institution for feeble-minded for every child testing deficient, we would then guess that only 40% of the feeble-minded children in Breslau were intellectually deficient. This sort of estimate seems to agree with Binet's belief that half of the children requiring special care, at least during school ages, are cases which are primarily conative.

Pearson has approached the same problem in another way ([164]) ([167]). He has used the results of the psychological tests applied by Norsworthy to children in New York in special classes and institutions for feeble-minded compared with those in the regular school classes, and the results of Jaederholm obtained with the Binet tests applied to 301 children in Stockholm in the special classes compared with 261 others selected from the regular classes. He found that “70.5% of normal children fall into the range of intelligence of the so-called mentally defective; and 60.5% of so-called mentally defective children have an intelligence comparable with that of some normal children” (167, p. 23). On the statistical assumption that those in the normal classes would distribute according to the Gaussian normal probability curve he estimates that, with the Binet tests, among those in the special classes “10% to 20%, or those from 4 to 4.5 years and beyond of mental defect, could not be matched at all from 27,000 children” (164, p. 46). Another 20 to 30% could be intellectually matched by those in the regular classes having from 3 to 4.5 years of mental deficiency, but they would be matched very rarely. On the assumption that 1% of the children were feeble-minded, not more than about two children in a thousand of this regular school population would be expected to be 3 or more years retarded and thus overlap those of like deficiency in the special classes (167, p. 30). Considering the results of Norsworthy's study he says on similar assumptions: “It seems, therefore, that a carefully planned psychological test, while not sufficing to differentiate 50 to 60% of the mentally defective from the normal child, would suffice to differentiate 40 to 50%” (164, p. 35). Again we come back to the estimate that psychological tests may well be expected to select nearly half of the children at present found in special classes for retarded pupils. Moreover, a considerable part of the overlapping of intellectual deficiency in the regular classes with that in the special classes which he found may be accounted for by the inadequate methods of selection of pupils for the special classes by teachers or examiners who have used no objective tests. Some who were left in the regular classes should undoubtedly have been transferred to special classes and vice versa. There seems to be nothing to indicate that less than half of those properly sent to special classes would be of clear or doubtful intellectual deficiency. If the tests served to select even a smaller proportion of those assigned to special instruction, the “school inefficients” as Pearson calls them, their value as an aid to diagnosis would be demonstrated.

Among groups of delinquents, where we would expect the purely conative cases to be more common, we find that a careful diagnosis of feeble-mindedness on the basis of test data, medical examination and case history indicates that conative cases without serious intellectual deficiency are much rarer than intellectually deficient delinquents. At least this is the evidence of one study where such information is available. Kohs at the Chicago House of Correction found among 219 cases over 16 years of age, which he diagnosed as feeble-minded, only 28 tested XI and there were only 52 who did not test either presumably deficient or uncertain intellectually according to our criterion. Another bit of evidence is that collected at the Clearing House for Mental Defectives in connection with the New York Post-Graduate School of Medicine, where 200 consecutive cases (108 males) were examined by Miss Hinckley. Her graphs show that only 15% tested X or above with the Binet revised scale, i. e., above those presumably deficient in intellect. The cases were from 13 to 42 years of age. The clearing house provides an opportunity for social workers to have suspected deficients examined and the few cases over X seems to indicate that the purely conative type is not very commonly met with among the social workers.

When we turn to the institutions for the feeble-minded we find that they are today caring for few solely conative cases. Although I can find no tables which give both the life ages and mental ages of the individual inmates, we can at least be sure that few test so high as X, or above with the Binet scale. This means that only a few have as yet reached the threshold for passable adult intellects, which should be attained by 15 years of age. At the Minnesota state institution for the feeble-minded in Faribault among 1266 inmates, excluding epileptics, 41 tested X; 28, XI; 12, XII; and 8, XIII, a total of 7% ([154]). At Vineland, N. J., Goddard reported among 382 inmates, 14 tested X; 5, XI; and 7, XII, about 7%. Some of the children who were under 15 in life-age might later develop above the limit for intellectual deficiency. Of the 1266 at the Minnesota institution, however, 508 were 15 or over at the time of their admission, so that at least 82% of the 508 were clearly intellectually deficient. Eight per cent. more tested X and were in the doubtful group in intellectual ability according to the criteria we have adopted. This suggests that not more than about 10% of those who are at present isolated in institutions are there for feebleness of will alone. It seems to confirm our presumption that the intellectually deficient discovered by tests form the great majority of the social deficients who need prolonged care or assistance.

(d) Allowance may be made for variability.

The quantitative definition of intellectual deficiency must be made with careful allowance for irregularities among different mental processes, among different individuals, and among different groups. Theoretically it is possible to place the borderline so low that a case with that degree of deficiency and without removable handicaps would be clearly feeble-minded. The chance that the diagnosis would be mistaken could be reduced to any minimum desired. Above this a wider region of doubtful deficiency could then be stated in similar form. This is the plan that we suggest in attempting the percentage definition. Practically, however, the plan assumes that a suitable allowance can actually be made for these variations and raises a number of problems as to variability which should be considered. Four of these sources of variation are discussed below: (1) the variation due to a limited sample of individuals measured, (2) the variation among different communities, (3) the variations arising from sex, race and social differences, (4) the variation of the same individual from one mental process to another. We do not have the problem of neglecting these variations, but of adequately allowing for them both in the percentage of presumably deficient and in the doubtful region.

(1) Variation among Samples of Individuals Measured. The error introduced by the fact that measurements are made on a limited rather than an unlimited number of individuals, in establishing the standards with a system of tests, can be taken care of statistically fairly well by applying the theory of probability as to the error of a percentage in a single sample. The range of the error can then be indicated on the measurement scale. This supposes, however, that each sample to be measured is taken from a random group and not from a selected group. Allowance for this error of sampling is therefore complicated by the fact that the usual test data have been obtained from groups of school children, even when there has been no further selection within the school group. Data on school children are certainly reliable only within the years of compulsory school attendance. Ordinarily in this country, they are not reliable for children of 14 years of age or over. Moreover, the point of the scale which is reached by the lowest X percentage of school pupils will exclude a slightly larger percentage of all children of corresponding ages, since the idiots and some imbeciles are not sent to the ordinary schools. This slight discrepancy should be kept in mind. The problem of avoiding selected samples among adults is still more difficult; but we found that it was possible in one community at least to measure all the 15-year-olds in the lowest X percentage in certain districts, as we shall note later. By this age, mental processes are probably very much like those of adults, except for the amount of information and practise.

(2) Variation among Different Communities. Under any conception of deficiency it is clear that there are relatively more deficients in some communities than others. The percentage should, of course, not be determined for a small community such as a city or county, but for a state or a nation in order to avoid the difficulty of the difference between communities. It would not interfere with the plan for isolating the lowest X percentage of a state even if that meant isolating 10% in one small community and none in another. Indeed, it might be expected to do just that, when one considers the accumulation of deficiency in certain settlements such as Key has shown (131, p. 63). The data on which the borderline with a measuring scale would be established should, of course, not be obtained from communities known to be unusual in respect to the frequency of deficiency.

Since social failure is our final criterion for judging deficiency, we must further consider that it is easier for a person to survive in one environment than in another: in the country, for example, than in the city. This sort of problem has led to considerable confusion. Goddard remarks: “In consequence of this it happens that a man may be intelligent in one environment and unintelligent in another. It is this point which Binet has illustrated by saying 'A French peasant may be normal in a rural community but feeble-minded in Paris.'” (117, p. 573.) Goddard then goes on to suppose that a delinquent with the intelligence of a sixteen year old may be “defective” because he happens “to have got into an environment that requires a twenty-year-old intelligence.” The suggestion that a criminal might be excused on the ground of deficiency because he happened to fall among bad companions is a reductio ad absurdum. Clearly environment must be defined as ordinary environment, available environment or by some similar concept, or else the definition of deficiency loses all significance. In another place Goddard more properly suggests that it would be well to “draw one line at that point below which a person of that intelligence is not desirable or useful in any environment” (117, p. 3).

So long as the care of the feeble-minded is a state problem the percentage of passable intellects would apparently be determined for the available environment in that state. The problem of social care cannot mean that the state should care for college men because they cannot survive among college men or in the station of life into which they may have been born. So long as there are environments within the community where they can survive it is a problem of shifting them in their social habitat, not a problem for social care. The same is true for the low grades of intellect. It is not likely, however, that any portion of the community could absorb many more of the low degree intellects. For the problem of social care for the feeble-minded, the question: What environment will allow this individual to survive? becomes the question: Can he survive in any available environment in his community? It would seem very hazardous to suppose that the different opportunities for survival afforded by different localities in a state would be large enough to care for more than the group of doubtful cases which should be allowed for in a quantitative description of the border region.

(3) The Variation with Sex, Race, and Social Position has been carefully called to attention by Yerkes and Bridges in their studies with the Binet Point Scale (225, Chap. V and VI). It may very well be that not as high ability should be expected of certain groups as of others; as a matter of moral obligation, they are not as responsible for their conduct or their attainments. On the other hand this does not directly affect the question, what lowest percentage of intellects cannot get along in society? When that percentage is determined for the environment available in the community all those who fall within it might even turn out to be of one sex or of one nationality or of one social position, without affecting the question whether they should be cared for by society, or what grade of intellect is not socially passable? Temporary social handicaps, such as lack of familiarity with the language, lack of training, etc., must, of course, be allowed for so far as they affect the individual's test record. Whether the difference of 5% to 10% in the score of pupils born to non-English-speaking families compared to their companions' (225, p. 66) is due to the temporary handicap of language or to a permanent difference is, however, just the problem which the Yerkes and Bridges study does not answer. The fact that the difference is even greater for older children suggests that it may indicate an inborn difference between the groups compared.

A diagnosis of deficiency should not be made until the examiner is able to estimate whether the removal of training or health handicaps would bring the individual above the borderline. So far as known temporary handicaps affect the standard of the test results with groups they should, of course, also be taken into account. On the other hand, it is clear that the borderline which predicts social failure should not be shifted to allow for differences in permanent handicaps whether those be of race, sex or social position.

(4) The Variation among Different Mental Processes. With our present knowledge the most difficult variation for which we must make allowance at the borderline is the variation from one trait or process to another in the same individual. One phase of it was discussed above under “c.” The investigation of Norsworthy throws light on this question. Summarizing her tests she says: “Among idiots there is not an equal lack of mental capacity in all directions. There is something of the same lack of correlation among the traits measured in the case of idiots as there is with ordinary people” (159, p. 68). Again: “The idiots are nearest the central tendency for children in general in the measurements of mental traits which are chiefly tests of maturity, and farther and farther away as measurements are made which are tests of ability to deal with abstract data. They are two and a half times as far from the median for children in general in tests like the genus-species test as they are in tests like the A test or the perception of weight.” Weidensall ([60]) and Pyle ([46]) also compare delinquent and normal individuals for different tests, showing a variation with the sort of mental activity compared.

While Norsworthy thus presents evidence of certain specializations of deficiency, she notes, however, that perhaps feeble-mindedness is more typically general than specific and that general deficiency is more important to consider than specific. Even with that test with which her group of retarded and feeble-minded children did best, only 28% of them passed the point which would be excelled by 75% of the children in general. In their worst test only 1% passed this point. It is also to be noticed that those tests in which they most nearly approached ordinary children are for just those simple processes which would be least likely to be of use in the struggle for social existence. As a whole, therefore, there is nothing in her results which shows that any appreciable number of children who were deficient in the average of tested abilities, would have good enough special ability along a few lines to make them socially passable. Indeed, for all that we know at present, the borderline for passable ability in each of our various mental processes might vary quite as much as Norsworthy found, without this variation affecting a prediction of failure based upon the average of a series of tests.

On account of the great attention that has been paid to individual differences in recent years, on account of their importance for diagnosis, for determining the causes of deficiency, and for planning for the training of deficients, we have come almost to the point where we forget the significance of the average as the most common condition with which we have to deal. The lack of complete correlation between abilities of an individual does not make us hesitate to use the concept of his average ability; it should not make us neglect or misunderstand the significance of the position of an individual testing low down on the scale. For the problem of social care the borderline position on a scale is immensely more important than higher ability. It seems advisable, therefore, to define this borderline ability with some suitable allowance for variability in mental processes. It is far safer to judge an individual's chance of survival by his average or general tested ability than by the little knowledge that is as yet available regarding special abilities.

