What Is Intelligence?

AN immature science often breeds premature conclusions. Psychology is distinctly an immature science. Twenty-five years ago it was still considered a part of philosophy, and only since then has it achieved the status of what, in university circles, would be called an independent discipline. Its progress toward becoming a genuine science has been rapid, and the nature of its achievements such as to engage a lively and universal interest. The human mind is always a fascinating subject for speculation; but the development of mental tests, probably the most notable achievement of the new psychology, has appealed to popular imagination as few scientific achievements have done.

With all respect for merit, Applied Psychology is to-day the Jackie Coogan of the scientific world. Such sudden popularity is rarely conducive to deliberate scientific judgments. In this case it has undoubtedly led some psychologists to make claims for their work which the criticisms of other psychologists would have compelled them, in time, to abandon.

But scientific investigation and analysis move slowly, whereas popular interest, when aroused, moves quickly. The journalists and writers through whom this interest has expressed itself have been quick to exploit the results and theories advanced by psychologists. Their zeal, in most instances, has been greater than their discrimination. Even so, they have performed a genuine service by pushing the implications of these theories to their logical limits and by showing their radical effects in the fields of sociology, racial psychology, and education.

During this discussion, the increasing number of psychologists who disagree with some of the claims made for mental tests has remained inarticulate. One of this number may now be allowed to present his analysis, on the ground that this is, for once, the psychological moment.


Probably the most widely advertised and most vigorously denounced assertion in regard to mental tests is that based on the results of the army intelligence tests, according to which less than fifteen per cent of all those tested were of very superior and superior intelligence. From these results it has frequently been inferred that only fifteen per cent of the population of the United States are superior in intelligence. It is surprising that these claims should even be questioned; for, regardless of the validity of intelligence tests, it must be obvious to any person that a certain proportion of the people in any group are superior in intelligence to the rest.

Without even using a yardstick, we can say that five per cent of a population are superior in height to the other ninety-five per cent, and that fifteen per cent are taller than the remaining eighty-five per cent. The average height might be five feet or seven feet, and still this statement would be true.

Just so, without the use of an intelligence scale, we know that five per cent of all people are superior in intelligence to the other ninety-five, that ten per cent are more intelligent than the other ninety per cent, and that ninety-nine percentare superior in intelligence to the remaining one per cent .

This again holds true whether the average level of intelligence is high or low.

In order, however, to select the five, or fifteen, per cent whose intelligence is superior to that of the rest, it is necessary to apply a yardstick, or a device for measuring the intelligence of the individuals who compose the group. The intelligence tests represent an attempt to provide such a device. Their use has made it possible to arrange individuals in the order of their ability as measured by this scale, and to say that all those above a certain point on the scale are superior to those below that point.

Thus far the use of intelligence tests reveals nothing new or startling. Any test whatsoever, whether of height, weight, spelling, or speed in copying a letter, if uniformly applied, will arrange all those tested in a definite order, or according to certain levels. But though we admit the validity of an intelligence test as a means of arranging people in the order of the ability they manifest in meeting that test, by what authority can we claim that such a test is a measure of intelligence? How do we know that we are testing this particular quality and what do we mean by intelligence in the first place?


The question, what is intelligence, will puzzle almost any psychologist, because no psychologist has ever succeeded in giving a satisfactory answer. Indeed, the history of psychology is littered with inconclusive controversies over the meaning of this term. Intelligence has been variously defined as the ability to learn, to profit by experience, to adapt one’s self to the environment, to solve new problems, to benefit by trial and error. True as they may be, these definitions add little to our understanding of intelligence. They are no more enlightening than the definition given by a pupil who said, ‘Intelligence is that faculty of man, that divine spark as it were, which enables him to rise superior to his environment.’

Baffled in the attempt to define intelligence, many psychologists have implicitly accepted its existence as an inherited force of some kind, a spark divine or mundane according to one’s personal belief, and are now trying to measure the degree in which individuals possess it.

This procedure again reveals nothing strange, any more than does the attempt to measure electricity, a force which no one has yet defined. The attempts to measure electricity were based upon careful experiments with its effects.

