# Popular Science Monthly/Volume 83/August 1913/Eugenics: With Special Reference to Intellect and Character

 EUGENICS: WITH SPECIAL REFERENCE TO INTELLECT AND CHARACTER[1]
By Professor EDWARD L. THORNDIKE

TEACHERS COLLEGE, COLUMBIA UNIVERSITY

BY eugenics is meant, as you all know, the improvement of mankind by breeding. It has been decided by those responsible for this lecture—Mrs. Huntington Wilson and the president and trustees of the university—that its topic shall be the intellectual and moral, rather than the physical, improvement of the human stock.

Common observation teaches that individuals of the same sex and age differ widely in intellect, character and achievement. The more systematic and exact observations made by scientific students of human nature emphasize the extent of these differences. Whether we take some trivial function—such as memory for isolated words, or delicacy of discrimination of pitch—or take some broad symptom of man's nature, such as his rate of progress through school, or ability in tests of abstract intellect, or even his general intellectual and moral repute—men differ widely. Samples of the amount and distribution of such differences are given in Charts 1, 2 and 3. Chart 1 relates that of 732 children who had studied arithmetic equally long, one could get over a hundred examples done correctly in fifteen minutes, while others could not get correct answers to five. Even if we leave out of account the top three per cent., covering all the records of 60 or over, we have some children achieving twenty-five times as many correct answers as other children.

Chart 2 shows that when four hundred children who had had similar school training were given each the same amount of practise in certain work in division, some improve not at all, and others enormously. Chart 3 shows that of children in the same school all of the same year-age (thirteen), some have done the work of the eight grades of the elementary school and of one or two years of the high school, while others have not completed the work of a single year. Still less competence at intellectual tasks could be found by including children from asylums for imbeciles and idiots.

The differences thus found amongst individuals of the same sex and age are due in large measure to original, inborn characteristics of the intellectual and moral constitution of the individuals in question. They are, it is true, in part due to differences in maturity—one thirteen-year old being further advanced in development than another. They are also due in part to differences in environment, circumstances, training—one sort of home-life being more favorable than another to progress through school, for example. Each advance in the study of individual

Chart 1. The Relative Frequencies of Different Degrees of Ability in Addition in the Case of Fourth-grade Pupils.

differences, however, shows that differences in maturity and differences in the circumstances of nurture account for only a small fraction of the differences actually found in individuals of the same general environment of an American city in 1900-1912. Long before a child begins

Chart 2. The Relative Frequencies of Different Amounts of Gain from Fifty Minutes of Practise in Division, in the Case of Pupils of the Same School Grade.

his schooling, or a man his work at trade or profession, or a woman her management of a home—long indeed before they are born—their superiority or inferiority to others of the same environmental advantages is determined by the constitution of the germs and ova whence they spring, and which, at the start of their individual lives, they are.

Of the score or more of important studies of the causes of individual differences which have been made since Francis Galton led the way, I do not find one that lends any support to the doctrine of human initial

Chart 3. The Relative Frequencies of Different Amounts of Progress in School of Thirteen-year-old Children.

equality, total or approximate. On the contrary, every one of them gives evidence that if the thousand babies born this week in New York City were given equal opportunity they would still differ in much the same way and to much the same extent as they will in fact differ.

We find, for instance, that the children of certain families rank very much higher in certain psychological tests of perception, association and the like, than the children of certain other families. Now if this difference were due to the difference between the two groups of families in environment—in ideals, customs, hygienic conditions and the like—it should increase greatly with the age of the children in some rough proportion to the length of time that they are subject to the beneficent or unfavorable environment. It does not. One family's product differs from another nearly as much at the age of 9 to 11 as at the age of 12 to 14.