[4]. Augusta F. Bronner. The Psychology of Special Abilities and Disabilities. Boston, 1917, pp. vii, 269.

CHAPTER IV. WHAT PERCENTAGE IS FEEBLE-MINDED

A. Kinds of Social Care Contemplated

At first it seems like a hopeless task to try to bring harmony out of the confused estimates of the proportion of the feeble-minded in modern society. Authoritative estimates by commissions or by recognized experts range from less than 0.2% to 5.0% that is, from 2 to 50 per thousand. Further study of these estimates shows that they reflect not so much a difference in expert opinion about the same problem as differences in the problems which were considered in making the estimates. As soon as we compare only those estimates that have been made to answer the question, what percentage of low grade minds should be provided with a certain form of social care? it is rather surprising how much less the discrepancy becomes. An analysis of important estimates will therefore be undertaken in order to try to discover some of the sources of disagreement.

The most significant thing about an estimate is that the estimator is thinking of providing for his group of deficients in a special way. This is the purpose of the estimates. Three important groups of the mentally deficient now demand attention. They are: (1) The group which, for moral and eugenic reasons, society is justified in isolating for life or an indefinite period. (2) The group which needs special simple industrial training in order to get along with social assistance without isolation. These deficients may be cared for in their home towns by special schools, public guardians, and after-care committees. (3) The group which needs special school assistance, but is socially passable after leaving school. These individuals are incapable of competing in school with their fellows, but they are able to get along in the simplest employments without social assistance. We may designate these three groups as those needing (1) social isolation, (2) social assistance, and (3) only school assistance. The largest estimates of feeble-mindedness, it will be found, include the third group, while the smallest intend to include only the first group. The first and second groups are clearly below the limit of feeble-mindedness designated by the verbal definition of the British Commission. They are socially unfit. The language of that definition is ambiguous enough to include the third group, but the plan of the Commission, judged by its consideration of the number to be sent to special schools, would regard only the first two classes as feeble-minded. Following this common conception I have regarded those in the third group as above the feeble-minded. It will help to find harmony among the estimates if we estimate separately those mentally deficient enough to need social isolation, social assistance, and only school assistance. This discrimination of the retarded by the kind of social care needed should also make the social definition more useful.

B. Estimates of the School Population Versus the General Population

Before we consider the percentage estimates in detail for these different forms of social care, let us note the effect on them of two other considerations. The first of these is the discrepancy between estimates of the proportion of feeble-minded among school children and estimates as to the proportion in the general population. Since feeble-mindedness is regarded as a permanent arrest of mental development occurring at an early age and usually due to hereditary causes, it is plain that a school child who is feeble-minded would be expected to remain so for life. Nevertheless we find that estimates of 0.3% of the general population are accompanied by estimates of 1.0% or 2.0% of the school population as feeble-minded. I have not been able to find any careful attempt to account for these discrepancies. The excessive mortality among the feeble-minded is hardly adequate to explain so great a difference.

It is interesting to note some of these comparisons. Goddard, for example, considers it conservative to estimate that 2% of the school population is “feeble-minded” (112, p. 6). In the same publication he says: “There are between 300,000 and 400,000 feeble-minded persons in the United States” (p. 582). Since the elementary school enrollment is about 20,000,000 ([208]), the feeble-minded school children alone on his first estimate would account for 400,000 feeble-minded in the United States without allowing for any feeble-minded outside of the ages in the elementary school.

The report of the British Royal Commission, published in 1908, forms the starting point for many of the estimates made today. The commission added together the number of school children which were thought to require special classes with the number of defectives found in institutions, prisons and almshouses, or reported by its medical investigators. The total gave 0.46% of the general population as “mentally defective persons,” not including certified lunatics. From this amount should be deducted .06% who were insane but had not been certified as such, leaving 0.4% mentally deficient. This was not regarded by the Commission as an estimate, but was the number actually “enumerated by the medical investigators” in sixteen typical districts studied in England and Wales with a total population of 2,362,222 (83, VIII, p. 192). Turning to the school children we find that in the areas investigated there were 436,833 school children of whom 0.79% were found defective. Since this was an enumeration and not an estimate, the commission paid no attention to the discrepancy between 0.79% of the school children and 0.31% of the rest of the population. Tredgold, moreover, based his estimates of the frequency of the mental deficiency in England and Wales on the data of the Royal Commission without attempting to harmonize this discrepancy. This oversight has apparently been one source of the not uncommon difference between the estimates for school children and for the general population. One suspects that the fact that the elementary school population is about a fifth of the general population, has also mistakenly contributed to this error. The discrepancy of three to five times as large a frequency of deficiency among school children as in the general population certainly needs clearing up.

There is an escape from this dilemma which seems more reasonable than to attempt to account for the discrepancy by excessive mortality. When estimates are made concerning the school population the estimator is usually thinking of that group of feeble-minded which needs special school training and probably social assistance afterward. When estimates are made of the general population the estimator is likely to be thinking of that group which must be cared for permanently by society, mainly in institutions or colonies. For some time at least the state cannot be expected to undertake the indefinite care of all the deficients who should have, at once, simple industrial training, in special local schools or classes in order to survive, even with social assistance. This difference in the type of care contemplated seems most naturally to account for the discrepancy found with many writers, between their estimates for the school population and for the general population.

C. Desirable Versus Immediately Advisable Social Care

A second source of confusion arises when one investigator is thinking of the number of feeble-minded, the care of whom it is desirable that society should assume, and another is thinking of the feeble-minded, the care of whom it is advisable for society to assume at once. Considered in connection with a specific case the distinction is quite obvious. It is one thing to say that it would be desirable for the state to assume the indefinite care of a particular person, it is quite another thing to say that it would be advisable for the state to assume that care immediately, when one remembers the crowded condition of the institutions, the necessity of caring for the worst cases first, the possibility of the person being cared for by his own family or in a local school, the added public expense, the necessary neglect of other movements for social welfare if society assumes this expense, etc., etc.

When you magnify this problem in the mind of the estimator who is interested in the question of caring for the groups of feeble-minded, the result is that his estimates of the size of the groups are decidedly affected. For example, few would deny that the Site Commission of New York appointed to locate the colony for mental defectives, now known as the Letchworth Village, was emphasizing a program of permanent social care when it estimated the number of feeble-minded in New York. The Commission, “after taking into consideration the figures of the State and National census, and other data collected from institutions,” estimated that there were in New York state possibly 12,300 mentally defective persons (Editor's Note, 205, p. 84). This is less than 0.15% of the population and very low compared with most estimates.

The low estimates will generally be found to be influenced by considerations of public expense rather than the social unfitness of the lower group. Inasmuch as there are no sharp distinctions between different degrees of mental ability this consideration of public expense is perfectly proper. At the other extreme, however, are the eugenists who are convinced that it is desirable to isolate a large group at the lower range of ability. The member of the legislature will be concerned mainly with the question how much money will the public be willing to appropriate now for the care of these unfortunates. The eugenist will be thinking of an ideal rather far in the future towards which to work.

The diagnostician should take a conservative intermediate ground. He may leave to the court or other authorized tribunal to decide whether the public has the facilities available at present for caring for a particular weak-minded person, but he must decide whether expert scientific opinion at the present time will justify diagnosing this degree of deficiency as suitable for the special care provided for the feeble-minded. Whether it is advisable to care for the particular deficient at home, in a special local school, or in a state institution would be left to the legal authority to decide. Under present conditions, the diagnostician may possibly indicate whether the individual is deficient enough to justify social isolation, or merely to justify sending to a local elementary day school for deficients.

D. Percentages Suggested to Harmonize the Estimates

It is from the point of view of the diagnostician that we shall attempt to focus this question of the percentage of feeble-minded. We shall tentatively suggest limits as to the degrees of intellectual deficiency which we might be justified in regarding, under the present conditions of scientific knowledge as being low enough in intellectual capacity to justify particular forms of social care. Such estimates will be of value if they help to harmonize the conflicting opinions by bringing them into relation with the above analysis. We shall, therefore, compare the suggested percentages with a number of authoritative statements of the frequency of feeble-mindedness. By considering the differences in the nature of the estimations we may approach nearer to an understanding of the problem.

Since the percentages to be suggested are chosen from the point of view of diagnosis, they do not represent the number for which every community should immediately make financial provision. The expense is a local or a state question. It is so much affected by state conditions and by public policy that it probably must be determined in any state by a special commission. On the other hand, the laws already provide for caring for the feeble-minded in institutions or colonies and in special schools or classes, so that the estimates may help to guide diagnosticians who are called upon to decide whether a particular person might be rightfully regarded as deficient enough intellectually to justify committing him for permanent care to a state institution. In the present practise it is fairly clear that this distinction is made in the minds of different diagnosticians. It may ultimately be desirable that this differentiation between the types of social care be introduced into the law. Until then it will remain the duty of the court to determine what degree of social unfitness is intended by a particular law. The social concept of feeble-mindedness is just now undergoing a rapid evolution so that it would be impossible to predict how it may legally crystallize a generation hence.

To begin with the lowest group of the feeble-minded, we should consider those whom the state might be clearly justified in isolating indefinitely on the basis of their tested lack of intellectual capacity, the social isolation group. For purposes of comparison let us place this degree of intellectual ability as that possessed by the lowest 0.5% at fifteen years of age. Above these let us estimate a group of uncertain cases so far as isolation is concerned, but cases which the diagnostician would be justified in regarding as intellectually deficient enough to justify sending to special local schools for training the feeble-minded. After special training the majority of these cases might be expected to require social assistance indefinitely. They would form the social assistance group. Isolation would be justified for none of them on the basis of their test records alone. Those in this group who were persistent delinquents would, by that additional fact, fall into the lowest group so far as social care is concerned. Let us estimate this social assistance group tentatively as the next 1.0% at fifteen years of age.

These estimates have been made as at fifteen years of age since the effect of the excessive mortality especially among the isolation group is uncertain and may need to be allowed for in a discussion of the percentage deficient at different ages. If the mortality were as great as has been described among institutional cases in the previous chapter, a rough estimate of the percentage intellectually deficient in the general population places it at less than 0.5%. This estimate may be made by using the estimated deficiency at the median age of those under 15 years of age and at the median age of those 15 years of age and over. According to the age distribution of the 1910 census, there were 32% under 15 years with a median age of 6 years. At age six 0.67% would be presumed as low as 0.50% at 15 years. The older group (68% of the population) has a median age of 32 with a corresponding percentage in the isolation group at that age of 0.30%, after allowing for differences in mortality on the plan indicated in Table II. This rough estimate for the lowest group indicates that 0.42% of the general population would be of as low a degree of intellectual capacity as the lowest 0.5% at 15 years. Our plan presumes, therefore, that between 0.4% and 0.5% of the population are unable to pass their entire lives outside of institutions under ordinary conditions; i. e., make an honest living and live within the law even with social assistance and supervision.

The corresponding estimate for those requiring only social assistance would be between 0.8% and 1.0% of the general population above the lowest group. This might vary from approximately 1.34% at 6 years to 0.59% at 32, the median age for those over 14 years. Since the mortality is probably less among deficients not in institutions, as they average higher in ability, the changes in the percentages are probably extreme estimates. We should keep in mind, however, the possibility that with the excessive death rate the lowest 1.0% at 15 may mean an ability corresponding to the lowest 1.34% at 6 years and the lowest 0.60% at 32 years.

The next higher group in intellectual ability is so high as not to require social assistance outside of school. When we ask how large a per cent. we should be justified in placing in this group and separating merely for special instruction in school, we reach a condition which is at present so ill-defined even in the minds of educators that it seems best to fall back on the general advice that our school systems should provide just as nearly individual instruction as the public purse and managing genius can devise. Mannheim, Germany, for example, takes care of 18 per cent. outside of its regular school classes. The ideal is individual instruction for all. School authorities would be justified in providing special instruction for every degree of mental ability, if the cost would not restrict other more important social undertakings. This less degree of retardation in the group needing only school assistance should not, however, be classed as feeble-minded. We shall see later the percentages for which some authorities have considered it already advisable to provide special school instruction. We need not attempt to estimate the size of this group, as it is beyond the limit of feeble-mindedness.