In like manner, the attempts to measure intelligence are based upon numerous experiments with the responses of children and adults to certain mental problems. The experiments from which most of the claims regarding the significance of intelligence tests are derived were conducted under the auspices of the Leland Stanford University by Professor Lewis M. Terman and his associates, and resulted in the wellknown Stanford Revision of the BinetSimon Intelligence Tests.

The Stanford Revision consists of groups of mental problems, one group for each step in mental age, and may be illustrated by the tests assigned to designate the mental age of ten.

1. Defining correctly thirty words of increasing difficulty; such as orange, health, plumbing, treasury.

2. Pointing out the absurdity in four out of five sentences such as this: An engineer said that the more cars he had on his train, the faster he could go.

3. Reproducing on paper two designs which have been shown for ten seconds.

4. Reading a sentence of fifty-three words and recalling eight of the facts contained therein.

5. Answering correctly two out of three sentences such as the following: Why should we judge a person more by his actions than by his words?

6. Naming at random sixty words in three minutes.

A person who passes this group of tests is credited with the mental age of ten. He is also credited with from two to four months for each problem which he does successfully in the groups for succeeding ages, and the sum total of his credits determines his mental age. The I. Q., or intelligence quotient, is obtained by dividing his mental age by his chronological age. Thus, a person twelve years old whose work in the tests entitles him to a mental age of six has an intelligence quotient of .50 (6÷12 = .50), and a person ten years old who tests at a mental age of five has an I. Q. of .50 also (5÷10 = .50). A child of eight years who tests at a mental age of nine has an I. Q. of 1.12 (9÷8 = 1.12).

If we bear in mind possible errors in giving and marking these tests, there can be no objection to their validity as measures of certain mental abilities. But upon what grounds can they be called measures of mental age and intelligence?

The answer to this question, as given by the psychologists who make this claim, lies in the method by which they constructed their scale. ‘The guiding principle,’ says Professor Terman, ‘was to secure an arrangement of the tests and a standard of scoring which would cause the median mental age of the unselected children of each age-group to coincide with the median chronological age. That is, a correct scale must cause the average child of five years to test exactly at five, the average child of six to test exactly at six, and so forth.’

In other words, the mental age was set, arbitrarily, on the basis of what the average individual at a given chronological age could do with a given set of problems. And the problems assigned to each mental age were selected in such a way that this arbitrary condition should be met.

This in itself is a perfectly legitimate procedure, common to all scientific research. The inches on a yardstick and the decimetres on a metre-stick, as well as the degrees on a thermometer, Centigrade or Fahrenheit, are arbitrary units. When we apply these arbitrary units in measuring distance or temperature, their significance is generally understood. For accuracy’s sake, the physicist, in stating the degree of temperature, adds also the letter F or C to indicate which arbitrary unit he is measuring by.

Now, in the case of the Stanford Revision, the units of measurement were arbitrarily selected on the basis of experiments with children and adults themselves arbitrarily chosen.

For the mental ages of from three to fourteen this intelligence scale was standardized from the results of tests given to 1305 California schoolchildren. These children, according to Professor Terman, represented an unselected or sample group; but he tells us also that, in the treatment of the final results, all children of foreign-born parents, about four hundred in number, were eliminated. The scale, therefore, actually represents the performance of 905 children, selected to the extent that all of them were in school at the time and, without exception, of native parentage. Consequently, wherever this scale is applied, it measures the abilities of those tested in terms of the abilities of this original group.

For example, when testing children in the schools of New York City, we are measuring them in terms of what 905 children of native-born parents in the schools of California have done. And when we say that children in one part of the country are less intelligent than those in another section, we should think of intelligence solely as defined by this arbitrary scale.

This again, is a perfectly legitimate procedure from a scientific point of view, assuming that we bear in mind the exact significance of what we are doing, and that we refrain from drawing inferences about intelligence which are not implied in the technique itself. But even though this procedure is scientifically sound, there is the question of how it works in actual practice. Can a scale based upon so small a group of selected subjects be used successfully in measuring children in all parts of the country?