Again, if inequalities in the environment produce the greater part of these differences, equalizing opportunity and training should greatly reduce them. Such equalization is found by experiment to reduce them very little, if at all. Chart 4 shows, for example, the result of equal amounts of training applied to two groups of adults whom life in general had previously brought to the conditions shown at the left of the chart. The trait chosen was addition; from life in general one group had gained the ability to do twenty-seven more additions per minute than the other group, accuracy being equal in the two groups. At the end of the special training the superior individuals had gained on the average 28 additions per minute, while the inferior individuals gained only 10 additions per minute. As a result of this partial equalization of opportunity, the superior individuals were farther ahead than ever! If equality of opportunity has no equalizing effect in so easily alterable a trait as rapidity in addition, surely it can have little power in such

Chart 4. The Relation of the Gains from Equal Amounts of Practise in the Case of Individuals of High and Low Initial Ability.

traits as energy, stability, general intellectual power, courage or kindliness.

Men differ by original nature. With equal nurture of an inferior sort they progress unequally to low stations; with equal nurture of a superior sort they progress unequally to high stations. Their absolute achievements, the amounts of progress which they make from zero up, are due largely to the environment which excites and directs their original capacities. Their relative achievements—the amounts of progress which they make, one in comparison with another—are due largely to their variations one from another in original capacities.

The man's original nature, too, has large selective power over his environment. The thousand babies will in large measure each create his own environment by cherishing this feature and neglecting that, amongst those which the circumstances of life offer. As Dr. Woods has well argued, the power of the environment to raise or lower a man is very great only when the environment is unavoidable. We must remember that one of these babies, if of mean and brutal nature, can by enough pains avoid industry, justice and honor, no matter how carefully he is brought up; and that one of them of intellectual gifts can, if he cares enough, seek out and possess adequate stimuli to achievement in art, science, or letters, no matter how poor and sordid his home may be.

If, a hundred years ago, every boy in England could have had as good opportunity—each of the sort fitted to his capacities—as Charles Darwin had, the gain for human welfare would probably have been great; but if every boy then could have had as good inborn capacity for science, art, invention, the management of men—or whatever his strongest capacity was—as Charles Darwin had for science, the gain for welfare would certainly have been enormous.

The original differences in intellect, character, and skill which characterize men are related to the families and races whence the individuals spring. Each man's original mental constitution, which so largely determines how much more or less he will do for the world's good than the average man of his generation, is the product of no fortuity, but of the germs of his parents and the forces which modify the body into which they grow—is the product, as we are accustomed to say, of heredity and variation. The variation within the group of offspring of the same parents is large—a very gifted thinker may have an almost feeble-minded brother—but the variation between families is real. A feeble-minded person's brothers will be feeble-minded hundreds of times as often.

The general average tendency of the original intellectual and moral natures of children to be like the original natures of their ancestry is guaranteed beforehand by the accepted principles of biology. Direct evidence of it is also furnished by investigations of the combination of original and acquired differences which human achievements, as they stand, display. The same studies which find differences of nurture hopelessly inadequate to account for differences of ability and achievement, find that original capacities and interests must be invoked precisely because achievement runs in families, and in a manner or degree which likeness in home training can not explain. Galton found that the real sons of eminent men had a thousand times the ordinary man's chance of eminence and far excelled the adopted sons of men of equal eminence. "Woods has shown that, when each individual is rated for intellect or morals, the achievements of those sons of royal families who succeeded to the throne by paternal death and thus had the special attention given to crown princes and the special unearned opportunities of succession, have, in the estimation of historians, been no greater than those of their younger brothers.

Children of the same parents resemble one another in every mental trait where the issue has been tested, and resemble one another nearly or quite as much in such tests as quickness in marking the A's on a sheet of printed capitals or giving the opposites of words, to which home training has never paid any special attention, as they do in adding or multiplying, where parental ambitions, advice and rewards would be expected to have much more effect, if they have any anywhere.

Mr. Courtis, who has been assiduously studying the details of ability in arithmetic in school children, finds, as one sure principle of explanation, the likeness of children to parents—and this even in subtle traits and relations between traits, of whose very existence the parents were not aware, and which the parents would not have known how to nurture had they known of their existence.

Dr. Keyes has recently made an elaborate study of various possible causes of the rate of progress of a child through the elementary school. He traces the effects of defective vision, of sickness, of moving from one school to another, and so on, but finds nothing of great moment until he happens to trace family relationships. Then it appears that certain families are thick with "accelerates," or pupils who win double promotions, whereas other families are thick with retarded pupils, who require two years to complete a normal year's work. Of 168 families, only 30 contain both an "accelerated" and a "retarded" pupil, whereas 138 show either two or more accelerates or two or more retarded pupils. The differences in home training are here not allowed for, but, in view of what has been found in other cases, it appears certain that the rate at which a child will progress in school in comparison with his fellows is determined in large measure before he is born.