The purely conative cases are not taken care of in the above estimates, which are intended for tested deficients. If the conative cases unaccompanied by intellectual deficiency should be regarded as frequent enough to replace those in the social assistance group who ultimately care for themselves, plus those subtracted by the excessive death rate, we would have a total of 1.5% of the general population feeble-minded enough to warrant social care of some sort. About 0.5% might justly be isolated. The reasonableness of this program can be judged by comparison with authoritative estimates now to be reviewed. The problem here is whether this is an unreasonable program for the diagnostician to assume as scientifically justified, remembering that these estimates are for tested deficients at 15 years of age and do not include purely conative cases which might occur above these intellectual borderlines.

E. Comparison With Important Estimates

The Social Isolation Group. We are now ready to consider some of the important estimates which throw light upon the reasonableness of the percentages we have named. First, what percentage would we be justified in socially isolating? In the United States Census Report on the Insane and Feeble-Minded in Institutions in 1910, we find that the number then actually in institutions for feeble-minded was only about 0.02% of the population. At the most frequent ages this rises to about 0.05%. It is evident that the number actually isolated is of little significance except as a check on the estimates. The report, however, refers to the special estimate made by the public authorities in Massachusetts which also included feeble-minded in state hospitals for the insane, other asylums, those reported by the overseers of the poor and those enumerated in the general population. The U. S. report says: “The census was not regarded as being complete, but it is of interest to note that if the number of feeble-minded in proportion to the total population was the same for the entire United States as it was in Massachusetts according to this census, the total number of feeble-minded would be over 200,000. Probably this may be regarded as a conservative estimate of the number of feeble-minded in the United States and would indicate that not over one-tenth of the feeble-minded are being cared for in special institutions” (205, p. 183). This estimate, which thus amounts to about 0.2%, may probably be considered as a reasonable program of expansion from the institutional viewpoint. The diagnostician who is considering the individual and not the mass must supplement it by considering who should be isolated if facilities were available. If the census bureau can contemplate institutional care for ten times those at present thus provided for, it gives us some indication of a reasonable limit as to the increase in institutional care that can be assumed to be reasonably contemplated at present.

Dr. W. D. Cornell, director of medical inspection of the Philadelphia public schools, after the personal examination of those cases which in the opinion of the teachers should be sent to institutions, places the “institution cases” at a minimum of 15 per 10,000 school children. He adds: “The number of evidently feeble-minded above 6 years of age may be said to be 1 to every 500 of the population. These figures are conservative and have been accepted by experts for years.” This then is the minimum estimate and quite clearly refers to institutional cases.

A committee of the Public School Alliance of New Orleans, of which Prof. David Spence Hill was chairman, reported in 1913 a careful census of the public school children in that city the previous year made by the teachers in co-operation with the Newcomb Laboratory of Psychology and Education. Each teacher was asked to state her opinion as to how many in her room were “feeble-minded or insane children who should be under institutional or home care, rather than in the public schools.” Also the number of backward children not in the above class “who urgently need special educational methods in special classes within the special schools.” About a fifth of the total of the 38,000 school children in the city are colored. The grand total showed 0.28% in the first class mentioned above, and 7.7% in the second. Speaking of those “thought by teachers to be feeble-minded” and needing institutional care the report says:

“The figure 0.28 of 1% coincides exactly with the estimate of the Philadelphia Teachers' Association made in 1909 in a census of 150,000 school children. Secondly, while the teacher's estimates are open to revision, nevertheless her judgment, as inevitably evidenced in her attitude toward the child, is the practically effective judgment” (157, p. 6). It is a well-known fact that teachers tend to underestimate the frequency of mental deficiency, so that it would certainly be a matter of regret if this were to continue to be the “practically effective judgment.”

Another census of the institutional type of feeble-minded made by the Director of Public Health Charities in Philadelphia and reported in 1910 enumerated 0.2% of the population as in this group. It included cases in the institutions for feeble-minded, the insane hospitals, almshouses, hospital, reformatories, orphanages and known to charity workers (168, p. 13).

One of the most careful surveys of individuals who, because of mental abnormalities, show such social maladjustment as to become the concern of public authorities was made under the auspices of the National Committee for Mental Hygiene in 1916.[^[5]] It selected Nassau County as representative of New York state. Part of the survey consists of an intensive house to house canvass of four districts of about a thousand population each. The result disclosed that 0.54% of the population of this county were socially maladjusted because of “arrests in development” and 0.06% more, because of epilepsy. This was in a population of 115,827.

The Children's Bureau in the U. S. Department of Labor in 1915 made a census of the number of “mental defectives” in the District of Columbia. The census included only those whom we have termed feeble-minded. The report states that 798 individuals, 0.24% of the population, were found to be “in need of institutional treatment; and the number reported, allowing for the margin of error in omission and inclusion, is probably a fair representation of the number in the District who should have custodial care” (88, p. 13). Over a quarter of the population of the District is colored. The census was taken in connection with plans for immediate care. The same Bureau also made in 1915 and 1916 a Social Study of Mental Defectives in New Castle County, Delaware.[^[6]] This county had a population of 131,670 and the survey disclosed 212 “positive cases of mental defect” and 361 “questionable cases,” a total of 0.44% of the general population in this county. Among the positive cases, 82.5% were in need of public supervision or institutional care. Among the questionable cases, information was obtained about only 175, and 165 of these were either in institutions, delinquent or uncontrollable, or living in homes where proper care and safeguarding were impossible.

Two other important attempts to enumerate carefully all the feeble-minded in definite areas in the United States have been made in recent years. Lapeer County, Mich., was chosen for such a study, as it was of average size and contained no large city. The census as reported in 1914, showed 36 feeble-minded from that county in the state institution and 116 others living in the county, a total of 1 from every 171 inhabitants ([145]). A special children's commission was appointed by the state of New Hampshire to investigate the welfare of dependent, defective and delinquent children. Its report in 1914 contained a section by its chairman, Mrs. Lilian C. Streeter, on feeble-mindedness ([40]). This comes the nearest to a complete enumeration for an entire state which has ever been attempted. The commission tested with the Binet scale the inmates of the State Hospital for the Insane, the County Farms, the State Industrial School and the Orphanages within the state. The borderline which it used for the scale was high. It counted all those testing three or more years retarded and under XII as feeble-minded. Taking its figures as they stand we find that they listed 947 as feeble-minded in institutions and 2,019 outside, a total of 0.69% of the inhabitants of the state. Outside the institutions the commission sent a questionnaire to all school superintendents and to chairmen of school boards, physicians, overseers of the poor, county commissioners, probation and truant officers, district nurses and charity workers throughout the state, by which means they listed 792 additional cases. This questionnaire gave the following description of the type of case it was trying to list as feeble-minded.

“The high grade imbecile, frequently known as the moron, is one who can do fairly complicated work without supervision, but who cannot plan, who lacks ordinary prudence, who cannot resist the temptations that are common to humanity. The high grade imbecile is most dangerous because, except to the expert, he is apparently not feeble-minded and is, therefore, usually treated as normal, and permitted to multiply his kind, and to corrupt the community.”

This description would tend to include cases above our isolation group. Besides the questionnaire the commission made an intensive study of 52 towns in which it says practically complete census returns were obtained by consulting doctors, school and town officials. With these supplementary cases it secured a list of 2,019 cases outside of institutions, making a total of 2,966 recorded cases within the state or 0.69% of the population. When it estimated the proportion for the entire state on the basis of the rate of canvass returns to questionnaire returns, this proportion rose to 0.95%. The commission does not advocate compulsory isolation for all of these people although it recommends custodial care for the feeble-minded women and girls of child-bearing age, apparently of the degree of deficiency represented by its criteria. This enumeration of 0.69% of the people of a state as feeble-minded is the most liberal general census of the feeble-minded in any large area. It clearly shows the trend of diagnosis since the British Census.

The Extension Department of the Training School at Vineland, N. J., states regarding estimates of the number of feeble-minded in the general population: “Conservative estimates give one in three hundred as the probable present number.” Under the discussion of estimates of the general population I have already cited Goddard's estimate which was approximately 0.3 to 0.4% and the enumeration of 0.4% by the British Royal Commission in 16 districts with over two million population. While all of these estimators are speaking broadly of the feeble-minded, in the general population, we shall not be far wrong in supposing that they are considering mainly those deficients for whom the state might well expect to provide care for life, isolating all those who cannot be eugenically guarded at home. We shall later quote the estimate of Van Sickle, Witmer and Ayres of 0.5% of the school population as “institution cases.”

Our estimate of 0.5% in the group justifying isolation on the ground of intellectual deficiency seems to be conservative and to harmonize fairly this type of estimate.

The Social Assistance Group. Passing now to the next higher group of deficients, those needing special training in order to get along with social assistance, the estimates have been based almost entirely upon the study of school children. Francis Warner was the moving spirit in the early investigations in Great Britain, which were made without tests from 1888 to 1894. The census which he directed included about 100,000 school children who passed in review before medical examiners. As cited by Tredgold ([204]) the estimate growing out of this work was that 1.26% of the school population should have instruction in special classes. Of these 0.28% required special instruction because of physical defects only ([204]).

About the same time Will S. Monroe ([155]) on the basis of a questionnaire sent to California teachers, who reported on 10,842 school children, found that they estimated 1,054 of these as mentally dull in school, 268 feebly gifted mentally, and 6 imbeciles and idiots. He summarized his conclusion as follows: “A long experience teaches that every school of fifty pupils has at least one child that can be better and more economically trained in the special institutions than in the public schools.” In his estimate of 2% he was probably thinking of care in special local schools and not permanent isolation.

A government inquiry of school teachers in Switzerland, who had charge of 490,252 school children, reported that 1.2% were so feeble mentally as to need training in special classes. Only about a tenth of this number were then being instructed in separate classes (181, p. 17).

Great Britain first gave legal recognition to the class of feeble-minded above the imbeciles in its Education Act of 1898, following a report of a departmental committee of its National Board of Education growing out of the inquiries of Francis Warner. This committee estimated the proportion of this class as approximately 1% of the elementary school population ([181]). In discussing the comparative estimates on the general and school populations I have already referred to the estimate of Tredgold based upon an elaborate analysis of the most extensive data ever collected,—that gathered by the British Royal Commission on the Care and Control of the Feeble-Minded. While the Commission's investigators enumerated 0.79% among the school as mentally defective, Tredgold's estimate based on his analysis of their report was that 0.83% of the school population in England and Wales were above the grade of imbecile but still feeble-minded (204, p. 157). The variability of the estimates collected by the Royal Commission from various cities probably indicates the subjective character of the standards of deficiency. They varied from an estimate of 0.24% of the elementary school population in Durham to 1.85% in Dublin (204, p. 159). The Commission says regarding estimates as to communities other than those reported by their medical investigator, for Newcastle the “number of feeble-minded children of school age” (morons) was 0.25%, for Leeds the estimate was 0.80%, for London 0.50% or 0.60%, for Bradford 0.50%, for Dublin about 1% and for Birmingham about 1% of the school population. Dr. Francis Warner's general estimate was 0.8%. We have thus variations in estimates from 0.25%, 0.5%, 0.80% to 1% and some 2% (167, p. 90). For the rural areas the estimates were generally less.

A careful estimate has been made with a different method by Karl Pearson on the basis of a classification by teachers of school children in Great Britain into nine different classes each especially defined and extending from the imbecile to the genius. This distribution of the children was then fitted to the normal probability curve. On this basis Pearson estimated that 1.8% would fall in the “very dull group,” defined as having “a mind capable of holding only the simplest facts, and incapable of grasping or reasoning about the relationship between facts; the very dull group covers but extends somewhat further up than the mentally defective.” Lower down would be 0.1% in the imbecile group. He says further regarding this estimate: “It is deduced from three series covering between 4000 and 5000 cases, and the three separate results are in several accord. It will, I think, be possibly useful for other inquirers, and it endeavors to give quantitative expression to our verbal definitions of the intellectual categories” ([166]).[^[7]]

In 1914 Pearson cites estimates of mentally defective children in several cities by teachers and medical officers based upon the recommendation of elementary school children for special schools and classes. These were, for London: boys, 1.59%; girls, 1.09%. For Liverpool: boys, 0.827%; girls, 0.618%. The corresponding figure for both sexes in Stockholm is 1.23%. He concludes that “something between 1% and 2% is true for England. Dr. James Kerr, Medical Research Officer, thinks that the final estimate will be nearer the latter value.”