The answer to this question is to be found in the results obtained in thousands of schools, in every state in the Union, from hundreds of thousands of children to whom the tests have been given. Obviously, the results could not agree perfectly with those originally obtained with the schoolchildren of California; but they were similar enough to indicate that the scale had a very wide applicability. For example, children of a certain age in the schools of New York City, or Dayton, Ohio, reached about the same mental age in the tests as that reached by the children in the schools of California.

Walter Lippmann, in his penetrating articles on intelligence tests, refers to the tests again and again as ‘puzzles’ and ‘stunts,’ and says in one connection that they may specially favor ‘the type of mind which is very apt in solving Sunday newspaper puzzles, or even in playing chess.’ Undoubtedly, there is an element of the stunt or puzzle in all intelligence tests, or, for that matter, in any mental problem which a group of individuals might be called upon to solve. An original problem in geometry is a clear-cut process for one student, but a twisting and elusive chase for another. The problems and questions in the Stanford scale were selected with the express purpose of reducing the stunt or puzzle element to a minimum.

The degree in which this purpose was achieved is demonstrated beyond question by the surprisingly uniform results obtained with the scale in all parts of the country. These results could not have been obtained with a collection of stunts and puzzles which, regardless of whether or not they were measures of intelligence, did not involve mental activities of a fundamental and vary common type.

From this point of view alone, the Stanford Revision should be regarded as a scientific achievement of great note — though only those experienced in the intricacies of standardizing such tests are likely to accord it the appreciation it deserves.

In the face of the inertia which most radical innovations encounter, these tests have won for themselves an important place in the educational system. They have been adopted by thousands of schools as an aid in discovering children whose mental status is such that they should be placed in a higher or lower grade. The classifications which they have made possible, whether right or wrong, have tended to upset the complacency of teachers and educators everywhere with the traditional methods of grading.

Indeed, these tests have given the educational world, for the first time, a universal language in terms of which all sorts of stimulating and irritating comparisons between the educational and mental status of children in schools all over the country can be made.


In view of these achievements, I have no hesitation in expressing the opinion that Professor Terman and the psychologists responsible for the development of intelligence tests have made the greatest single contribution to the field of education in our time. Just because their work has claims to such greatness, it is unfortunate that they should saddle it with such statements as the following: —

That the Stanford Revision and similar scales are measures of native or inherited intelligence and not of education.

That intelligence as measured by these tests is affected little or not at all by education.

That the native intelligence of different races and different social groups within the same race can be compared on the basis of these tests.

That the intelligence of most people does not develop far beyond the mental age of fourteen or fifteen.

Let us accept, for the moment, the truth of these statements, and observe their effect upon the interpretations to be made from the application of the intelligence scale. If a fourth-grade teacher tests Johnny Smith, who is twelve years old and should be In the sixth grade, and finds that his mental age, according to the scale, is only ten, it means that he is lacking in native intelligence, not that he has lacked the proper education. Consequently the teachers, the school, and the community may absolve themselves from blame for the fact that Johnny is two years behind in his school attainments, and lay the responsibility upon the Creator, or biological forces which endowed him with less intelligence than the average child.

Or if the children in a rural school, where one teacher has three or four grades, register a lower I. Q. than the children of like ages in the schools of Boston, it is not because the educational facilities of the latter are superior but because the intelligence of the former is inferior.

The lower I. Q. of Negro children in the South as compared with negro children in the North must be attributed to a lesser inheritance, not to more meagre educational opportunities. As a rule, children from the homes of families well up in the social and economic scale have a higher I. Q. than children from families less fortunate in those respects.

This is due, not to a more favorable environment and the better educational advantages which parents of means can afford their children, but to the better heritage with which they endow their children at birth.

And when, as is usually the case, children of foreign-born parents have a lower I. Q. than children of native-born parents, it is not because the latter have the educational advantages of an English-speaking environment, but because the former come from races characterized by a lower level of inborn intelligence.

Whether these facts are true or not, the assumption that the scale measures inborn intelligence, independently of the effects of environment and education, tends to relieve the educational system from the responsibility for the mental attainments of its pupils. A child endowed with a certain degree of intelligence will attain a certain level of education, not because of the educational system, but in spite of it.

