Human efficiency and levels of intelligence, lectures delivered at Princeton University April 7,8,10,11, 1919.

Front matter

AND

IVELS OF INTELLIGENCE

HENRY HERBERT GODDARD

Preface

Without some word of explanation the reader might judge that the author of this book thought that intelligence was the sole determiner of human conduct. Such a view is of course inconsistent with the most obvious facts.

It happens however, that in the solution of this problem of human efficiency, we are just at present better equipped to evaluate the part intelligence plays, than any other of the psychological factors. It therefore seems worth while to solve our problem in terms of intelligence as though it were the only variable. The other unknown quantities may be considered when the part they play is better understood.

Let us solve our equation for x now and leave y and z for later consideration when we shall know as much about emotion and temperament as we now know about intelligence.

If mental level plays anything like the role it seems to, and if in each human being it is the fixed quantity that some believe it is, then it is no v: PREFACE

useless speculation that tries to see what would happen if society were organized so as to recognize and make use of the doctrine of mental levels.

Moreover if the views set forth in these lectures are in the main sound then it is quite possible to restate practically all of our social problems in terms of mental level.

For example, what could be done with labor and wages ? Suppose we say men should be paid first according to their intelligence; and second according to their labor: e.g., "D" men are worth and should receive "D" wages; C men C wages (which are higher), etc. If a certain job requires D intelligence, D men should be employed at D wages. If there are not enough D men, C men must be employed at C wages. And it may be relied upon that they will be worth the difference because of their greater intelligence.

If, of two jobs each requiring D intelligence, one is more agreeable than the other and hence draws all the D men, the conditions must be evened up as far as possible by changing hours, etc., and then by increasing the pay for the less desirable job. A little experimenting would equalize the two jobs so that all would be satisfied. Doubtless other adjustments would be found necessary. But the great advantage of

PREFACE vii

having every man doing work on his own mental level would prove fundamental.

Testing intelligence is no longer an experiment or of doubted value. It is fast becoming an exact science.

The facts revealed by the army tests cannot be ignored. Greater efficiency, we are always working for. Can these new facts be used to increase our efficiency? No question! We only await the Human Engineer who will undertake the work.

It is hoped that the consideration of the topics of these lectures will help prepare the way for greater social efficiency.

Introduction

The topic of mental levels or "levels of intelligence" has been chosen for these lectures because while the subject is not altogether new it seems that there are phases of it that have not been dwelt upon but which enable us to look at some of the present day problems from a new angle, and suggest solutions different from any usually discussed.

Stated in its boldest form our thesis is that the chief determiner of human conduct is a unitary mental process which we call intelligence: that this process is conditioned by a nervous mechanism that is inborn : that the degree of efficiency to be attained by that nervous mechanism and the consequent grade of intelligence or mental level for each individual is determined by the kind of chromosomes that come together with the union of the germ cells : that it is but little affected by any later influence except such serious accidents as may destroy part of the mechanism.

As a consequence any attempt at social adjustment which fails to take into account the determining character of the intelligence and its unalterable grade in each individual is illogical and inefficient.

MENTAL LEVELS

In one sense the doctrine of mental levels may be said to have had a lowly origin. On June 10th, 1903, Earl Barnes in concluding an address before the Corporation of The Vineland Training School for Feeble-Minded Girls and Boys, said: "To me Vineland is a human laboratory and a garden where unfortunate children are cared for, protected and loved while they unconsciously whisper to us syllable by syllable the secret of the soul's growth. It may very well be that the most ignorant shall teach us most."

In October 1904 the Minister of Public Instruction of Paris named a Commission which was charged with the "Study of Measures to be taken, Showing the Benefits of Instruction for Defective Children." This Commission decided that no child suspected of retardation should be eliminated from the ordinary school and admitted into a special class without first being subjected to a pedagogical and medical examination from which it could be certified that because of the state of his intelligence he was unable to profit in average measure from the instruction given in the ordinary school. But how the examination of each child should be made the Commission felt under no obligation to decide. To one member of that Commission, however, it seemed extremely useful to furnish a guide for future Commission examinations. That member was Alfred Binet. He felt strongly the need of a scientific method of determining what children needed this special treatment. He says, ' To be a member of a special class can never be a mark of distinction, and such as do not merit it must be spared the record." With this feeling Binet set to work upon the problem devoting the energy of his marvelous intellect and a large part of his time for approximately seven years to the developing and perfecting of a measuring scale for intelligence.