In intellect and morals, as in bodily structure and features, men differ, differ by original nature, and differ by families. There are hereditary bonds by which one kind of intellect or character rather than another is produced. Selective breeding can alter a man's capacity to learn, to keep sane, to cherish justice or to be happy.

Chart 5. The Improvement Possible by Selective Breeding. The upper surface being taken to represent the existing distribution of Intellect, the lower surface represents what might be expected from, say, ten or twenty generations of breeding exclusively from the apparently best tenth of human Intellects.

Let the lines ${\displaystyle L_{1}H_{1}}$ and ${\displaystyle L_{2}H_{2}}$ in Chart 5 be identical scales for the original capacity for intellect, or virtue, or any desirable human trait. Let the surface above line ${\displaystyle L_{1}H_{1}}$ represent the distribution of this original capacity amongst men to-day. There is every reason to believe that wise selective breeding could change the present state of affairs, at least to that shown above ${\displaystyle L_{2}H_{2}}$, within relatively few generations. Perhaps it could do even more. There is every reason also to believe that each step of improvement in the original nature of man would, in and of itself, improve the environmental conditions in which he lives and learns.

So much for the general possibility of eugenics in the case of intellect, morals and skill—for what should soon be in every primer of psychology, sociology and education, and be accepted as a basis of practise by every wise family, church and state.

The next question concerns the extrinsic effects of selective breeding for intellect or for morals, the possibility of injuring the race indirectly by a change in, say, intellect which in and of itself is desirable. If we breed horses for speed, they are likely to lose in strength and vigor; do we run such risks in breeding men for intellect, or for morals, or for skill? This question has been neglected by the hortatory type of enthusiasts for eugenics. It has also not received the attention which it deserves from the real workers for racial improvement, probably because the psychological investigations which answer it are little known. They do, however, give a clear and important answer—that there is practically no chance whatever of injury from selective breeding within a race for intellect, or for morality, or for mental health and balance, or for energy, or for constructive ingenuity and skill—no risk that the improvement of any one of these will cause injury to any other of them, or to physical health or happiness. The investigations have found that, within one racial group, the correlations between the divergences of an individual from the average in different desirable traits are positive, that the man who is above the average of his race in intellect is above rather than below it in decency, sanity, even in bodily health. Chart 6 shows, for example, the average intellect of each of the groups, when individuals are graded 1, 2, 3, 4, etc., up to 10 on a scale for morality, according to Woods's measurements of royal families. I may add that the effect of chance inaccuracies in Woods's ratings, whereby one individual is rated as 8 or 10 when he should have been rated 9, or is rated 4 or 8 when he should have been rated 6, is to make this obtained and shown relation of intellect to morals less close than it really is.

Nature does not balance feeble-mindedness by great manual dexterity, nor semi-insane eccentricities by great courage and kindliness. Correlation of divergences up or down from mediocrity is the rule, not compensation. The child of good reasoning powers has better, not worse, memory than the average; the child superior in observation is superior in inference; scholarship is prophetic of success out of school; a good mind means a better than average character. The fifty greatest warriors of the world will be above the average man as poets. The fifty greatest artists of the world will be better scientists than the average. Genius of a certain type does, via the nervous temperament, ally itself to eccentricities of a certain type; and very stupid men can not be rated as insane because they are already idiots; but on the average the most

Chart 6. The Relation between Intellect and Morality in European Royal Families. After Woods.

intellectual tenth of the population would, under equal conditions of strain, furnish fewer lapses into insanity than its proportional quotum.

Selective breeding for superior intellect and character does not then require great skill to avoid injurious by-products or correlatives of intrinsically good traits. Intrinsically good traits have also good correlatives. Any method of selective breeding, then, which increases the productivity of intellectually or morally good stock over that of poor stock, will improve man, with one possible added requirement—that breeding should be for fertility as well, should not be suicidal, should not make the race better, but at the same time put an end to it altogether!