After giving a table of the percentages at each age in the elementary schools of Stockholm, Pearson says: “Judged from this table it would seem that the most reasonable estimate of the prevalence of mental defect is to be formed when all the mental defectives have been definitely selected and the normal children have not yet begun to leave school, i. e., at the ages 11 and 12. For Stockholm this leads up to a mentally defective percentage of about 1.5” (167, p. 6-8). In another place he says that the members of special classes are selected practically for the same reason, i. e., because they are school inefficients, the bulk of whom will, no doubt, unless provided for become “social inefficients” (164, p. 48). Since some were not selected because of intellectual deficiency, our social assistance group should be somewhat smaller.

In 1909-10 the actual number in the schools for mental defectives maintained by the London County Council was 0.9% of the enrollment of the London elementary Schools ([143]). The 1912 report of the London County Council shows 7357 children enrolled in its local schools for mental defectives, which is 1.1% of the average attendance from 1912-1913 in the elementary county council schools and voluntary schools of London (144, p. 44).

Following a discussion in the Australian Medical Congress of 1911 the Minister of Public Instruction called for returns as to the number of feeble-minded in the Australian public elementary schools between 5½ and 14 years of age inclusive. The questionnaire used the definitions of the British Royal Commission as a description of the various degrees of retardation and brought returns from 2,241 of the state schools, all except 57. For their average attendance of 175,000 children, these teachers classified 1.9% as backward from accidental causes, 2% mentally dull, 0.42% feeble-minded imbeciles or idiots, and 0.6% epileptics. To this would be added 0.19% for children in the idiot asylums. The report states that “the teachers' estimates will thus be realized to be an absolute minimum, dealing only with the intermediate grades, and not including the gross cases (idiots, etc.) on the one hand and the less marked high grades of feeble-minded on the other” ([70]).

The census made by the Bureau of Health of Philadelphia through the principals of schools in 1909 covered 157,752 elementary school children of whom 1.9% above the 0.28% who could “properly be in custodial institutions 'were classed' as backward children who require special instruction by special methods in small special classes” ([168]).

A survey of the school population in the Locust Point District of Baltimore was made by Dr. C. Macfie Campbell.[^[8]] The district surveyed was, however, not considered typical of Baltimore, but was a sample of an industrial district in which the majority of families are “close to the poverty line, and too often below it.” Out of a school population of 1,281 children, 166 (13%) were “found to have special requirements on account of their mental constitution.” Among these, 22 (1.7%) “showed a pronounced mental defect, which eliminated any prospects of their becoming self-supporting.”

The city of Mannheim ([147]), which perhaps cares for its exceptional children better than any other in the world, was in 1911-1912 caring for 0.7% of the children in its Volkschule in Hilfsklassen which do not take them beyond the fourth grade. There were 12% more who were backward in school and being taught in Forderklassen where they may reach the sixth grade. Including the exceptionally bright who were also in special classes, 18% all together of its school children were not in the regular Hauptklassen of the eight grades. To these would be added those sent to special institutions. When we estimate, therefore, that we are justified at present in sending 1% of the children in school to special classes because their intellectual deficiency is such that the bulk of them cannot get along without social assistance, we are naming about the proportion already thus cared for in several foreign cities.

Among the authoritative estimates of the number of feeble-minded, which have been made by estimators who had in mind the evidence from mental tests, is that made by James H. Van Sickle, Lightner Witmer, and Leonard P. Ayres in a bulletin published by the United States Bureau of Education in 1911 ([209]). They state that, “if all children of the public schools could be ranked, it is probable that a rough classification would group them about as follows—Talented, 4%; Bright, Normal, Slow, 92%; Feeble-Minded, 4%. The 4% may for administrative purposes be divided into two groups. The lower one includes about one-half of one per cent. of the entire school membership.... They are genuinely mentally deficient, and cannot properly be treated in the public schools. They are institution cases, and should be removed to institutions. Ranking just above these are the remaining three and one-half per cent. who are feeble-minded but who could be given a certain amount of training in special classes in the public schools.” The estimate of institutional cases practically coincides with that adopted above in this paper. The extension of the term feeble-minded to include the lowest 4% seems to be extreme. The authors do not suggest what portion of these they think might require social assistance indefinitely, but are interested primarily in provision for special classes in the public schools. If the term feeble-minded were to mean only unfit for regular school classes and not socially unfit, I have already suggested that the limit for special instruction might be increased indefinitely. In Mannheim 18% are not cared for in the regular classes.

The only estimate of feeble-minded which I have found that is so large as this 4% is that of Binet. It is also intended to cover all cases that should be sent to special classes regardless of subsequent social survival. His statement as to those who are so abnormal or defective as to be suitable for neither the ordinary school nor the asylum is as follows:

“As to France, precise information has not been available until the last year, when two inquiries were held—one at the instance of the Ministerial Commission, the other organized by the Minister of the Interior. According to the former inquiry we find that the proportion of defectives amounts to scarcely 1% for the boys, and 0.9% for the girls. These percentages are evidently far too small, and we ourselves have discovered, by a small private inquiry, that many schools returned “none” in the questionnaires distributed, although the headmasters have admitted to us that they possessed several genuine defectives. In Paris, M. Vaney, a headmaster, made some investigations by the arithmetic test, which we shall explain presently, and reached the conclusion that 2% of the school population of two districts were backward. If we were to include the ill-balanced, whose number is probably equal to that of the backward, the proportion would be about 4%. Lastly and quite recently a special and most careful inquiry was made at Bordeaux, under the direction of M. Thamin, by alienists and the school medical inspectors, and it was found that the percentage of abnormality amongst the boys was 5.17. Probably the true percentage is somewhere in the neighborhood of 5. All these inquiries are comparable because they deal with the school population” (77, p. 8).

In this estimate of 5%, Binet was considering those to be sent to special classes regardless of whether or not they would require indefinite social assistance after their schooling. It is therefore not directly comparable with our estimate of 1.5% presumably or doubtfully intellectually deficient.

The estimate of Dr. Henry H. Goddard, who has done the most to introduce the Binet Measuring Scale in this country, is stated as follows: “It is a conservative statement to declare that 2% of public school children are distinctly feeble-minded, the larger part of them belonging to this high-grade group which we call morons” ([118]). In another ([114]) place he says: “The most extensive study ever made of the children of an entire school system of two thousand has shown that 2% of such children are so mentally defective as to preclude any possibility of their ever being made normal and able to take care of themselves as adults.”[^[9]] The study to which he refers gives individual results with the Binet 1908 tests made on 1547 school children in the first six grades (114, p. 43). Since the sixth grade does not include the better children who are twelve years or over in age this group is clearly selected in such a way that it would show an excessive percentage of mentally retarded children. We find in the investigation referred to that he says: “Then we come to those that are four years or more behind their age, and here again experience is conclusive that children who are four years behind are so far back that they can never catch up, or in other words, they are where they are because there is a serious difficulty which can never be overcome—they are feeble-minded. They constitute 3% of the children in these grades.”

Since we have a random selection of school children in his table for only those children who are 6 to 11 years of age inclusive, I find that only 1% at these ages are retarded four years intellectually. On his own basis, therefore, 3% is evidently too large an estimate. Later he seems to have reduced his estimate to 2% of the school population. Of those who test in the lowest 1.5% including our doubtful group, I believe that there is no clear evidence that more than 1% will require even social assistance as adults.

Many more estimates of the number of feeble-minded among school children might be cited, but they would add little to these authoritative samples. At the present time an estimate by health officers or teachers who are not familiar with the results of mental testing has little significance, as the whole complexion of the problem has been changed since the work of Binet and Simon.[^[10]] We may, however, cite three estimates based upon familiarity with test results, which fairly cover the range of estimates among school children. In connection with the Springfield, Illinois, survey conducted by the National Committee for Mental Hygiene under the direction of the Russel Sage Foundation, we find that three typical schools with a total of 924 pupils were studied. The report states that “the mentally defective children” constituted 3.8% of the number in attendance in March. The number of children in the schools examined, for whom instruction in special classes would be desirable, is about 7% of the entire enrollment of these schools (203, p. 10).

In connection with the Stanford Version of the Binet Scale, Dr. Lewis M. Terman says: “Whenever intelligence tests have been made in any considerable number in the schools, they have shown that not far from 2% 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 more we learn about such children, the clearer it becomes that they must be looked upon as real defectives (57, p. 10). Again in placing the borderline for feeble-mindedness” with the Intelligence Quotient used, he suggests that “definite feeble-mindedness” lies below an I. Q. of 70 which with 1000 quotients was found to exclude about the lowest 1%. Above this is a group with I. Q.'s 70-80 which he describes as “borderline deficiency, sometimes classifiable as dullness, often as feeble-mindedness.” This group would include, as judged by the results of these tests, over 4% more.

Dr. Wallin, who has had wide experience in testing both school children and defectives, states: “I will venture the assertion, after years of teaching in the public schools and clinically examining public school cases, that the oft-repeated statement that 2% of the general school population is defective (if by this is meant feeble-minded), exaggerates the real situation. The actual number is probably about 1%” (211, p. 149).

After reading a paper on “A Percentage Definition of Intellectual Deficiency” before the American Psychological Association in 1915 ([151]), I was pleased to discover that Prof. Rudolf Pintner and Donald G. Paterson were also about to propose a percentage definition of feeble-mindedness for those who are dealing with mental tests ([44]). While their idea seems to be fundamentally similar, their paper shows that their conception is to be sharply distinguished in several particulars from that which I am advocating. They would limit the use of the term “feeble-mindedness” to individuals who test in a rather arbitrarily chosen lowest percentage of the population. As opposed to this I suggest continuing the present social definition of feeble-mindedness and supplementing it, for the purpose of aiding in the diagnosis, by indicating the social significance of those testing in certain lowest percentages. Such tested deficients I designate as “intellectually deficient.” It is important to consider their statement and to note what percentage they have chosen to regard as feeble-minded. They say:

“It is in order to avoid this vagueness and uncertainty attaching to the term that we suggest a definite psychological concept. The lowest three per cent. of the community at large, that is, the lowest as determined by definitely standardized mental tests, are to be called feeble-minded. Such a definition will be unambiguous and the dividing line between this and other groups will become clearer and clearer as we increase the accuracy of our measuring scales and the adequacy of our standardizations. Furthermore, if evolution is raising the degree of intelligence the three per cent. at the lower end will still remain, for, whatever the degree of their intelligence may be, they will still be feeble-minded as compared with the normal.

“Such a definition will in addition restrict the term to such as are lacking in intelligence and will differentiate them from the moral defectives and the psychopathic personalities, which are at present often confused with the group that we propose to call feeble-minded. An individual may be at the same time a moral defective and feeble-minded, but there is reason to believe that moral deficiency may exist without such intellectual defect as to warrant a diagnosis of feeble-mindedness. The same may be said of the psychopathic personality.

“The further question, whether all those coming within the proposed definition of feeble-mindedness are to be confined in institutions, is purely social and will be determined by the social needs of each community and does not concern us here. It is obvious that many more in addition to the feeble-minded as defined by us will require the restraint of an institution, even though no real mental defect exists.

“It is immaterial for the purposes of this hypothesis whether three or a smaller or larger percentage be designated as feeble-minded. The important point is the agreement upon some fixed percentage, and we have chosen three per cent. as covering presumably all the cases of marked mental deficiency. A brief glance at the chief estimates of the number of feeble-minded in civilized communities would indicate that our percentage is somewhat higher than the conservative writers give, but we shall show later on that it is much lower than the results obtained from groups of children tested by intelligence scales” (44, p. 36).

With those who understand that deficiency is mainly a question of degree, it would seem that there might be some agreement as to the plan for defining tested deficiency. In order to make this plan more useful to those dealing with the social care of the feeble-minded, it would be necessary to supplement the bare percentage definition by relating it to expectations of social failure somewhat after the manner I have attempted. In particular it will gain its main value for diagnostic purposes, it seems to me, if the percentage is so chosen that it may receive the support of conservative scientific opinion. To be most useful it seems evident, also, that the percentages must be chosen with regard to the sort of social care which it is anticipated would be justified for the particular degrees of deficiency.