In 1906 the Vineland Laboratory was opened for the psychological study of feeble-mindedness. Those who are especially interested in the origin and evolution of ideas may be interested to ponder over the problem of how there should originate in two nations widely separated, different in language, and without collusion or suggestion from one to the other, the same idea though motivated by very different purposes. The Frenchman having the very definite and practical objective of determining who were the children who needed special education. The American having a vague conception that these same defectives might "unconsciously whisper to us syllable by syllable the secret of the soul's growth, and, thus, the most ignorant teach us most."

It was not long, of course, until these two streams of independent origin flowed together and out of them has grown the theory of mental levels.

It is often easy after a theoiy has been scientifically demonstrated to discover that there is nothing new about it. We have accepted and used it for long only under a different name, or without realizing its far-reaching significance. It is certainly not new to declare that a two-year old child is at a higher mental level than a one-year old. A child of ten is of higher intellectual development than one of six; and so far, it is true there is nothing new in the theory of mental levels. Throughout childhood the human being rises to an ever higher level of intelligence, but beyond this we had not gone, perhaps never would have gone had not the genius of a Binet given us the means of extending the principle. As so often happens in human affairs it is the part that is just beyond the obvious that proves to be of the utmost value. When gold was discovered in the Black Hills it was not long until the visible supply was exhausted, and at that time it was little realized that the rock, which to the placer miner was of no use, would one day furnish the material for the most profitable mining operation in the world.

It is a matter of every-day observation, as already stated, that children as they grow rise to a higher and higher level of intelligence. But two facts were unappreciated and even yet are so little recognized as to make the whole matter "a theory" in the minds of most. These two facts are: First that the intellectual development is largely independent of what we call learning or knowledge ; and second that not all develop to the highest level, or even near to it; many stop at some one of the lower levels of childhood. To produce the evidence for these facts and to draw some of the far-reaching conclusions therefrom is now our task.

That we may approach the problem with unbiased minds it will be well to first remove some of the obstacles. First let us state the theory more succinctly than we have yet done. The theory of mental levels holds that every human being comes into the world with a potentiality for mental development that will carry him just so far and that barring those accidents that may stop a person from reaching the development which would have been normal to him, nothing can, to any great extent, effect the mental level to which he will finally attain. Why is this view hard to accept?

Probably the first and most important reason is that we have generally confused intelligence with knowledge. Having no way to evaluate either one we have been lost in the intricacies and confusion results. At this point I should like to define each one but unfortunately we are unable to. We do not know what intelligence is and it is doubtful if we even know What knowledge is. This however need not frighten us since man works with and makes use of many things which he cannot define. For example electricity, which we can measure, control and use, but the exact nature of which has never yet been ascertained. We may point out that intelligence is an inherited force while knowledge is wholly acquired. Moreover they are not to a large extent inter-dependent. It is true that one can not acquire a high degree of knowledge without having some intelligence and the highly intelligent person certainly acquires knowledge because it is of great use, but, a person may have knowledge that is out of proportion to his intelligence and vice versa.

The last statement especially forces us to make at least an attempt to define our terms. What do we mean by intelligence and what do we mean by knowledge? We have said that the one is inborn, the other acquired. Intelligence is the potentiality of the machine. Knowledge is the material upon which it works. Knowledge is the raw material. Intelligence determines what we do with it. The effectiveness of a machine ( what it can do), depends upon its structure and its functioning. Likewise, intelligence is dependent upon the structure of the brain cells which condition given mental processes, and second, upon the functioning of those cells.

A hand printing press is a machine of very simple structure and has a simple function of spreading ink upon paper according to a prearranged plan. Its structure may be of the simplest, merely a square block of metal, wood or rubber cut into the desired form upon which the ink is spread and then the block placed against the paper. Twenty-six such blocks used individually in the prescribed order is sufficient to put upon the paper any message in the English language and by repetitions of the process one can make as many copies as one likes. This would be an example of very simple structure and a very simple functioning. We may elaborate the structure of this machine so that it will hold together the different blocks in the prescribed order so that they can all be impressed at once upon the paper. We have thus elaborated the structure slightly and extended its function and thus attained to a higher level of printing.

