INDIVIDUAL DIFFERENCES

The meaning of individual differences. The major part of this volume has been devoted to a consideration of those traits, interests, and capacities which all individuals share, and which may in general be described as the "original nature of man." These distinctive inborn tendencies were treated, for purposes of analysis, in the most general terms, and, on the whole, as if they appeared in the same strength and variety in all individuals. When we thus stand off and abstract those characteristics which appear universally in all individuals, human nature appears constant. But there are marked variations in the specific content of human nature with which each individual is at birth endowed. Put in another way, one might say that to be a human being means to be by nature pugnacious, curious, subject to fatigue, responsive to praise and blame, etc., and susceptible to training in all these respects. By virtue of the fact that we are all members of the human race, we have common characteristics; by virtue that we are individuals, we all display specific variations in specific human capacities. There is, save abstractly, no such thing as a standard human being. We may intellectually set up a norm or standard, but it will be a norm or standard from which every individual is bound to vary.

The fact that individuals do differ, and in specific and definable respects, has most serious consequences for social life. It means, briefly, that while general inferences may be drawn from wide and accurate observations of the workings of human nature, these inferences remain general and tentative, and if taken as rigid rules are sure to be misleading. Theories of education and social reform certainly gain from the general laws that can be formulated about original human traits, fatigue, memory, learning capacity, and the like. But they must, if they are to be applicable, take account also, in a precise and systematic way, of the variety of men's interests and capacities. To this fact of variety in the original nature of different men social institutions and educational methods must be adapted. Arbitrary rules that apply to human nature in general do not apply to the specific cases and specific types of talent and desires. Educational and social organizations can mould these, but the result of these environmental influences will vary with individual differences in original capacities. We can waste an enormous amount of time and energy trying to train a person without mechanical or mathematical gifts to be an engineer. We not only save energy and time, but promote happiness, if we can train individuals so that their specific gifts will be capitalized at one hundred per cent. They will be at once more useful to society and more content with themselves, when they are using to the full their own capacities. They will at once be unproductive and unhappy when they find themselves in activities or social situations where their genuine talents are given no opportunity and where their defects put them at a conspicuous handicap.

Individuals differ, it must further be noted, not only in specific traits, but in that complex of traits which is commonly called "intelligence." In the broadest terms, we mean by an individual's intelligence his competence and facility in dealing with his environment, physical, social, and intellectual. This competence and facility, in so far as it is a native endowment, consists of a number of traits present in a more or less high degree, traits, for example, such as curiosity, flexibility of native and acquired reactions, sociability, sympathy, and the like. In a sense an individual possesses not a single intelligence, but many, as many as there are types of activity in which he engages. But one may classify intelligence under three heads, as does Thorndike:[1] mechanical intelligence, involved in dealing with things; social intelligence, involved in dealing with other persons; and abstract intelligence, involved in dealing with the relations between ideas. Each of these types of intelligence involves the presence in a high degree of a group of different traits. Thus, in social intelligence, a high degree of sympathy, sensitivity to praise and blame, leadership, and the like, are more requisite than they are for intelligent behavior in the realm of mechanical operations or of mathematical theory. A person may be highly intelligent in one of these three spheres and mentally helpless in the others. Thus, a brilliant philosopher may be nonplused by a stalled motor; a successful executive may be a babe in the realm of abstract ideas. But what we rate as a person's general intelligence is a kind of average struck between his various competences, an estimate of his general ability to control himself in the miscellaneous variety of situations of which his experience consists.

[Footnote 1: "Measuring Intelligence," Harper's Magazine, March, 1920.]

There have been a number of tests devised for the purpose of estimating an individual's general intelligence.[1] On a rating scale such as is used in these examinations most individuals will come up to a certain standard that may be called average or normal. There will be a certain number so far below the normal rating in a complex of traits that go to produce intelligent (competent and facile) behavior that they will have to be classed as subnormal, ranging from feeblemindedness to idiocy. A certain number will be found so extraordinarily gifted in general traits and in specific abilities—in given subject-matters, as, for example, in mathematics and music—that they will be marked out as geniuses. Following the laws of probability, the greater the inferiority or superiority, the more exceptional it will be.

[Footnote 1: These, in large part, deal with words and ideas and are, therefore, weighted in favor of abstract intelligence, and put at a discount individuals whose experience and whose intelligence are predominantly social or mechanical in character. Some of the tests are fairly adequate for mechanical intelligence, but no good tests have been devised for social intelligence. These tests, however, as used in the army and for appraising college entrants, as at Columbia University, have been demonstrated to be fairly good indices of general intelligence.]