Let us recall the percentages suggested to harmonize the estimates: the lowest 0.5% to be regarded as presumably deficient enough to justify isolation and the next 1% as doubtful, but low enough to warrant special training and probably requiring indefinite social assistance. If these percentages for tested intellectual deficiency have been shown to be fairly conservative estimates in the light of the authoritative judgments with which they have here been compared, the laboriousness of this comparison has been worth while. Further light upon the social assistance group may be thrown by the study of the success of those children who have already had the advantage of training in local classes for the deficient.

F. The Ability of the Mentally Retarded, Especially Those Receiving Special Training.

That we are not justified in isolating all whom we class as feeble-minded is best indicated by the evidence as to the number of these sent to special local classes for deficients who are able to float socially with the assistance of capable after-care committees. A fair picture of the present situation may be obtained by thinking of these pupils in the help-classes and schools as representing about the next 1% above those who have been isolated in institutions. With this picture in mind let us see what has been the outcome of their special instruction and social assistance thereafter.

In his book on Les Enfants Anormaux, Binet collected the evidence available at that time (77, p. 140). He says:

“Mme. Fuster, after a stay in Germany, where she visited some Hilfsschulen and Hilfsklassen (literally, 'help-schools' and 'help-classes') made a communication to the Société de l'Enfant, from which it appears that in the case of 90 classes for defectives in Berlin, 70% to 75% of the defective pupils who were there became able to carry on a trade; 20% to 30% died in the course of study, or returned to their homes, or were sent to medical institutions for idiots.

“According to a more recent inquiry, made under the auspices of M. de Gizycki at Berlin, and published in a book by Paul Dubois, 22% of the children were sent home or to asylums; 11% were apprenticed; 62% worked at occupations which required no knowledge and yielded little pay (laborers, crossing-sweepers, ragmen). If we add together these two last groups, we reach a proportion of 73% of defectives who have been made, or who have become more or less useful....

“Dr. Decroly has kindly arranged at our request a few figures relating to the occupational classification of the girls discharged from a special class in Brussels.... Finally, then, out of nineteen feeble-minded subjects, regarding whom particulars have been supplied, one-half, or 50%, have been apprenticed, or more than half, 75% if we count the defectives who 'work....'

“Through the intervention of an inspector, M. Belot, we have inquired of twenty heads of schools what has become of the defectives whom they notified to us two years ago. We have made these inquiries with regard to sixty-six children only.... If we subtract the two first groups, those about whom the particulars are wanting, and those who have not yet left school, there remain twenty-seven children, of whom seventeen have been apprenticed, or 76%.... Now this proportion is, by an unexpected agreement, identical with that obtained in the classes of Berlin and Brussels.”

A more recent report concerning the Hilfsschulen in Berlin by Rector Fuchs is in close agreement. It indicates that from 70% to 80% of the former pupils of these schools make a living after they leave school.

To compare with these reports indicating that about three-fourths of those leaving the special schools of Paris, Berlin and Brussels by social assistance attain occupational classifications, we have less favorable reports from Great Britain. Shuttleworth and Potts (181, p. 23) say:

“At the Conference of After-Care Committees held in Bristol on October 22, 1908, a paper read by Sir William Chance, Chairman of the National Association for the Feeble-Minded, dealing with the reports of the After-Care Committees of Birmingham, Bristol, Leicester, Liverpool, London, Northampton, Oldham and Plymouth. The combined statistics from the nine centers showed that 22% of those who had attended special schools for the mentally defective were in regular work, and 6.8% had irregular work.... To illustrate the necessity for continuous supervision and the futility of temporary care, we cannot do better than quote the records of the Birmingham After-Care Committee, as embodied in their report for 1908, after seven years work. It was found that, 'out of 308 feeble-minded persons who have left school and are still alive, only 19.8% are earning wages at all, and only 3.9% are earning as much as 10 s. per week'” ([181]).

Tredgold summarizes other data on this question of industrial success as follows:

“We may next turn to the reports of 'After-Care' Committees regarding feeble-minded (moron) pupils of the special schools. In London the proportion of pupils known to be in 'good or promising' employment was 37.5%. Two years previously it had been 45.7%, and Sir George Newman, the Chief Medical Officer to the Board of Education, attributes the falling off to two causes—firstly, insufficient after-care; and secondly, the two additional years. He remarks: 'The longer the test the more severe it is.' In Birmingham, the 'After-Care' Committee compiled information regarding 932 cases which had passed through the schools during the previous ten years. Of these, excluding the normal and dead, 272, or 34%, were engaged in remunerative work. At Liverpool, of 712 children passing through the hands of the 'After-Care' Committee during a period of six years, 85, or 11.9%, were doing remunerative work.

“Finally we may refer to some figures concerning 'After-Care' work compiled by Sir William Chance from the returns of the National Association for the Feeble-Minded. These were based upon an inquiry made of sixteen centers of the Association, and referred to a total of 3,283 persons. Of this number, 798 were doing remunerative work, 89 were 'doing work, but not reported;' 202 were useful at home; and 941 were returned as 'useless members of society.' If we exclude 340 who were transferred to normal schools (not being feeble-minded), we have 27% engaged in remunerative work.

“With regard to the term 'remunerative work,' however, it is to be remarked that the person employed is not being paid the standard wage. On the contrary, it is my experience that this is practically never the case, and this is corroborated by the observations of the secretary of the Birmingham center, who says: 'Although some of our cases have been at work for more than ten years, only 34 of the whole number (173) earn as much as 10 s., 2 d., per week. Of these only 6 earn as much as 15 s., and only 2 earn 20 s., which is the highest wages earned.... While it is not very difficult for some of our higher-grade cases to get work when they first leave school, it is almost impossible for them to retain their situations when they get older, and the difference between them and their fellows becomes accentuated. Uncontrolled and often quite improperly cared for, they rapidly deteriorate, the good results obtained by the training and discipline of the special school being under these circumstances distinctly evanescent.... There are few workers over twenty years of age'” (204, p. 425, 435).

The 1912 report of the London County Council ([144]) covers those who left its special schools for mentally defective children during the years 1908-1912 inclusive. These schools have accommodation for about 1% of the elementary school enrollment. Of 2010 children who left these schools during these five years, and who were still alive, 1357 were employed and 311 more employed when last heard from, a total of 79% employed at last accounts. Those out for five years show about the same proportion employed. This is a more favorable showing and fairly in line with the results of other European help-schools. The average weekly wages of those employed ranged from 4 s. 6 d. for those just out to 10 s. 10 d. for those leaving five years before. A considerable proportion who live at home thus have been meeting their necessary living expenses as the result of this special training and subsequent assistance.

Dr. Walter E. Fernald reported to the British Royal Commission on the Care and Control of the Feeble-Minded concerning the inmates of the institutions for feeble-minded in the United States. These institutions receive a much lower grade of cases on the whole than the local help-schools abroad: (83, Vol. VIII, p. 159)

“Some of the institutions where only the brightest class of imbeciles are received, and where the system of industrial training has been very carefully carried out, report that from 20% to 30% of the pupils are discharged as absolutely self-supporting. In other words at other institutions, where the lower grade cases are received, the percentage of cases so discharged is considerably less. It is safe to say that not over 10% to 15% of our inmates can be made self-supporting, in the sense of going out into the community and securing and retaining a situation, and prudently spending their earnings.... But it is safe to say that over 50% of the adults of the higher grade who have been under training from childhood are capable, under intelligent supervision, of doing a sufficient amount of work to pay for the actual cost of their support, whether in an institution or at home.”

The wages of the women at the Bedford Reformatory before entering prostitution as given by Davis (133, p. 210) have a direct bearing on the earning capacity of the higher grade feeble-minded. The Binet tests of Bedford women by Weidensall indicate that about 38% of the successive cases admitted to Bedford test in the lowest 0.5% intellectually, and 75% in the lowest 1.5% intellectually. Davis' table shows that for 110 whom she classes as mentally low grade cases at the reformatory, the median wage of those in domestic service, as claimed by the women, was nearly $4.50 before entering prostitution. These feeble-minded women, if their statements of earnings can be accepted, are therefore feeble-minded by reason of their low intelligence plus delinquency, and not by reason of inability to earn the necessities of life. The best of these mentally low grade cases earned as high as $5.00 in addition to board and lodging in domestic service and $25.00 outside of domestic service.

In this country we have fewer studies of the results of training the mentally retarded in special local classes and schools. Miss Farrell has made a preliminary report of 350 boys and girls out of the 600 children formerly in the ungraded classes in New York City during the preceding 8 years ([102]). Omitting seven whose status was unknown and 10 who had died, only 6% were known to have failed to survive socially with assistance. These were in penal or other institutions. On the other hand a strict analysis of her returns shows only 28% earning $5.00 a week or more and thus possibly surviving independently. Of the above group of 333, 86 were at home, 192 employed, 31 unemployed and 3 married.

In Detroit among 100 children over 16 years of age who had attended its special classes and been out of school not over 5 years, 27 had been arrested, but 39 of the boys had been at work and received an average wage of $7.00 per week, while 16 girls had averaged $3.75 in weekly wages, although few held their positions long ([97]).

Bronner ([6]) compared a random group of thirty delinquent women at the detention home maintained by the New York Probation Association with an intellectually similar group of 29 women all of whom had been earning their living in domestic service and none of whom had been “guilty of any known wrong doing.” The delinquents were 16 to 22 years of age while the servant group was somewhat older. Only two or three of the delinquent group were worse than the poorest of the servant group in any of the five intellectual tests, so that, if more than this number were intellectually deficient, they were no more deficient than those who had survived in society. No Binet scale records were published so that we have no means of determining how many of these delinquents might fall within either of our deficient groups.

The principal deduction from this evidence on the earning capacity of those of low intellectual grade is a caution against demanding the social isolation of all the intellectually weak until we have more definite information as to what portion of them are able to live moral lives, as well as earn their living with social assistance, without being cared for entirely in isolation colonies. That a significant number of the lowest 1.0% intellectually next above the lowest 0.5% have led moral lives and have shown considerable earning capacity after attending special schools, when they are given proper after-care, has probably been demonstrated. They should, therefore, be treated as an uncertain group whose feeble-mindedness would never be decided purely on the ground of the intellectual tests. Most of them will, however, probably be found mentally deficient enough to need at least social assistance and protection.

In concluding this summary on the estimates of the frequency of feeble-mindedness, it need only be added that so far as concerns the use of the percentage definition for fixing the borderline in any particular system of tests the percentages chosen are not essential to the plan. The principles of the method apply whatever percentages might be adopted. For such important purposes as the comparison of the relative frequency of deficiency in different social groups and harmonizing the investigations with different mental scales, agreement upon a particular percentage is not essential. In diagnosis, of course, it is a matter of fundamental importance in order that injustice may not be done individuals. For this reason the estimate should be conservative, possibly more conservative even than our tentative 0.5% at 15 years of age. Any investigator who disagrees with the above estimates of the degree of tested deficiency justifying isolation may substitute X per cent. with a doubtful region extending Y per cent. further. Provided such a census were legally authorized and funds available it would be not impossible to get a reliable determination by a house to house canvass showing the number of adult deficients, say 21 years of age, in typical communities, who were not able to survive socially without assistance. This number would then give the key for a conservative percentage and the movement for early care would be immensely advanced.

With the recent introduction of psychological tests into the cantonments of the national army, the goal of symptomatic borderlines as determined by objective tests seems to be almost at hand. Since the men are brought practically at random to the camps by the draft and are under military command, it may be possible to find out the social history of a large enough group at the lower limit of tested ability to establish the question of the necessary capacity for independent moral and social survival. These borderlines could then be transferred from the army tests to positions of equivalent difficulty in other test systems.

The remainder of this study will show some of the advantages of the percentage definition for fixing the borderlines with a system of tests and the result of applying such an interpretation to the particular problem of delinquency. The advantage in increased definiteness should already be evident. When a person is classed as presumably deficient it will mean that he is in the lowest 0.5% in intellectual development or within the lowest 1.5%, if he is a persistent delinquent.

[5]. Aaron J. Rosanoff. Survey of Mental Disorders in Nassau County, New York. Publication No. 9, National Committee for Mental Hygiene, 1917.