We have it in our power to improve the methods and standards of education, and the testing technique offers a valuable aid toward achieving this desirable end; but why go to all this trouble when the innate intelligence of those to be educated will not permit them to profit by these improvements?

‘It is quite commonly believed,’said Robert M. Yerkes in a recent issue of the Atlantic Monthly, ‘that intelligence increases with schooling. This, however, is flatly contradicted by the results of research, for it turns out that the main reason that intelligence status improves with years of schooling is the elimination of the less capable pupil. All along the line, from kindergarten to professional school, the less able and less fortunate in home conditions tend to drop out. Not more than fifty per cent of our population are capable of satisfactorily completing the work of a first-class high school. . . . Education, instead of increasing our intellectual capacity, merely develops and facilitates its use.'

Professor Terman and his followers would probably agree to this as a fair statement of the case. Indeed, the outstanding fact in the entire field of tests is the constant agreement between the educational status and the mental status.

Therefore our pessimistic view about the importance of education is probably beside the point.

For, even though education cannot give a boy any more intelligence than he was given by nature at birth, it can at least ‘develop and facilitate’ his ability to use that which he has.


Inborn intelligence and acquired facility in using it! The distinction called for here is the critical point in this whole doctrine of intelligence and its measurement. We may freely admit that the tests in question are measures of the intelligence which all individuals inherit in varying degrees. But common sense compels us to admit also that they measure, at the same time, the effects of education and environment.

The informal tests which we meet every day of our lives are tests of our native intelligence; but they are also tests of acquired facility. We solve our problems with what we have learned as well as with what nature has given us. Our responses spring from all that we are at the moment, beings in whom hereditary forces, physical nurture, the effects of education and environment, are blended into one. Our actions register like a man’s weight — so many pounds, regardless of whether he is two-thirds flesh or two-thirds bone.

The intelligence scale, like a weighing scale, registers a single result called the mental age; and this result is derived from all that the individual is at the time. In order to obtain an undiluted measure of native intelligence, it would be necessary to measure it at birth before the effects of environment and nurture had come into play. But the very nature of the tests we are discussing is such that they do not become effective until the child has learned to talk.

Dr. H. H. Goddard, in his lectures on Human Efficiency and Levels of Intelligence, makes the assertion that ‘intelligence is an inherited force, while knowledge is wholly acquired. Moreover, they are not to a large extent interdependent.’ And yet, no intelligence test has ever been devised which does not measure in terms of acquired knowledge. When we give such a test, we do not measure an abstract and independent force called intelligence, but a composite of the inborn forces of intellect and character and the many forces exerted by environment and education.

We must think of intelligence, therefore, as something which is not only inherited but developed.

The psychologist who believes that his tests measure inherited intelligence would say to this: Granted that these tests do not measure pure intelligence, but intelligence as developed by exterior forces, they nevertheless enable us to demonstrate a difference between that which is inherited and that which is acquired.

For example, if we apply the scale to children reared in exactly the same environment and under the same educational system, we find that they register different degrees of intelligence. Therefore the differences in their mental ages can be attributed only to differences in their mental endowment. This is a logical inference; but we cannot make this inference until it has been proved that the intelligence of the children in question has been developed under uniformly favorable conditions. The task of proving this involves many serious difficulties. How can we measure the environmental effects of different parents, of different social and economic levels? Even the same parents may constitute a more favorable environment for one of their children than for the other. Moreover, the first-born child in a family helps to create a different environment for the second child, and so on. In school, the same teachers and same studies may constitute a more favorable environment for one pupil than for another.

Conceivably we might, under laboratory conditions, establish for a group of children a uniformly favorable environment and, from its results, deduce the differences in their native endowment. In the meantime, we have been applying our tests to children and adults from every kind of environment and school, and drawing inferences in regard to their mental endowments. ‘That the children of superior social classes make a better showing in the tests,’ says Professor Terman, ‘is probably due, for the most part, to a superiority in original endowment.’ Possibly; but until the effects of a superior linguistic, social, and economic environment have been determined, such a statement remains a bare personal assumption.