It might be that there was a necessary inverse correlation in human nature between fecundity and high intellectual and moral station whereby, the better men became, the fewer offspring they would have; and whereby, at a certain limit of super-manhood, reproduction would cease. Certain changes of the birth-rate with time, and certain variations in it amongst groups, have given some students the impression that intellect, at least, is, by natural necessity, inversely correlated with fecundity.

It is hard to find the facts by which to either verify or refute the notion, current in superficial discussions of human nature and institutions, that such is the case. Sad testimony to man's neglect of the question which of all questions perhaps concerns him most—the simple question of which men and women produce the men and women of the future—is given by the fact that almost no clear and reliable evidence is available concerning the relations of fecundity to intellect, morality, energy, or balance. The most significant evidence is that collected by Woods in the case of royal families. Woods gives the number of children living till 21 in the case of each individual of the royal families which he studied. From them I have made the summaries noted on Charts 7 and 8. Each of these sets of facts is of course the

The Relation of Morality of Mother to Number of Children.

result of the constitutional fecundity of the women in question plus certain very intricate cooperating circumstances; and neither can be taken at its face-value. What the birth rate would have been had the constitutional capacity of each woman worked under equal conditions, can only be dubiously inferred. My own inference from relevant facts concerning the studies of differentiated birth rates with which I am acquainted is that morality, mental health, energy, and intellect perpetuate a family, and that wherever the really better, or saner, or stronger, or more gifted, classes fail to equal the really worse, ill balanced, feeble or stupid classes, it is a consequence of unfortunate circumstances and customs which are avoidable and which it is the business of human policy to avoid. Society may choose to breed from the bottom, but it does not have to.

No great ingenuity or care then seems necessary to make fairly rapid improvement in the human stock. The task is only the usual one of any rational idealism—to teach people to want a certain thing that they ought to want, and to change social usages so as to satisfy this new want. The same sort of tuition whereby men are learning to want those

Chart 8. The Relation of Intellect of Mother to Number of Children.

who are alive with them to be healthier, nobler and more capable, will serve to teach us to want those who are to live with our children's children to be healthier, nobler and more capable. Provided certain, care is taken to favor the sane, balanced type of intellect rather than the neurotic, any selective breeding which increases the fecundity of superior compared to inferior men, and which does not produce deterioration in the physical and social conditions in which men live, will serve.

The danger of deterioration in physical and social conditions from breeding for intellect and morals is trivial. The effect is almost certain to be the opposite—an improvement in physical and social conditions. The more rational the race becomes, the better roads, ships, tools, machines, foods, medicines and the like it will produce to aid itself, though it will need them less. The more sagacious and just and humane the original nature that is bred into man, the better schools, laws, churches, traditions and customs it will fortify itself by. There is no so certain and economical a way to improve man's environment as to improve his nature.

Each generation has of course to use what men it has to make the world better for them; but a better world for any future generation is best guaranteed by making better men. Certain worthy customs of present civilization may be endangered by rational control of who is ta be born, though this seems to me unlikely. In any case, we may be sure that if the better men are born they will establish better customs in place of those whose violation made their birth possible.

It is not by a timid conservatism sticking to every jot and tittle of the customs which gifted men of the past have taught the world, that we shall prevent backsliding: it is far safer to trust gifted men of the present and future to keep what is good in our traditions, and to improve them. The only safe way to conserve the good wrought by the past is to improve on it.

It is beyond the province of this lecture to devise biologically helpful and socially innocuous schemes of selective breeding, but I may be permitted to record my faith that if mankind to-day really wanted to improve the original nature of its grandchildren as much, say, as it wants to improve the conditions of life for itself and its children, and believed certain facts of biology and psychology as effectively, say, as it believes that wealth gives power or that disease brings misery, appropriate schemes for selective breeding would be devised well within the span of our own lives.