[6]. Emma O. Lundberg. A Social Study of Mental Defectives in New Castle County Delaware. U. S. Dept. of Labor, Children's Bureau, Publication No. 24, 1917, pp. 38.

[7]. This statement in 1906 seems to be the earliest attempt at a quantitative definition of deficiency. As I discovered it after the present monograph was practically completed, it furnishes evidence of the natural tendency of attempts at more exact definition to take the percentage form.

[8]. C. Macfie Campbell. The Sub-Normal Child—A Study of the Children in a Baltimore School District. Mental Hygiene, 1917, I, 96-147.

[9]. Italics mine.

[10]. The report of the Massachusetts Commission on Mental Diseases (Vol. I, p. 198) shows that social agencies systematically using mental tests reported 19.2% as mental cases, while those using examinations only for obvious cases reported 1.3%.

CHAPTER V. ADAPTING THE PERCENTAGE DEFINITION TO THE BINET SCALE

Sufficiently large random groups have not been tested with any development scale to make the determination of the borderline on the scale more than tentative. Such borderlines must be looked upon as temporary descriptions to be used in aiding diagnosis until more data are available. Nevertheless, the percentage method of procedure seems to be an improvement over other plans of stating the borderline. So far as the Binet 1908 scale is concerned, when we supplement Goddard's results with 1500 school children by the data for the lower limits of a random group of 653 15-year-olds which we tested, the limits on the scale for passable intellects defined by the percentage method will be found, I believe, not only more conservative, but more reliable than those in current use. Moreover the intended meaning of such borders becomes clear.

A. The Border Region for the Mature.

(a) Indication from a random group.

The passing limit for adults is unquestionably much more important than that for children since any child who once passes this limit is assured, generally speaking, of social fitness so far as intellect is concerned. He has attained a position intellectually which is sufficiently good to enable him to get along without social assistance unless he is especially deficient in will. This borderline for the mature has been so thoroughly neglected that in none of the common published forms of the Binet scale, except the new Stanford Scale, is there an attempt to define it. This seems almost incredible in view of the general use of the Binet method in diagnosing feeble-mindedness. To be sure, there are discussions of this upper limit, as we shall see, but they have usually not been embodied in the actual directions accompanying the scales which get into the hands of amateurs. Most of these directions content themselves with describing borderlines for children with no caution about the final lower limit for social survival.

The borderline for the mature is the first difficulty which a court examiner will encounter when he attempts to obtain assistance from an objective system of measurement. Very little experience will convince one that it is not enough to describe the deficient ability of an adult in terms of years of retardation. It is widely agreed that at some age during adolescence practically all the mental processes are available that will be found in the mature. From that time the advance in ability is made by attaining greater skill in specific activities through training and by increasing knowledge, rather than through a native change in the form of thinking. If mental tests mainly reach capacity for thinking, as they aim to do, rather than amount of knowledge or skill in specific work, then we are conservative in using a randomly selected group at 15 years of age for approximating the borderline on the scale for the mature.

In connection with the new Stanford Scale, Terman says: “Native intelligence, in so far as it can be measured by tests now available, appears to improve but little after the age of 15 or 16 years. It follows that in calculating the I Q (intelligence quotient) of an adult subject, it will be necessary to disregard the years he has lived beyond the point where intelligence attains its final development. Although the location of this point is not exactly known, it will be sufficiently accurate for our purpose to assume its location at 16 years” (57, p. 140).

Yerkes and Bridges in connection with their Point Scale say, “it seems highly probable that the adult level is attained as early as the sixteenth year” (225, p. 64). Kuhlmann ([138]) used 15 years as the divisor in calculating the intelligence quotient of adults and Spearman thinks that the limit of native development is reached about 15 years ([184]). He says, “That mental ability reaches its full development about the period of puberty is still further evidenced by physiology. For the human brain has been shown to attain its maximum weight between the ages of 10 and 15 years” ([184]). For the last statement he quotes Vierordt. On the contrary Wallin thinks that we need more evidence for the correctness of these hypotheses before choosing a fixed age as a divisor for adults (215, p. 67).

We are not interested in determining a divisor for an adult intelligence quotient but in fixing a conservative borderline for the mature. Admitting that the mental capacity of those 15-year-olds at the lower limit may not be like adults, nevertheless adults would be more likely to be better than worse. Borderlines for the 15-year-olds, should, therefore, be safe for adults. Moreover, the lower limits with a truly random group of 15-year-olds would probably be more reliable than an assorted group of adults subjectively chosen from different walks in life and combined in an effort to represent a random mature group. The Stanford Scale utilizes such combination of selected adults. It seems, therefore, that we are justified in utilizing the lowest percentages of randomly selected 15-year-olds as a reasonable criterion for describing the limits for adult deficiency. Surely adults below this lower limit for 15-year-olds would have questionable intellectual capacity.

The borderline for the mature being the crucial feature of a developmental scale when used for detecting feeble-mindedness, it seemed imperative to us that some effort should be made to obtain records with a random group of older-age children or adults. Goddard's results with school children were not significant above eleven years of age since the personal examinations were confined to children in the sixth grade or below. The twelve year old group in the sixth grade clearly omits the best 12-year-olds, so that the percentage method would have no significance applied to his figures for children above 11 years of age. Moreover it was obvious that the group of public school children 15 years of age or older would not give a picture of the lower end of a random group since many children drop out of school at 14. On the average those that leave are undoubtedly of lower ability than those who remain.

The most valuable data on the borderline for the mature would come from mental examinations of large random groups of adults. The impossibility of gaining the consent of adults for such examinations puts this plan out of consideration. Perhaps the next best method would be to examine all the children of 15 and 16 years of age in typical communities. It happened that we could approach this result in Minneapolis since we there had an excellent school census made from house to house covering all children under 16 years of age. The Minnesota law requires school attendance until 16 years of age unless the child has graduated from the eighth grade. Under the able direction of Mr. D. H. Holbrook of the attendance department the census of children of school age had been made with unusual care. All the children living in each elementary school district in the city were listed in a card index regardless of whether they were attending public, parochial or private schools, or had been excused from attendance for disability or for any other reason. Since we only needed to be sure to examine the lowest few per cent. of the children in ability this group of 15-year-olds could be tested by examining all those children in typical school districts in the city who had not graduated from the eighth grade. A third of the 15-year-olds were still in the eighth grade or below. Neither the compulsory attendance law nor the census would have reached the 16-year-old adequately. In most states even the 15-year-olds would have been above the compulsory school age.

There were 653 children, (322 boys,) 15 years of age living in the seven typical districts which were selected objectively for study. Among these there were 196 who had not graduated from the eighth grade. All of these latter children were examined, except one who could not be tested as she was in a hospital on account of illness. Quite a number of the children were in parochial or private schools, two were followed to the state industrial school and a number were examined at home. In order to be sure that we had not missed any institutional cases in these districts the complete list of Minneapolis children at the State School for Feeble-Minded was gone through to get any of low ability who might have been missed.

The seven districts in which the children were to be studied were chosen, with the idea of avoiding any personal bias in their selection, by taking them alphabetically by the name of the schools, except that no district was taken where the normal school attendance of the district was affected by inadequate school facilities so that children had to be transferred either to or from that district to other schools in order to meet crowded conditions. It happened fortunately that none of these schools represented extreme conditions in the city. The average percentage of children in the 69 elementary schools of the city retarded in school position below a standard of 7 years in the first grade, 8 in the second, etc., was 24.1% with a mean variation of 6.5%. The percentages retarded in the schools studied were as follows: Adams, 22.7; Bryant, 21.1; Calhoun, 21.7; Corcoran, 29.4; Douglas, 20.4; Garfield, 18.6; Greeley, 26.4.

Kuhlmann's adaptation of the 1911 scale ([135]) was used as a basis for the examinations, supplemented by the 1908 scale wherever tests had been changed so that other forms of the tests were found in either Kuhlmann's ([136]) or Goddard's ([110]) adaptations of the 1908 scale. Since test results with the 1908 scale provide the most data for describing the borderline for the immature, our plan was to use the 1908 form of a test first when the procedure had changed. The supplementary directions were arranged for each age so that the testing could proceed methodically and the results be scored under either the 1908 or 1911 scale with the least possible disturbance of each test. Over a third of the children were tested by myself. The rest were tested by three advanced students in psychology. It is a pleasure to express my thanks to these assistants, Miss Rita McMullan, Miss Lucile Newcomb and Miss Florence Wells. Besides having had brief experience in dealing with exceptional children, they practised testing under my observation until the tests could be given smoothly and I was convinced of their ability to follow directions intelligently and make full records with reasonable accuracy. The results of the tests were all carefully gone over and scored by me. So far as I can judge, the results are quite as accurate as any other published tables, although one must always consider the possible effect of errors of testing. Separate rooms were provided at the schools or homes so that the child could be alone with the examiner during the testing.

In attempting to define the borderlines on these scales we might either state the exact scale position in tenths of a year below which 0.5 and 1.5% of the cases fall, or we might merely attempt at present to state the borderlines in rounded terms of years on the scale. The latter plan is the one I have adopted for several reasons. The main reason is that I wish to emphasize that these are still rough boundaries. Besides that, however, a study of the results shows that the cases do not distribute by separate tenths of a year so that exactly these percentages could be picked off, without a questionable smoothing of the curves while the rounded years approach these limits fairly well.

It seems to me that it is best at present to be carefully conservative in describing these borderlines, so that I have chosen them from the available data at the nearest rounded age position which is reasonably sure not to catch more than these limiting percentages. Throughout the tables I have also followed the published directions for the 1908 scale in classing the person in the intellectual age group in which he finally scores all or all but one of the tests. I recognize, of course, that this is an arbitrary limit; but it is the limit fixed by the usual printed directions going with the 1908 scale, which is the only one thus far standardized for the immature on the percentage basis. For those who wish to calculate other borderlines or reconstruct the individual tests of the scale I have provided the complete data for each individual both for the 1908 and 1911 scales in Table XXI, Appendix I. The table also gives the exact ages and school grades of each child.

The summary of the results with the tests for those testing under XII is given in Table III. Life-age[^[11]] at the last birthday and not the nearest life-age is used in the table. The children were all between their 15th and 16th birthdays. Following the directions published with the scales, the basal age for calculating the results in the table is taken as the highest at which all or all but one test are passed for the 1908 scale, and the highest at which all were passed for the 1911 scale. Two-tenths is allowed in the table for each test passed above the basal age and 0.1 for an uncertain answer. The children were tested by the long method, beginning with the mental-age group at which the child could pass all the tests and continuing to that age group in which he failed in all.

TABLE III—Test Borderlines with Randomly Selected Minneapolis 15-year-olds

Percentages of 653 living in these districts, 196 of whom had not graduated from the eighth grade and were tested. Scored by the Kuhlmann and Goddard 1908 Binet scale and by the Kuhlmann 1911 scale.

Thrown into percentages of the group of 653 children living in these districts, it is evident that a test score of XI raises any person above the group of intellectual deficients. The percentage that tested this low, i. e., under XI.8, with the 1908 scale, was 10.0 (65 cases) and this would probably be increased if those who had graduated from the eighth grade had also been tested. The percentage testing under the same position in the 1911 scale is 8.1 (53 cases). With the 1911 scale there were 32 additional cases testing XI.8 or XI.9. The table indicates that 0.2% of the 15-year-olds tested below IX.8 with the 1908 scale, and 0.5% with the 1911 scale. This defines our scale borderline for the mature who are presumably deficient as below test-age X. These positions are near enough to the lowest 0.5%. The group testing of uncertain ability, age X, (strictly speaking between IX.8 and X.7 inclusive,) includes 0.7 to 0.9%. We thus approach fairly well the rounded age positions which exclude 1.0% above the lowest 0.5%. The total number testing in presumably and uncertain groups is thus 1.1%, 7 cases out of 653, for the 1908 scale and 1.2%, 8 cases, for the 1911 scale. This is to be compared with the percentage definition that the lowest 1.5% are either presumably deficient or uncertain.

At present we are entitled to assume that adults testing below XI, i. e., below X.8, are so low in intellectual development that it is a question whether they have sufficient equipment to survive socially. Fine discriminations with the Binet scale are not possible with our present knowledge. So far as our information goes, if we use the percentage method of defining intellectual deficiency, we may say that adults who test X are in an uncertain group in intellectual ability, with the probability that they will require more or less social care, while those who test IX are deficient enough to need continuous care unless the evidence of the test is contradicted by other facts or is accounted for by the existence of removable handicaps.