We saw that the Stanford intelligence scale up to the age of fourteen was constructed on the basis of tests given to children of native-born parents in the California schools. They are, then, tests of native intelligence as developed by these schools.

If, on the basis of these tests, a similar group of American children in another community attains a lower mental age, shall we say that these children are less intelligent by nature, or shall we, perhaps, look for a difference in the activeness of the educational systems involved? The control of the latter is within our hands. The control of heredity, even if we could measure it independently, is at present practically impossible.

If the children of non-English-speaking foreign-born parents register, as is usually the case, a lower mental age than the children of native-born parents, must we infer that they come from a race which is inherently inferior, or shall we say that the development of their intelligence has been handicapped from birth, by a poor linguistic environment? ‘The vocabulary test,’says Professor Terman, ‘has a far higher value than any other single test of the scale. Used with children of Englishspeaking parents (with children whose home language is not English it is, of course, unreliable), it probably has a higher value than any three other tests in the scale. Our statistics show that in a large majority of cases the vocabulary test alone will give us an intelligence quotient within ten per cent of that secured by the entire scale.’

Professor Terman might go further, and say that the reliability of the entire scale depends upon the ability to understand and use the English language; that it is a test of intelligence in so far as intelligence has been developed by English-speaking institutions. The admission he makes does not prevent him and other psychologists from using this and similar tests, like the army Alpha test, as a criterion of the innate intelligence of different races and children from different social strata.

In order to overcome the difficulties arising from the use of the English language, some psychologists have devised non-verbal intelligence scales. The army Beta test, which gives directions by means of pantomime instead of by words, is an example. Of such tests it may be said that their results are not to be compared, except for statistical purposes, with the results of a test like the army Alpha or the Stanford Revision.

Intelligence, we have seen, is always measured in terms of how it has grown up. Before we can infer that any race, or any group in the same race, is inherently inferior to any other, we must be sure that every individual has had the advantages of an equally favorable social and economic environment and an equally effective educational process.

There is absolutely nothing in the technique of intelligence tests as applied so far, which warrants any comparison whatsoever between the inherent intelligence of various groups or races. All that we can say is that there is a difference in their scores, and that this difference may be due to any number of factors, of which native endowment is only one.

We have, in our south Appalachian states, over five million people of old American stock, who can neither read nor write. The young men from this group, judged by their scores in the Army tests, possess no more intelligence than the twelve-year-old children of foreign-born parents in the schools of New England. Shall we infer from this that a large proportion of our native Americans are by nature inferior even to the ‘inferior’ races, or shall we attribute the difference to unequal economic and educational opportunities ?

According to the statement by Dr. Yerkes, already quoted, the effects of education on levels of intelligence is only apparent, because all along the line those unable to benefit from further education drop out. Many of the illiterate Americans have never even entered school. Their intelligence has been neither stimulated nor arrested by contact with teachers. And who is so bold as to say that the chief reason for the low average intelligence of the people of the United States, as measured by these tests, is the fact that they have acquired all the education which their native intelligence will permit?


Thus far, we have confined ourselves chiefly to the question of measuring the intelligence of children up to fourteen years of age; but since the average adult intelligence is said to be approximately that of the average thirteen-to-fourteen-year-old child, we have not gone far afield in our analysis. There is some doubt among psychologists as to what the average mental age of our population really is. But according to the tests applied thus far, the majority of adults do seem to reach the limit of their intelligence at the age of sixteen or before. If this is true, the results of these tests indicate an extremely important characteristic about human intelligence. But is it true? Do these tests actually prove that a majority of us do not have more intelligence at the age of thirty or forty than at the age of sixteen?