Any form of socially innocuous selective breeding will improve the stock by reproducing from those members of it who have shown, by ancestral and personal achievement, with due allowance for favorable or unfavorable circumstances, the superiority of the germ plasm which they bear. But some forms may be far more effective than others according to the way in which the original components of intellect, character, energy, skill, stability and the like in the germs are constituted. Suppose, for example, that the original germinal basis for human intellect consisted in the presence of a certain constant something, call it ${\displaystyle I_{n}}$, the determiner for intellect," in the germ or ovum. The fertilized ovum, which is the human life at its beginning, could then have ${\displaystyle I_{n}}$ double, if both the germ and ovum had it; ${\displaystyle I_{n}}$ single if one or the other had it; or could lack ${\displaystyle I_{n}}$ as it must if neither had it. Suppose that the consequences of these three conditions were that the ${\displaystyle I_{n}I_{n}}$ individuals would tend, with fair conditions in life, to be specially gifted; that the In individuals would tend to be of "normal" intellect; that the individuals lacking ${\displaystyle I_{n}}$ would tend to be feeble-minded. It is then the case that of the germs produced by the individual who had ${\displaystyle I_{n}I_{n}}$ at the start of his life, each contains ${\displaystyle I_{n}}$, that of the germs produced by the individual who had ${\displaystyle I_{n}}$ at the start of his life, half have ${\displaystyle I_{n}}$ and half lack it, and that of the germs produced by the individual who lacked ${\displaystyle I_{n}}$ at the start of his life, no one has ${\displaystyle I_{n}}$. Consequently, by discovering the individuals who lacked ${\displaystyle I_{n}}$ at the start of life and preventing them from breeding, we could rapidly reduce feeble-mindedness. By discovering the individuals who had ${\displaystyle I_{n}I_{n}}$ at the start of life and breeding exclusively from them, we could eradicate feeble-mindedness and ordinariness both, leaving a race of only the specially gifted. The discovery could be made in a few generations of experimental breeding; and the exclusion, of course, could be made one generation after the discovery.

This supposition will be recognized by many of you as a simplified case of Mendelian inheritance of a unit character due to the presence or absence of a single determiner which can either be or not be in a germ or ovum, and which "segregates."

No case quite so simple as this can be true of human intellect, but something approximating it has been suggested as perhaps true.

Suppose, on the other hand, that the germinal basis for intellect consists in the presence, in the germ or ovum, of one or more of four determiners—${\displaystyle I_{1},I_{2},I_{3}}$, and ${\displaystyle I_{4}}$—contributing amounts 1, 2, 3 and 4 of intellectual capacity. The fertilized ovum could then have any one of 256 different constitutions ranging from the entire absence of all these determiners to the presence of each one "duplex"—i. e., in both germ and ovum. If such duplex presence meant that the two contributions combined additively, the original intellect of the individual could range from to 20. Individuals, all of one same original intellect—10—might be of very different germinal constitutions, and so of very different possibilities in breeding. If two individuals, each of original intellect 10, were mated, it might be the case that their possible offspring would range in intellect from to 20, or it might be that they could not go below 8 or above 12.

If the number of germinal determiners of intellect is increased to five or six, the task of telling the constitution of the germs produced by any individual of known original intellectual capacity is enormously increased; and the research needed to guide the best possible breeding of man is very, very much more laborious. Moreover, instead of hoping to bring man to the best possible status (subject to the appearance of new desirable mutations) by a few brilliant rules for marriage, we must then select indirectly and gradually by parental achievement rather than directly by known germinal constitution, just as animal and plant breeders had to do in all cases until recently, and just as they still have to do in many cases. Only after an elaborate system of information concerning family histories for many generations is at hand, can we prophesy surely and control with perfect economy the breeding for a characteristic which depends on the joint contributions of five or six determiners. For it is just as hard to "breed in" a determiner that raises intellect or morality only one per cent, as it is to "breed in" one which raises it a hundred per cent.—provided, of course, the latter determiner exists. And it is thousands of times harder to discover the distribution of a determiner in the human race's germs when it is one of ten that determine the amount of a trait, than when it is one of two.