It is perhaps not necessary to call attention to the fact that X and XI are used here merely to refer to positions on the Binet scale without regard to what per cent. of ordinary 10-and-11-year-old children attain these positions. For example, XI does not imply that most of the children of eleven years of age are above this borderline. Table IV, to be given later, suggests that hardly two-thirds of random 12-year-old children pass this position on the 1908 scale and not half of the 11-year-olds. Thorndike regarded X.8 as normal for a child of 11.6 years of age. ([200])

So far as the determination of intellectual deficiency is concerned we should note with emphasis that placing the limit of passable intellects at XI for adults almost entirely removes the common objection to the Binet scale on account of the difficulty of the older age tests. The older age tests become of little consequence because the best of the deficient group have a chance at tests in at least two groups above those of mental age X, so that they can increase their score by passing advanced tests as they could not if they had to test XII.

As a check upon the borderline for those presumably deficient, it is important to note that the only case which tested below this borderline with the 1908 scale was a girl in the 4B grade. She tested exactly IX with each scale and was the only child in the group who was below the fifth grade in school. There can be no question that she was mentally deficient. On the other hand in the group which tested X or above there are several cases which it would be unjust in my opinion to send to an institution for the feeble-minded without some other evidence of mental weakness. Half of them, for example, are in the seventh grade. In Minneapolis this is not as significant as it might be in other cities, since pupils are rarely allowed to remain more than two years in the same grade whether they are able to carry the work of the next higher grade or not. Pupils in higher grades may not always be able to do even fifth grade work.

The evidence from the institutions for the feeble-minded indicates that less than 5% of their inmates test XI or over. Of 1266 examinations at the Minnesota School for Feeble-Minded, 3.8% ([154]); of 378 examined at Vineland, 3.2% ([113]); of 140 consecutive admissions examined by Huey at Illinois, 5.7% ([129]). To be sure, a goodly number of these inmates are not eleven years of age, but a majority of them are at least that old and many are older. Of 280 children in the Breslau Hilfsschulen, Chotzen ([89]) found none reaching XI, and only six who tested X. These few cases in institutions reaching XI or over may well come within our class of those feeble-minded through volitional deficiency.

Goddard's description of the children at the Vineland school for feeble-minded who tested XI with the 1908 scale hardly sounds like an account of social deficiency. He says:

“In the eleven year old group we find only five individuals, but they are children who, for example, can care for the supervisor's room entirely, can take care of animals entirely satisfactorily, and who require little or no supervision. They are, it is true, not quite as expert or trustworthy as those a year older, and yet the difference is very little and the two ages can probably be very well classed together” ([113]).

The studies of groups are more important for fixing our general rules than individual examples. We must always expect to find exceptional cases where the brief intellectual tests given in an hour or less are not adequate, especially if the testing has been interfered with by the person's emotional condition at the time or by deliberate deception. A number of illustrations have been reported of successful adults who have tested X under careful examinations. Such, for example, are three cases of successful farmers tested by Wallin ([215]) and a normal school student tested by Weidensall ([59]). There are two examples of persons testing IX with the Binet scale and yet earning a living. Such is the case related by Dr. Glueck of the Italian immigrant making two trips to this country to accumulate wealth for his family by his labor ([109]), and the case of the boy reported by Miss Schmidt ([179]). These cases should make us cautious, but they are so rare that it seems best to treat those testing IX at least as exceptions.

The group studies confirm our suggestion that a borderline of X or below will bring in for expert consideration nearly all adults who are feeble-minded from a lack of intellectual ability, while testing IX is a fairly clear indication of such serious deficiency as to justify isolation. That testing X, in the absence of other evidence of conative disturbance, places the case only in an uncertain region so far as isolation is concerned is best indicated by the fact that 1.1% to 1.4% of these 15-year-olds tested this low. We have good evidence that many in special classes, which contain only about the lowest one per cent., afterwards do float in society with or without social assistance. They cannot be presumed to require isolation, as I showed in the previous chapter. It is better to say at present that those testing X require evidence of their deficiency before isolation, except in special classes, is justified. The test diagnosis alone is too uncertain, even when there are no removable handicaps.

As to the reliability of these borderlines, too much emphasis can hardly be put upon the fact that they have been determined for only a single group of 653 in a single community. They are undoubtedly not the exact borderlines, although they are the most probable percentage estimates we have at present and were obtained in a group that was as nearly unselected as it is possible to obtain. The method of selection was perfectly objective and excluded no feeble-minded children of this age living in these school districts.

The theory of sampling applied to percentages ([228]) enables us to say that the standard deviation of the true lowest 0.5% in samples of this size made under the same conditions would not be more than 0.28%.[^[12]] That is to say, if our result were only affected by the size of our sample the chances are about two out of three that the border of the true lowest 0.5 per cent. would lie between the border of the lowest 0.22% and the lowest 0.78% of a very large sample. Assuming that the distribution in this sample represented that of communities generally, the chances would be two out of three that the true border of the lowest 0.5% for like groups in like communities examined under the same conditions would lie between IX.0 and X.6 or X.4 on the 1908 and 1911 scales respectively. Moreover, the chances that a case in the lowest 0.5% in this sample would be above the doubtful group in a larger sample, i. e., get above the lowest 1.5%, would be about 1 in 10,000. On the other hand, the chances that a case above the true lowest 1.5%, i. e., above the uncertain group, would get into the lowest 0.5% in a larger sample, i. e., be classed as clearly deficient intellectually, would be about 18 in 1,000.

So far as the theory of sampling goes it would seem that these borderlines for the mature are sufficiently accurate for correcting present practise. On the other hand, the conditions in Minneapolis so far as deficiency is concerned are probably better than in the country as a whole, so that the borderlines here described might very well exclude more than the lowest 0.5% and 1.5% in the country at large. But if we shifted the definition so as to exclude the lowest 0.2% and 1.1% (the percentages empirically found below the limits described), the borders on the Binet 1908 scale would not be changed from the rough measures IX and X which are as accurate as we should expect to define our limits with the present data.

(b) The Present Tendency Among Examiners.

Comparing the suggestions as to the borderline for the mature which have heretofore been made, we find that they have gradually approached the boundary now suggested by the percentage method. In 1910 the American Association for the Study of the Feeble-Minded adopted a tentative classification in which the upper limit of the feeble-minded included those “whose mental development does not exceed that of a child of about twelve years” ([64]). This was based mainly on the fact that Goddard had found no case at the Vineland school for feeble-minded which tested higher than XII. Huey later than this found only two such cases at the institution at Lincoln, Ill., and Kuhlmann only ten cases at the Minnesota State School for the Feeble-Minded.

There was an early statement by Binet which referred to the practise in Belgium of regarding older school children as deficient when they were three years retarded in their school work (77, p. 41). This practise may have also contributed to this formulation by the American Association. Binet, however, regarded a child of the mentality of twelve as normal. In 1905, before his tests were arranged in age groups, he said:

“Lastly we have noticed that children of twelve years can mostly reply to abstract questions. Provisionally we limit mental development at this point. A moron shows himself by his inability to handle verbal abstractions; he does not understand them sufficiently to reply satisfactorily” (76, p. 146).

It is important to consider how the suggestion of XII as the upper limit of feeble-mindedness for adults got into the early practise in this country as the lower borderline for the mature. It is the most serious error which has marred investigations in this field. It seems to have been a case of repeated misunderstanding on the part of examiners for which nobody in particular was to blame. So far as I can determine nobody stated directly in connection with any scale what should be regarded as the lower borderline for the mature. Numerous examiners, however, in reporting their results, concluded that if the feeble-minded tested as high as XII then adults who tested XII were feeble-minded. They were somewhat encouraged in this fallacy by the fact that the 1908 scales suggested three years of retardation as an indication of feeble-mindedness, and the highest age-group of tests was soon shifted to fifteen years.

The trouble seems to have been that early workers failed to recognize that some of the feeble-minded in institutions, the purely conative cases, have passable capacity so far as the brief intellectual tests are concerned. To determine scientifically what is the borderline, we should study randomly selected groups from the general population and determine the positions on the scale below which practically all are socially unfit. Or, as Wallin has suggested, we should find out the degree of tested ability necessary for survival in simple occupations that are afforded by society (216, p. 224). These positions can only be checked by finding the conditions in institutions or special classes. They cannot be determined by tests of these abnormal groups alone. Besides the confusion arising from these feeble-minded who are primarily unstable or inert, but with passable intellects, reasoning from the statistics on abnormal groups merely repeats a common fallacy. The fact that some inmates of institutions test XII does not let us know how many outside the institutions who test XII actually survive in society.

The randomly selected groups of children on which Binet tried out his tests were so ridiculously small that he continually cautioned against adopting his suggestions as to borderlines as anything but tentative. For judging the borderline for the mature there were no test results which had not been seriously affected by the methods of selecting the groups, so we collected the data on this random group of Minneapolis 15-year-olds. I trust that this will make any examiner more careful about assuming that adults testing XI are clearly unable to survive socially, unless he is ready to claim that 10% of the general population are unfit socially.

It is to be noted that, taken literally, the description of the American Association is not in terms of the Binet scale, but of the mental development of a normal child of twelve years, although the framers of the resolution undoubtedly had the Binet scale of mental ages in mind. It was soon found that the tests for the older ages in the Binet 1908 scale were too difficult for the places assigned them. This is certainly true with the tests for twelve years and probably with those for eleven. This evidence is assembled in Table IV. The combined results should be used only with great caution since the methods of the investigators differed in detail and the groups were differently chosen. In the groups of children which Bobertag and Bloch and Preiss tested, there had been eliminated some of those who were backward in school, while Goddard's group did not include the best 12-year-olds.

TABLE IV.

Results with the Binet Tests for Mental Ages XI and XII

(1908 Series)

Binet and Simon. L'Annee Psychol., 1908, 14: 1911, 17: 145-200.

Bloch and Preiss. Zeits. f. angew. Psychol., 1912, 6: 539-547.

Bobertag. Zeits. f. angew. Psychol., 1912, 6: 495-538.

Dougherty. J. of Educ. Psychol., 1913, 4: 338-352.

Goddard. Ped. Sem., 1911, 18: 232-259.

Johnston. J. of Exper. Ped., 1911, 1: 24-31.

Terman and Childs. J. of Educ. Psychol., 1912, 3: (Feb.-May).

Rogers and McIntyre. Brit. J. of Psychol., 1914, 7: 265-299.

Each of the studies indicated in the table, except that of Bloch and Preiss, gives evidence that the XII-year tests are too difficult for 12-year-old children. Moreover, we find that in the 1911 revision of their scale Binet and Simon advanced their 1908 XII-year tests to test-age XV and four out of the five XI-year tests to test-age XII. Passing the XII-year (1908) tests would, therefore, seem to bring a child above the upper limit of feeble-mindedness as defined even by the American Association for the Study of Feeble-mindedness, since it means more than the intelligence of a child of 12.

Goddard still adhered to this borderline of the American Association in 1914 in his work on Feeble-Mindedness. He says: “We have practically agreed to call all persons feeble-minded who do not arrive at an intelligence higher than that of the twelve year old normal child” (p. 573). In the same year Schwegler's “Teachers' Manual” for the use of the Binet scale says that a person who tests XII is a moron if mature ([180]). Since the evidence of Table IV indicates that 75% of the twelve-year-olds do not test above XI, even those who adhere to the high limit of the intelligence of a 12-year-old should have required an adult to test XI on the Binet scale in order to show deficiency.

In 1911 we find Wallin writing, regarding the 1908 tests, “it is a question whether the line of feeble-mindedness should not be drawn between eleven and twelve instead of between twelve and thirteen.... A number of our twelve-year-olds are certainly very slightly, if at all, feeble-minded” ([210]). Jennings and Hallock ([31]) and Morrow and Bridgman ([39]) in testing delinquents reported in 1911 and 1912 that they regarded those passing the tests for twelve years as socially fit. Chotzen ([31]) thinks that the two children in his group of pupils from a Hilfsschule who test ten and are three years or more retarded are not feeble-minded. Davis thinks that those “showing mentality from ten to twelve years” may possibly not be called mentally defective (133, p. 187).