A higher level is reached when we elaborate the structure by the addition of guides, wheels and levers so put together and arranged that it is only necessary to place the paper of the right size in a particular position and the copies are produced as rapidly as the paper can be placed.

A still higher level of structure and functioning is attained when the machine is so elaborated that it is only necessary to place a pile or a roll of paper in a given position and the machine picks up a piece of paper, places it under the type, prints it, puts it out of the way and repeats the process. And so by adding new structure to our machine in such a way that new f imctions are possible, we may finally arrive at a machine that needs only to have a supply of the raw material in the shape, for instance, of sheets of paper cut in a definite shape, when it will pick up the paper a sheet at a time, print it, spread glue on certain prescribed edges of the sheet, fold over and press together some of those edges until we have an envelope which continuing through the machine, the gum on the flap is dried and then the flap is folded over and the completed envelopes are counted, pushed out, grouped in packages of twenty-five, a band placed around the bundle and dropped into a box. The structure of such a machine is exceedingly complicated and the functioning is so surprising that it is a common remark that the machine is "almost intelligent. " We, thus, have a very high level of mechanical efficiency. This is comparable to intelligence. This machine may exercise its complete function upon paper and a printers ink made from lamp black and oil. These are the raw materials comparable to knowledge. But the same machine is capable of using other raw materials. It may use innumerable kinds of ink made from widely different substances. It may print upon paper of many different kinds, upon cloth, wood, metal and numerous other substances. It may make envelopes of different sizes and shapes with no change of its structure and only a slight change

LEVELS OP INTELLIGENCE 11

of functioning. It may count them out in tens or fifties or any other numbers and thus its usefulness is enormously increased, but it will be noticed it is the same machine, the same structure and functions. We have merely increased the range of its raw materials. Knowledge is to intelligence what the raw material is to the machine. This is, to be sure, a crude and inadequate illustration of the human machine and yet the analogy is sufficiently close and accurate to help us to comprehend the relation of intelligence to knowledge, which is fundamental to an appreciation of the doctrine of mental levels.

It may be said that one may have considerable knowledge with little intelligence. The simple hand press, our lowest level of mechanical structure in the printing press, might nevertheless be supplied with quantities of all kinds of ink and material to be printed ; but it could never use all of that material because the process is too slow and because the structure would not permit of its being used upon all kind of substances. It could never make an envelope because its structure is wholly inadequate. Low grade intelligence cannot use much knowledge. In our illustration it is always possible to distinguish the machine or any part of it from the raw material upon which it works. In considering the work of the human being this is not the case, hence, the confusion to which we have referred, between intelligence and knowledge.

Many a person is estimated as of high intelligence who in reality has only a somewhat unusual supply of knowledge. The extreme of this is familiar in the man who, as it is commonly expressed, "is a walking encyclopedia" but who makes almost no use of his knowledge for the usually unappreciated reason that he has not the natural intelligence necessary. A man well known to the writer has an intimate knowledge of the facts of history sufficient to have made him a statesman; but lacking the intelligence to use his valuable acquisition in this line he spent a perfectly colorless life unknown outside of his own township and unappreciated even there.

The second important reason why the theory of mental levels is hard to accept is to be found in the fact that while we know that children generally increase in intelligence from birth to maturity we have never appreciated the exceptions. Let us consider the accompanying diagram.

The vertical lines with their increasing height may represent the increase of intelligence as the years increase. This we have observed and ac-

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.2 aS <U fe S o v fe cepted. The horizontal lines will represent what we have not appreciated, viz., that some of the people who attain to the mental level of six, for instance, stop there and as the years go by will always be found on that level. We have, it is true, begun to appreciate the fact of arrested mental development. What we have not begun to appreciate is the proportion of human beings who have stopped at the ages of ten, twelve, fourteen years. If we seek for the reason for this oversight it is to be found partly in the confusion of intelligence with knowledge and partly also, in the fact that we confuse mental development with physical development. Because the boy of ten whose mental development may have ceased at that point, continues to develop physically our estimate of him follows the physical development which is so obvious ; and we fail to appreciate the mental side which is obscure. It is a notorious fact that men judges and men physicians refuse to admit a girl is feeble-minded if she is pretty.