Individual differences are, therefore, seen to be not simply differences with respect to given mental traits, but differences with respect to general mental capacity. Experimental investigation points to a graded difference in mental capacity, ranging from idiocy to genius, the largest group being normal or average, the size of the group diminishing with further deviation from the average in either direction.

Certain important correlations, furthermore, have been found between the level of intelligence and the level of character. The great in mind, it may be said briefly, are also great in spirit. "General moral defect commonly involves intellectual inferiority. Woods and Pearson find the correlation between intellect and character to be about .5.... General moral defect is due in part to a generally inferior nervous organization."[1]

[Footnote 1: Thorndike: Educational Psychology (1910), p. 224.]

One other important correlation must be noted. While gifts and capacities are specific, superiority in a given trait commonly involves superiority in most others. Exceptional talent in one direction in most cases involves exceptionality in many other respects. While talents are not indiscriminately transferable from one field to another, the same complex of traits which makes a person stand out preËminently in a given field, say law, would make him stand out in any one of half a dozen different fields into which he might have gone. There seems to be no evidence that extraordinary capacity in one direction is balanced by extraordinary incapacity and stupidity in others. The fact that individuals differ not only in specific traits but in general mental capacity has, also, certain obvious practical consequences. It means that there are present in society, in the light of recent tests in the army, an unexpectedly large number of individuals below the level of normal intelligence. One in five hundred, Thorndike estimates, is the "frequency of intellectual ability so defective as to disturb the home, resist school influence, and excite popular derision." These are clearly liabilities in the social order. On the other hand, there is a large number above the level of average intelligence. The importance of this group for human progress can hardly be overestimated. As we have seen in other connections, progress is contingent upon variation from the "normal" or the accustomed, and such variation from the normal is initiated in the majority of cases by members of this comparatively small super-normal group. If civilization is to advance it must capitalize its intelligence; that is, educate up to the highest point of native ability. But in any case, its chief guarantee of progress lies in the comparatively small group in whom native ability is exceptionally high. For it is among this group that original thinking, invention, and discovery almost exclusively occur.

Causes of individual differences. Among the chief causes of individual differences may, in general, be set down the following: (1) Sex, (2) Race, (3) Near Ancestry or Family, (4) Environment. The particular fund of human nature which an individual displays, that is, his specific native endowments, as they appear in practice, will be a resultant of these various causes. In the study of each of these characteristics, we should be able ideally to eliminate all the others and to consider them each in isolation.

The influence of sex. In the case of sex, for example, we should not confuse individual differences due to the fact of sex with individual differences due to divergent training given to each of the sexes. In scientific experiments to determine sex differences in mental traits, there have been careful attempts to eliminate everything but the factor of sex itself. Thus in Karl Pearson's studies of fifty twin brothers and sisters, the factors of ancestry and difference of training and age were practically eliminated.

In so far as allowance can be made for other contributing factors, studies of individual differences due to sex have revealed, roughly speaking, the following results. There have been, in the field of sensory discrimination and accuracy of motor response, slight—and negligible—differences of responses made by male and female. The subjects stated were, in most cases, selected so far as possible from the same social strata, social and intellectual interest, and background.[1]

[Footnote 1: As, for example, the members of the graduating and junior classes of the co-educational college at the University of Chicago, studied by Dr. Thompson.]

Thorndike reports the general results of such tests as follows:

The percentages of males reaching or exceeding the median ability of females in such traits as have been subjected to exact investigation are roughly as follows:

The most important characteristic of these differences is their small amount. The individual differences within one sex so enormously outweigh the differences between the sexes in these intellectual and semi-intellectual traits that for practical purposes the sex difference may be disregarded. So far as ability goes, there could hardly be a stupider way to get two groups alike within each group but differing between the groups than to take the two sexes. As is well known, the experiments of the past generation in educating women have shown their equal competence in school work of elementary, secondary, and collegiate grade. The present generation's experience is showing the same fact for professional education and business service. The psychologists' measurements lead to the conclusion that this equality of achievement comes from an equality of natural gifts, not from an overstraining of the lesser talents of women.[1]

[Footnote 1: Thorndike: Educational Psychology, briefer course, pp. 345-46.]

That is, so far as experiments upon objectively measurable traits have been conducted, the specific differences that individuals display have comparatively nothing to do with the fact that an individual happens to be a man or a woman. These experiments have been conducted with boys and girls as young as seven, and with men and women ranging up to the age of twenty-five.[2]

[Footnote 2: There seems, as might be expected to be, a slightly higher differentiation between the two sexes after adolescence than before.]