In 1915 the editors of the magazine “Ungraded” in their recommendations regarding the use of the Binet scale say “a mental age of 10 or above is not necessarily indicative of feeble-mindedness, regardless of how old the examinee may be” (66, p. 7). In the same year Kohs, in reporting the examinations of 335 consecutive cases at the Chicago House of Correction, says: “We find normality to range within the limits 12² and 10⁴ and feeble-mindedness not to extend above the limit 11². In other words, none of our cases testing 11³ or over was found, with the aid of other confirmatory data, to be mentally defective. None of our cases testing 10³ or below was found to be normal. Of those testing between 10⁴ and 11², our borderline cases, a little less than half were found normal, and somewhat more than half were found feeble-minded” ([33]). His exponents here refer to number of tests and not to tenths of a test-year. Hinckley ([182]) reports examinations with the Binet 1911 scale on 200 consecutive cases at the New York Clearing House for Mental Defectives which show that with these suspected cases, which were from 13 to 43 years of age, seven-eighths tested X or below. Referring to adults, Wallin states that he has “provisionally placed the limen somewhere between the ages of IX and X” ([215]). Dr. Mabel Fernald at the Bedford Reformatory laboratory said in 1917, “many of us for some time have been using a standard that only those who rank below ten years mentally can be called feeble-minded with certainty” ([16]). The reader should also see the admirable review and discussion of the borderlines on the Binet scale in Chap. II of Wallin's Problems of Subnormality. Two descriptions of the scale borderlines in books on mental testing which appeared in 1917 are of interest. In his Clinical Studies in Feeble-Mindedness (p. 76), E. A. Doll says:

“By the Binet-Simon method feeble-mindedness is almost always (probably more than 95 times in a hundred) an accurately safe diagnosis when the person examined exhibits a mental age under 12 years with an absolute retardation of more than three years, or a relative retardation of more than 25 per cent.”

N. J. Melville, in his Standard Method of Testing Juvenile Mentality (p. 10), says:

“Conservative estimates today place the upper limit of feeble-mindedness at least in a legal sense at Binet age ten; others place it at Binet age eleven.... A Binet age score below eleven when accompanied by a sub-age (retardation) of more than three years is usually indicative of serious mental deficiency. Even when accompanied by a slight sub-age score, a Binet age score below eleven may be indicative of potential mental deficiency when the test record reveals a Binet base that is six or more years below the life age.”

In 1916 the new Stanford scale appeared and its tests are arranged so that approximately 50% of each age instead of 75%, test at age or above. Even with this lowering of the scale units, Dr. Terman describes his borderline for “definite feeble-mindedness” as below an intelligence quotient of 70. This would mean for his 16-year-old mature borderline a mental age on this scale of XI.2. We have no means of determining to what positions these points on the Stanford scale would correspond on the 1908 or 1911 Binet scales. Dr. Terman says “the adult moron would range from about 7-year to 11-year intelligence” ([57]). Apparently also referring to the Stanford scale, the physicians at the Pediatric Clinic of that university agree with this borderline and say: “morons are such high grade feeble-minded as never at any age acquire a mental age greater than 10 years” ([169]). That there is still need for more caution is evidenced by the statement of a prominent clinician in 1916 that “cases prove ultimately to be feeble-minded since they never develop beyond 12 years intelligence” ([135]).

Most interesting perhaps is the fact that Binet and Simon themselves, the collaborators who first formulated the scale for measuring intelligence by mental ages, after their years of experience with the tests came, by rule of thumb, to regard IX as the highest level reached by those testing deficient. Dr. Simon stated the borderline for the mature in this way in a paper read in England in 1914 and published the next year. He said:

“Provisionally it might be proposed to fix at 9 years the upper level of mental debility.... We have reason to think that a development equivalent to the normal average at 9 years of age is the minimum below which the individual is incapable of getting along without tutelage in the conditions of modern life. A certain number of facts suggest this view and are mutually confirmatory. Nine years is the intellectual level found in the lowest class of domestic servants, in those who are just on the border of a possible existence in economic independence; it is, on the other hand, the highest level met with in general paralytics who come under asylum care on account of their dementia; so long as a general paralytic, setting aside any question of active delirious symptoms, has not fallen below the intellectual level of 9 years, he can keep at liberty; once he has reached that level, he ceases to be able to live in society. And lastly, when we examine in our asylums cases of congenital defect, brought under care for the sole reason that their intelligence would not admit of their adapting themselves sufficiently to the complex conditions of life, we find that amongst the most highly developed the level of intelligence does not exceed that of a normal child of 9 years of age” ([182]).

In connection with their 1911 revision of the scale Binet and Simon had stated that among 20 adults in a hospital where custodial care was provided for the deficient “we found that the best endowed did not surpass the normal level of nine or ten years, and in consequence our measuring scale furnished us something by which to raise before them a barrier that they could not pass” (79, p. 267). They, however, then expressed complete reserve as to the application of this criterion to subjects in different environments on their presumption that deficiency for the laboring class is different from that for other classes in the population.

The Germans seem to have early recognized a lower borderline for the mature than we did in this country for we find Chotzen saying in 1912 that he agreed with Binet's finding that “idiots do not rise above a mental age of three, imbeciles not over seven, and debile not over ten” (89, p. 494). Stern also quotes Binet as declaring that the moron does not progress beyond the mental age of nine (188, p. 70).

The tendency of interpretation indicated by these studies is plainly to lower the borderline for passable mature intellects until it approaches the limits which the percentage definition suggests as reasonable from our available evidence. The percentage plan thus confirms the borderline that has been approached gradually by hit or miss methods. An adult testing IX is presumed deficient, while one testing X is in an uncertain zone. The numerous studies of delinquents which have regarded adults who tested XI and even XII as deficient have seriously overestimated the problem of the deficient delinquent, as we shall see in our later chapter on tested delinquents.

B. The Border Region for the Immature.

(a) For the Binet 1908 Scale.

In attempting to adapt the percentage method of description to the border region for the immature, it is essential that the tests shall have been tried out on randomly selected groups. Neither teachers nor the examiner should pick out children to be tested, if we are to know much about the region of lowest intellects. While Bobertag's method of choosing typical groups by balancing those backward in school by those advanced, is serviceable for his purpose of determining norms, the personal element of choice involved makes the results thus obtained almost useless in determining the lower limit of ability.

In regard to the diagnosis of intellectual deficiency by the Binet 1908 or 1911 scales, we know much more about the interpretation of results obtained with the 1908 scale than with the 1911 scale. The 1908 scale was therefore used for our examinations of juvenile delinquents. The best available data on which to base a description of the borderline for the immature is that collected by Goddard ([119]). He says that he “arranged to test the entire school population of one complete school system. This system includes about five thousand population within a small city and as many more outside, so that we have, city and country, a school population of about two thousand children.... In the seventh and eighth grammar grades and the high school, the children were tested in groups.” Since only the first six grades were tested individually and only these results are published in sufficient detail to be available, we shall confine this account to the school children below the seventh grade. It must be remembered that any children of the idiot class and possibly some of the low imbeciles would not be included in his figures for they would probably have been excused from school attendance. In a small rural community it is not likely that these would be numerous enough to change the rough borderline materially. We thus have a fairly random group for a small town and its environs.

Since we cannot use Goddard's results for our purpose above the sixth grade, it is plain that we would not sufficiently approach a random distribution for any age above 11 years. In Minneapolis, for example, a recent census showed 28% of the public school children 12 years of age are in the seventh grade or above, while 6% of the better eleven-year-olds would be excluded by including only those below the seventh grade. We have therefore omitted from our calculations all of Goddard's results for children above eleven years of age as too unreliable for purposes of percentage estimations. Even his eleven-year-olds may be affected.

Although it is not clear in the published reports whether the nearest or last birthday was used, Dr. Goddard has informed me that his table shows the results for ages at the last birthday. A child is regarded as six until he has reached his seventh birthday, as is customary. Throughout this book I have followed this method of using age to mean age at last birthday, or avowed age. This is in conformity with the common use of age and with general anthropometric practise. It is less confusing and less subject to mistake or errors of record. On the whole, I believe that in statistical work avowed age is preferable to nearest age.

TABLE V.

Percentages of Mentally Retarded Children Tested with the 1908 Binet Scale. (From Goddard's Table.)

In the accompanying Table V Goddard's results are arranged so as to show the percentages at each life-age retarded two or more, three or more, four or more, and five or more years according to the Binet 1908 scale. The heavy black line indicates the upper borderline of the doubtful group according to our interpretation. In spite of irregularities, due mainly to insufficient numbers, the trend of the table is fairly plain. The column of percentages two or more years retarded and to the left of the heavy line suggests that the break comes at ten years of age. Using our tentative criterion of 0.5% presumably deficient and the next 1.0% uncertain intellectually, the outcome of this analysis is a rather striking demonstration of the feasibility of the percentage procedure even when the groups examined at each age are only composed of about 200 cases. I have preferred to take the empirical data at the lower extreme of each age distribution instead of projecting the tail of a smoothed distribution curve for each age.

Until better data are available we have adopted in practise, as a result of the study of this table, the procedure of considering any child who is ten years of age or over as testing of doubtful capacity if he is four or more years retarded below his chronological age, three or more years retarded if he is under ten years of age. If he shows one additional year of retardation we consider, in the absence of some other explanation of his retardation, that he is presumably intellectually deficient enough to justify a recommendation of isolation. Of course no such recommendation should be made without a complete medical examination, a full knowledge of the history of the case and a checking of the record by further tests at different times when there is any suspicion that the child has not done as well as he might under other conditions.

The fact that we have no data on random groups 12, 13 and 14 years of age leaves a gap which may mean that our criterion of 5 years retardation for presumable deficiency at these ages is too small. It is possible that the shift to 6 years retardation should be made before 15 years, which is the position where our criterion for the borderline for the mature automatically makes the shift. We say a 15-year-old testing X is above the group presumably deficient as he has entered the “doubtful” adult class.

It is also to be remembered that the standard error expected from the results of samples as small as these is 0.5% when the sample is 200 and 0.7% when it is 100. The limits thus might easily shift a year. The suggested borderlines for the immature can at best be regarded only as the most likely under the meager evidence available.

Whether the borderlines for deficiency on the Binet scale should be described in terms of years of retardation is doubtful except, as in this case, for practical convenience. It is certainly only a rough indication of the borderlines. When this method has not been followed the most common practise is to use some form of Stern's “intelligence quotient.” An extended discussion of this question is reserved for Part II of this book, to which the reader is referred. It need only be said here that the percentage procedure adapts itself to either method of description. Since the designation of the limits must be very rough until we have much further information from tests upon unselected groups, we have adopted the common method of description in terms of years of retardation, since it seems to afford for the 1908 scale the simplest expression of the borderline until the tests have been much improved. It happens that the empirical results for 5 years of age and over lend themselves to designating the lowest percentages in terms of years of retardation with only a single shift at 9 years of age. An equally accurate designation by the intelligence quotient would be quite complicated if it were adapted equally well to the different life-ages.

The fact that the Binet mental ages do not signify corresponding norms at each age has been frequently pointed out ([200]). Moreover it is probable that one year of retardation on the scale means a different thing at different chronological ages. With the new Stanford form of the scale, for example, “a year of deviation at age 6 is exactly equivalent to a deviation of 18 months at age 9, and to 2 years at age 12, etc.” ([197]) when measured in terms of the deviation in ability at these ages. This variation does not interfere, however, with our use of the “years of retardation” merely as a short method for describing empirically the positions on the scale which roughly and conservatively designate the same percentages of children of low ability at various ages. Besides its convenience in this respect, there is no question but that such a description does help better than a quotient to convince the public of the seriousness of the deficiency.

A more serious theoretical objection to describing the borderline for the immature in terms of years of retardation is that, when one changes from three to four years of retardation, it is clear that a moron who tests VI at 9 years of age would be supposed to be still only VI at 10 years in order to remain below the borderline, while it is known that there is some, albeit a small, amount of progress made by the higher class deficients at these ages. In the crude state in which the Binet scale still remains, however, we have preferred to waive these theoretical objections in favor of the prevalent custom which has the advantages of simplicity, practical convenience, popular significance and, in this case, equal accuracy.