Instead of analyzing the method by which these results are obtained, let us rather begin by an analysis of the conditions which made them possible. All children are born with varying capacities in varying degrees. Just what these variations are, we cannot say, since we have no means of measuring them at the time. Regardless of their original endowment, nearly all children are compelled to develop under the influence of a common language and a common school-system. They must acquire first a vocabulary and a command of sentence structure. Their intelligence in the grammar grades is subjected to a common discipline, consisting of such studies as reading, writing, arithmetic, geography, history, drawing. During the course of this discipline different children naturally display different degrees of proficiency, due either to differences in innate capacity, home environment, or the quality of their schools and teachers. Nevertheless, there is a genuine continuity and similarity in the attainments of most children under this discipline. It is this fact, above all others, which makes it possible for a scale like the Stanford Revision to measure pupils throughout the country in terms of a common test.

Let us compare the expression of our national intelligence to a tree, and let the trunk of that tree represent the common discipline which our language and institutions impose upon the operations of intelligence during early life.

Between the ages of fourteen and sixteen, about fifty per cent of all children leave the grammar grades before graduation and go to work. They branch off from the trunk and go into the stores, the factories, and commercial enterprises of every description. In these many occupations, their intelligence is subject to disciplines of many varieties, and their attainments become correspondingly unlike. Many remain drawers of water and hewers of wood, but a respectable number of them rise to positions of importance.

A certain proportion of the children who graduate from the grammar grades go to high school, and take either a commercial, academic, or technical course. Each of these courses involves different kinds of studies, in terms of which the intelligence of the pupils must express itself. Many of the pupils, either before or after graduation, take up occupations which again impose upon their intelligence restrictions and stimuli of widely varying kinds.

Some of those who graduate go to college, it may be to a liberal arts school, a normal school, an agricultural school, a school of business administration, or a scientific college for engineers — mechanical, civil, electrical, chemical. Once more we have a process of differentiation, the outcome of which is a collection of college graduates whose intelligence has become specialized in various degrees and in diverging directions.

Some college graduates specialize still further by taking up the study of medicine, the law, the ministry, or some special subject in a graduate school.

In short, the development of the attainments, if not of the intelligence, of our population takes place in a multitude of diverging directions in accordance with the exigencies and opportunities of our complicated civilization.

We have already pointed out that the Stanford scale, up to the mental age of fourteen, rests upon experiments with children in the schools of California. If the scale had been constructed in the schools of Michigan or Massachusetts, it would have served just as well: for the intelligence of children in these states as well as in most other states is subject to substantially the same discipline. Therefore their attainments lend themselves to measurement in terms of the same tests. But because this scale and similar scales fail to register an increase in intelligence much beyond the mental age of fourteen or sixteen, must we infer that the average person has reached the limit of his intelligence? Or is it more reasonable to say that our scale ceases to measure beyond a certain point, because thereafter the development of intelligence branches off in multitudinous directions?

The physicist and chemist apply accurate scales and measures in their study of the elements. When, beyond a certain point, their formulæ no longer explain the actions of the elements, they do not blame the elements, but endeavor to work out finer and more discriminating measures. In this way new elements are being constantly discovered.

Because our scale ceases to register an increase in average intelligence beyond the point at which most children have a common development, need we deny the further growth of intelligence, or shall we say that the nature of its growth is such that it can be measured only by additional tests of a finer and more discriminating type? Is it not reasonable to suppose that intelligence which develops in specific directions can be measured only by specific tests?

Attempts have been made to devise adequate tests of adult intelligence, and such tests have been successful when applied to homogeneous groups. College intelligence tests, for example, have successfully measured the capacity for making progress in college work, even though their reliability as a measure of intelligence, as defined by success in later life, is by no means certain.

A common test for measuring the mental age of unselected adults, however, has never been successful. And so long as the intelligence of the race is expended in a multitude of directions, — in the achievement of mechanical proficiency, artistic ability, professional skill, wealth, erudition, literary facility, the support of a family, with all the innumerable variations which these pursuits imply, — no such test will be adequate. Each adult reaches the limit of his intelligence, or his intellectual maturity in the field of his specific vocation or pursuit. Obviously we cannot, by selecting samples of intelligence in all these fields, construct a scale of tests which will be an adequate measure of mental age. Such a scale would fail to give due weight to the very factors that constitute the individual’s chief claim to mental distinction. To a person who makes assertions about the mental age of adults, the life of intelligence must look like a ramrod instead of like the tree Igdrasil, an infinite conjugation of the verb to do.