These experiments have been conducted to test sensory discrimination, precision of motor response and some of the simpler types of judgment, such as those involved in the solution of simple puzzles with blocks, matches, etc. The fact of the negligibility of sex difference with regard to certain minor measurable traits has been adequately demonstrated by a wide variety of experiments. The fact of sex equality or mental capacity has been less accurately but fairly universally noted by popular consensus of observation and opinion of the work of women in the various trades and professions. There are differences between men and women in physical strength and in consequent susceptibility to fatigue. These are important considerations in qualifying the amount of work a woman can do as compared with that of a man, and have justly resulted in the regulation of hours for women, as a special class. But there do not seem to be, on the average, significant original differences in mental capacity.[3]

[Footnote 3: On this subject there has been collected a large amount of accurate experimental data. See Goldmark: Fatigue and Efficiency, part II, pp. 1-22. These refer to physiological differences.]

There do exist, as a matter of practical fact, some of the special attributes commonly ascribed to the masculine and feminine mental life, but it is generally agreed by investigators that these are to be accounted for by the different environment and standards socially established for men and for women. There are radical and subtle differences in training to which boys and girls are subjected from early childhood. There are deeply fixed traditions as to the standards of action, feeling, and demeanor to which boys and girls are respectively trained and to which they are expected to conform. If a boy should not live up to this training and expectation, he may be marked out as "effeminate." If a girl does not conform, she is defined as a "hoyden" or a "tomboy."

These social distinctions, which are emphasized even in the behavior of young boys and young girls, grow more pronounced as individuals grow older. One need hardly call attention to actions regarded as perfectly legitimate for men which provoke disapproval if practiced by women. Rigid training in these different codes of behavior may cause acquired characteristics to seem inborn. But whether these general features commonly held to distinguish the mental life of man or woman are or are not intrinsic and original, they have been marked out by certain investigators as socially fundamental. Thus Heymans and Wiersma, two German investigators, set down as the differentia of feminine mental life (1) greater activity, (2) greater emotionality, (3) greater unselfishness of the female.[1]

[Footnote 1: See Thorndike's Educational Psychology (1910), p. 136.]

There are some general differences noted by both layman and psychologist, which, though not subject to quantitative determination, yet seem to differentiate somewhat definitely between feminine and masculine mental activity. These may be set down in general as occurring in the field of emotional susceptibility. Thorndike traces them back to the varying intensity of two human traits earlier discussed: the fighting instinct, relatively much stronger in the male, and the nursing or mothering instinct, much stronger in the female. With this fact are associated important differences in the conduct of men and women in social relations. The maternal instinct is held by some writers, for instance, to be in large measure the basis of altruism, and is closely associated with sensitivity to the needs and desires of others. Thorndike writes:

It has been common to talk of women's dependence. This is, I am sure, only an awkward name for less resentment at mastery. The actual nursing of the young seems likewise to involve equally unreasoning tendencies to pet, coddle, and "do for" others. The existence of these two instincts has been long recognized by literature and common knowledge, but their importance in causing differences in the general activities of the two sexes has not. The fighting instinct is in fact the cause of a very large amount of the world's intellectual endeavor. The financier does not think merely for money, nor the scientist for truth, nor the theologian to save souls. Their intellectual efforts are aimed in great measure to outdo the other man, to subdue nature, to conquer assent. The maternal instinct in its turn is the chief source of woman's superiorities in the moral life. The virtues in which she excels are not so much due to either any general moral superiority or any set of special moral talents as to her original impulses to relieve, comfort, and console.[1]

[Footnote 1: Thorndike: loc. cit., pp. 48-49.]

Ordinary observation reveals, as literature has in general recorded, what Havelock Ellis has called the "greater affectability of the female mind." There is evidenced in many women a singular and immediate responsiveness to other people's emotions, a quick intuition, a precise though non-logical discrimination, which, though shared to some extent by all individuals gifted with sympathy and affection, is a peculiarly feminine quality. Indeed when a man possesses it, it is common to speak of him as possessing "almost a woman's intuition." Such emotional susceptibility is manifested in the higher frequency of emotional instability and emotional outbreaks among women than among men, and the decreased power of inhibition which women have over instinctive and emotional reactions. Further than this, women more than men may be said to qualify their judgments of persons and situations by their emotional reactions to them.