The germinal determination of intellect, morality, sanity, energy or skill is, so far as I can judge, much more like the second complex state of affairs than the first simple one. Important observations of the inheritance of feeble-mindedness and insanity have been made by Davenport, Goddard and Rosanoff, which they interpret as evidence that original imbecility is due to the absence of a single determiner, and that an originally neurotic, unstable mental organization is explainable almost as simply. It is with regret that I must assure you that these observations are susceptible of a very different interpretation. Much as I should like to believe that these burdens on man's nature are each carried in heredity in a single package, which selective breeding can shuffie off in a generation or so, I can not. A eugenics that assumes that intellect, morality, sanity and energy are so many single niches in the germs which selective breeding can, by simple transfers, permanently fill, is, I fear, doomed to disappointment and reaction. I dare to believe that the time will come when a human being idiotic by germinal defect will be extinct like the dinosaur—a subject for curious fiction and for the paleontology of human nature; but I have no hope that such a change can be made with the ease with which we can change short peas to tall, curly-haired guinea pigs to sleek, or plain blossoms to mottled ones.

There is another fundamental question whose answer is needed for the most economical selective breeding of human nature, a question which time permits me only to mention, not to describe clearly. Stated as a series of questions, it is this: Do the germs which a man produces—his potential halves of offspring—represent a collection peculiar to him, or only a collection peculiar to some line, or strain, or stock, or variety, of mankind of which he is one exemplar?

Suppose a hundred men and a hundred women to exist, each with identical germinal constitutions, so that, say, in every case one tenth of the germs (or ova) would be of quality 5; one fifth, of quality 6; two fifths, of quality 7; one fifth, of quality 8; and one tenth, of quality 9. Suppose that they mated and had five hundred offspring. Suppose that the best fifty of this second generation married exclusively among themselves; and similarly for the worst fifty. Would the offspring of these two groups differ, the children of the best fifty being superior to the children of the worst fifty? Or would this third generation revert absolutely to the condition of the grandparental stock whence they all came; and be alike, regardless of the great difference in their parentage?

Does the selection of a superior man pay because his superiority is, in and of itself, a symptom of probable excellence in his germs; or only because his superiority is a symptom that he is probably of a superior "line" or strain?

That the second answer of each pair may be the true one, is a natural, though not, I think, an inevitable, inference from the work of Johanssen, Jennings and others. They have found selective breeding within any one pure line futile, save when some peculiar and rare variations have taken place within it. Their work is of very great importance and forms the best introduction to the general problem of the limits to human racial improvement. I regret that time is lacking to describe these studies of heredity within one "pure line." It is from such that eugenics may hope to learn valuable lessons in economy of effort and exactness of expectation. I have, however, already taken too much of your time with the problems of the exact laws whereby good men have good offspring and whereby breeding for strength, wisdom and virtue may be most effective.

In the few minutes that remain let me sum up what might perhaps have been entitled the A B C of eugenics in the realm of mind.

I have tried to show that, in intellect and character, men differ, by original nature, in some sort of correspondence to the ancestry whence they spring, so that by selection of ancestry the intellect and character of the species may be improved; to show also that injurious by-products of such selective breeding are very easily avoided, if indeed they occur at all; and, finally, to state some of the problems whose answers will inform us of just how the original intellect and character of one man does correspond with that of his ancestors, and so of just the best ways to discover the best strains and to perpetuate them.

I hope to have made it clear that we have much to learn about eugenics, and also that we already know enough to justify us in providing for the original intellect and character of man in the future with a higher, purer source than the muddy streams of the past. If it is our duty to improve the face of the world and human customs and traditions, so that men unborn may live in better conditions, it is doubly our duty to improve the original natures of these men themselves. For there is no surer means of improving the conditions of life.

It is no part of my office to moralize on these facts. But surely it would be a pitiable thing if man should forever make inferior men as a by-product of passion, and deny good men life in mistaken devotion to palliative and remedial philanthropy. Ethics and religion must teach man to want the welfare of the future as well as the relief of the cripple before his eyes; and science must teach man to control his own future nature as well as the animals, plants, and physical forces amongst which he will have to live. It is a noble thing that human reason, bred of a myriad unreasoned happenings, and driven forth into life by whips made aeons ago with no thought of man's higher wants, can yet turn back to understand man's birth, survey his journey, chart and steer his future course, and free him from barriers without and defects within. Until the last removable impediment in man's own nature dies childless, human reason will not rest.

1. A lecture given at Columbia University, in March, 1913.