But, says the psychologist, you are now speaking of specific types of intelligence, which, naturally, cannot be measured by any one scale. By mental age we mean a stage of general intelligence, and no more. The distinction is an important one though somewhat belated; for in the comparisons so frequently made between the mental status of different races and different groups, the fact that general intelligence exists only because of a common nurture and a general educational system has been quite ignored. The tests may have been intended to measure general intelligence, but they have really been measuring in a wholesale way the effects of many specific conditions upon intelligence. When the psychologist admits the existence of degrees of specific intelligence, his assertions about the early maturity of intelligence and the low mental age of the average adult become meaningless; for if man reaches his full mental stature in terms of a specific achievement requiring specific intelligence, his mental age cannot be determined by any scale which measures only in a wholesale fashion.


Having said so much which must seem destructive, let us conclude by pointing out how valuable an instrument we possess in these tests if their application is properly understood. We shall begin by making a very simple suggestion, which will, nevertheless, make an enormous difference in our conception of the significance of these tests.

Let us think of the tests, not as measures of intelligence but as tests of attainment. The controversial claims that we have discussed arose not from the tests themselves, but out of the assumption that they were measures of intelligence as such. We know that this is not the case, but that they measure the mental habits to which, as a result of heredity and environment, we have attained.

If we think of these tests as measures of individual attainments, the scores of different racial groups will not compel us to infer that one race is inherently and permanently inferior to another. We shall simply say that, for any number of reasons, — heredity, economic circumstances, climatic conditions, linguistic difficulties, lack of education, — the intellectual attainments of one race are not equal to those of other races.

When comparing native adults of the South with natives of the North, we may take their scores at their face value and say, simply, that the attainments of one group as measured by certain tests are evidently superior to those of the other.

In comparing the scores of children from different social strata, we shall note differences in attainments but need not prejudice our further investigations by ascribing these differences to only one cause.

The army intelligence tests gave us an excellent survey of the attainments of a large section of the adult population. But to interpret these results solely in terms of innate intelligence is to close our eyes to the many other fruitful interpretations and investigations to which they might lead. As measures of what we have learned or, to satisfy the most meticulous, of how we have learned to use what we have learned, these scales are of inestimable value to educators, sociologists, and students of racial and group psychology.

If we describe tests like the Stanford Revision as tests, not of general intelligence but of common attainments, their controversial impedimenta will drop off and their intrinsic value suffer not the slightest impairment. Indeed, their practical worth will be enhanced; for, when these tests show differences in the scores of individual children, between groups of children in different communities, and between children of different racial and social environments, we shall not naïvely ascribe these differences to a mysterious factor, heredity, but concern ourselves equally with the many other factors which may have contributed to the result.

Used in this way, such scales are a powerful instrument in helping and stimulating the individual child to attain his fullest development, and in bringing the entire educational system to a more highly uniform level of effectiveness.

Among people who would govern themselves, general intelligence or a certain level of common attainment is the primary factor in the success of their common enterprise. Moreover, a civilization which, like the present, is becoming rapidly more intricate and involved, must evolve also a compensating rise in the level of general wisdom. Now, when we say that the mental age or native intelligence of the American adult population averages between thirteen and fifteen years, it is not only scientifically untrue but extremely irritating. Such a statement arouses widespread antagonism where general coöperation is most to be desired.

However, if we say that the level of common attainments is no higher than that of the average fourteen-yearold school child, our statement will seem not only reasonable but conservative. We recognize the inadequacy of our educational system. We know that large numbers of foreign-born and native adults have had little or no education. We appreciate the economic and legislative conditions which encourage many children to begin working at an early age. The general tendency toward premature and extreme specialization is a well-known phenomenon. All these factors and many others, besides inherited capacity, contribute to a low level of common attainment.

In calling attention to this fact, the tests we have discussed constitute a contribution of inestimable value. Assuming that our system of commonschool education is fundamentally sound, psychologists have provided an instrument which will not only help to point out its inequalities but help to elevate its general level. When a higher level of economic independence and common education has been achieved, then, also, will our tests register a higher level of common attainment.