As long as we had no scientific method of determining the mental level it was but natural that we should fail to appreciate it. What then are the methods of interpreting the mental level and what are the results of using those methods? I shall not weary you with the details of the tests used or the systems of tests, but, rather attempt to emphasize some of the principles of mental testing that have been too little appreciated and are still too often ignored. The assumptions underlying the determination of mental level are :

First, there is an orderly development of intelligence from birth to an upper limit as yet not accurately determined.

Second, it is possible to observe and measure this development independent of the acquired knowledge. Moreover a test of a child's knowledge has only an indirect value as when a person who has not succeeded in acquiring knowledge, we may explain his failure on the basis of lack of intelligence. But that is an indirect argument which is only resorted to in borderline cases or for purposes of confirmation.

The first assumption does not need discussion so far as its main theme is concerned. It has been objected that while there is an orderly development that order is peculiar to each individual and that the individual variations are so great that it is impossible to have one standard. It has been maintained rather strongly that children do not develop equally on all sides, but on the contrary very unevenly ; that one child is strong where another is weak. There is no denying that the facts upon which this statement is made are true. What has not been appreciated is the fact that they have no bearing upon the problem of measuring the intelligence level. The differences and peculiarities that are a matter of common observation are the manifestations of intelligence and not the intelligence itself. To go back to our analogy of the printing press, one printer may use black ink, another red or green. One may make a specialty of printing on silk, another on parchment, one may show one kind of product and another another, but it is always the same machine.

Our second assumption needs more careful consideration. It is rather popular to deny in toto that intelligence can be measured. This view has persisted apparently for two main reasons; first, the confusion with knowledge with the added consideration that knowledge is more in evidence ; and second, from a misconception of the nature of mind. This misconception is natural enough, because the psychologist has been in the habit of discussing the various phases and manifestations of mind as though they were separate entities, a process justifiable for purposes of study but exceedingly misleading when it comes to the application to practical problems. Even if the psychologist's description of attention, memory, perception, reasoning, will, etc., is correct, and even if we could measure the strength of these in a particular child, it would be utterly unsafe and irrational to conclude that we could predict what the result would be when some or all of these processes are combined into that function which we call intelligence.

Even in the material world it is often unsafe to attempt to predict what will be the properties of a synthetic product. For example, the properties of steel are well known, also the properties of vanadium, but no one would have dared predict that the addition of seventeen hundredths of one percent of vanadium to a quantity of steel would produce a product that differs from both to the extent that vanadium steel differs from either one.

In the matter of tests of intelligence this error has been made repeatedly. At one time there was a strong demand for a statement of what each question tested; in the Binet Measuring Scale of Intelligence for instance, it was asked which were tests of attention, which of memory or perception or reasoning. It was very difficult to convince students that this was an irrational procedure ; especially difficult since it is true that different types of questions do call for a grade of intelligence in which now memory predominates, now reasoning and now something else. But it is important to remember at all times that we are testing intelligence. To revert to our figure of the printing press it is as though one took it to pieces and laid out the different parts and then concluded that he could judge of the efficiency of the machine by the perfection of those parts. It' is obvious that the real question is, — how do they work together?

No machinist, however skilled could, by looking at the parts thus spread out, predict whether the machine would work or not — still less tell what it would do. If this is true, even of the most complicated machine, how much more true of anything so complicated as the human mind.

If it is granted then that intelligence develops and that it can be measured, our next question is, — how is it to be done? The answer is easy, its application difficult. It is only necessary to devise a series of tasks that involve the application of the varying degrees of intelligence; arrange these tasks in order of difficulty and then by setting the tasks to a child ascertain how far along the scale he has gone. Binet arranged his tasks or test questions according to age. This is simple and practicable and although other types of scales have been suggested it seems probable that nothing can take the place of an age grade rating. This means that we ascertain what tasks or test questions the children of the various chronological ages can do. We find, for instance, that children of five years can answer certain questions which children of four years cannot answer, and the five year olds in turn, cannot answer the questions that belong to six year intelligence. Thus we have standards for each age, and we can compare any person old or young with these standards. Many have thought that because the original purpose of the tests was to discover defectives, they were not valid for normal children. Such persons have failed to understand the real nature of the tests.

Others have thought that while they are useful for children they are not valid for adults. They are surely reliable for feeble-minded adults and as for normal adults the original Binet tests had norms only up to twelve years. The Stanford Revision however, has extended this to "superior adult."

It must be borne in mind that the task set must be such as calls for native intelligence and not knowledge. Skepticism in regard to the validity of tests is the result largely of a confusion of intelligence with knowledge. One constantly hears the objection that such a child has not had an opportunity to learn certain things. If the question is one that depends upon the acquisition of knowledge then it is not a suitable test of intelligence. While it is probable that no measuring scale so far devised entirely gets away from more or less influence of knowledge and education, yet the questions are so arranged that on the whole it has very little influence. The truth of this is proved by the results.

Let us now consider the results obtained in the use of mental tests, for after all the truth of the theory must be determined by the validity of the results. I shall not bother you with statistics or detailed statements of results in special cases. Suffice it to say that the results have surpassed all expectations. The mental level of a person as determined by any standardized measuring scale of intelligence is found to agree remarkably with his mentality as it is judged by his adaptation to his environment; and in practically all cases where the mental level of abnormal persons is determined it is accepted as the adequate explanation of conduct previously unintelligible. Not only that but the method has proved to be so elastic that it is but little affected by what we may call rough usage.

It was long contended, for example, that the scale would be of no value except in the hands of those who had received long and extensive training. It was thought that the so-called personal equation of the examiner would often invalidate the test. It was thought that the person examined must be kept under most rigid laboratory conditions. It was thought that children would communicate to each other the results and thus render the procedure invalid. These and many other difficulties were anticipated. As a matter of experience practically none of these has proved serious.

It is true that statistical studies of large groups have shown variations in personal equation, in the effect of different procedures, and so on. But so far as any one individual child is concerned his mental level is determined with an error so slight as to be negligible. These statements must not be confused with the question of diagnosis which is an entirely different matter. We may for example determine that a twelve year old child has a ten year mental level. Whether such child is to be considered a case of mental arrest, feeble-minded, is an entirely different question which depends upon many other factors. Here as elsewhere, diagnosis is difficult and requires a great deal of training and experience in all borderline cases. If a twelve year old child tested four there would be no difficulty in either case, that is, of determining the mental level or of deciding upon feeble-mindedness.

If in the past there has been any doubt of the truth of these statements, there can be no question now with the experience of the army tests in mind. Over one million, seven hundred thousand men in the army have been tested by these methods, their mental level determined and recorded. The results were so uniformly accurate and in agreement with the experience of the officers, that they were quickly accepted and used as a basis for procedure. Officers were appointed from the men who were found by the tests to be most intelligent. Those who were found to be least intelligent, proved also to be dull as determined by the daily routine and were recognized as of too low mentality to be profitable to send overseas. These results have been published and we shall not reproduce them. We may, however, as a basis for our later discussion draw some very significant inferences from the results so far published.

The significance of these results will be appreciated when we consider that one million and seven hundred thousand drafted men in the army may be accepted as a fair sample of the population of the United States. Whatever we may determine in regard to that group of men we shall probably find applicable to the country as a whole. It is thus probable that we can find in these results, suggestions and conclusions of profound importance as bearing upon our social problems and social well being. It will be recalled that the Army Tests were, for the most part, group tests ; that is, the men were examined in groups of fifty to three hundred. Moreover, the scale used was essentially a Point Scale, that is to say in what is known as the Alpha test were two hundred and twelve points, possibly obtainable. The accompanying chart is made from the figures given out by the Surgeon General. We quote from the official report : "Explanation of Letter Ratings. The rating a man earns furnishes a fairly reliable index of his ability to learn, to think quickly and accurately, to analyze a situation, to maintain a state of mental alertness, and to comprehend and follow instructions. The score is little influenced by schooling. Some of the highest records have been