The common suspicion that in general women's abilities are less than those of men has seemed to gain strength from the greater number of geniuses and eminent persons there have been among men than among women. Professor Cattell writes in this connection:

I have spoken throughout of eminent men as we lack in English words including both men and women, but as a matter of fact women do not have an important place on the list. They have in all thirty-two representatives in the thousand. Of these eleven are hereditary sovereigns, and eight are eminent through misfortunes, beauty, or other circumstances. Belles-lettres and fiction—the only department in which woman has accomplished much—give ten names as compared with seventy-two men. Sappho and Joan d'Arc are the only other women on the list. It is noticeable that with the exception of Sappho—a name associated with certain fine fragments—women have not excelled in poetry or art. Yet these are the departments least dependent on environment, and at the same time those in which the environment has been perhaps as favorable to women as to men. Women depart less from the normal than men—a fact that usually holds for the female throughout the animal series; in many closely related species only the male can be readily distinguished.[1]

[Footnote 1: Cattell: "A Statistical Study of Eminent Men," Popular Science Monthly, vol. LXII. pp. 375-77.]

In the facts of higher variability among males, and the hitherto restricted social opportunities provided for women are to be found the chief reasons for the comparatively high achievement of the male sex as compared with the female. But on the average the difference between the two sexes with respect to mental capacity is slight.

The influence of race. A second factor in determining individual differences in mental traits is race. There are certain popular presuppositions as to the inherent differences in the mental activity of different races. The Irishman's wit, the negro's joyousness, the emotionality of the Latin races, the stolidity of the Chinese, are all supposed to be fundamental. And in a sense they are. That is, in the life and culture of these groups, such traits may stand out distinctively. But most psychologists and anthropologists question seriously whether these traits are to be traced to radical differences in racial inheritance. For the most part they seem rather to be the result of radical differences in environment. "Many of the mental similarities of an Indian to Indians and of his differences from Anglo-Saxons disappear, if he happens to be adopted and brought up as an Anglo-Saxon."[1]

[Footnote 1: Thorndike loc. cit., p. 52.]

There have been various experimental studies made to determine how much divergences in the mental activity of different races are determined by differences in racial inheritance. Such experiments have been conducted chiefly upon very simple traits and capacities. The accuracy of sensory response among different races has, for example, been examined. There have proved to be, in regard to these, slight differences in the effectiveness and accuracy of response. There are racial differences in hearing, as tested by the ticking of a watch or clock artificially made. In this test, Papuans, to take an instance, were inferior to Europeans. The sense of touch has been similarly tested, and comparatively negligible differences have been found. In regard to the five senses, their efficiency seems to be about equal in all the races of mankind. The proverbial keenness of vision of the Indian, for example, is found to be due to a superior training in its use, a training made imperative by the conditions of Indian life. In reaction time tests—that is, tests in the speed of simple mental and motor performances—the time consumed in response has been found to be about the same for all races tested. The results have been similar with regard to certain simple processes of judgment or inference:

There are a number of illusions and constant errors of judgment which are well known in the psychological laboratory, and which seem to depend, not on peculiarities of the sense organs, but on quirks and twists in the process of judgment. A few of these have been made the matter of comparative tests, with the result that peoples of widely different cultures are subject to the same errors, and in about the same degree. There is an illusion which occurs when an object, which looks heavier than it is, is lifted by the hand; it then feels, not only lighter than it looks, but even lighter than it really is. The contrast between the look and the feel of the thing plays havoc with the judgment. Women are, on the average, more subject to this illusion than men. The amount of this illusion has been measured in several peoples, and found to be, with one or two exceptions, about the same in all. Certain visual illusions, in which the apparent length or direction of a line is greatly altered by the neighborhood of other lines, have similarly been found present in all races tested, and to about the same degree. As far as they go, these results tend to show that simple sorts of judgment, being subject to the same disturbances, proceed in the same manner among various peoples; so that the similarity of the races in mental processes extends at least one step beyond sensation.[1]

[Footnote 1: Woodworth: "Racial Differences in Mental Traits," Science, New Series, vol. 31, pp. 179-81.]

Professor Woodworth also points out that these simple tests are not adequate to measure general intelligence.

A good test for intelligence would be much appreciated by the comparative psychologist, since, in spite of equal standing in such rudimentary matters as the senses and bodily movement, attention and the simpler sorts of judgment, it might still be that great differences in mental efficiency existed between different groups of men. Probably no single test could do justice to so complex a trait as intelligence. Two important features of intelligent action are quickness in seizing the key to a novel situation, and firmness in limiting activity to the right direction, and suppressing acts which are obviously useless for the purpose in hand. A simple test which calls for these qualities is the so-called "form test." There are a number of blocks of different shapes, and a board with holes to match the blocks. The blocks and board are placed before a person, and he is told to put the blocks in the holes in the shortest possible time. The key to the situation is here the matching of blocks and holes by their shape; and the part of intelligence is to hold firmly to this obvious necessity, wasting no time in trying to force a round block into a square hole. The demand on intelligence certainly seems slight enough; and the test would probably not differentiate between a Newton and you or me; but it does suffice to catch the feeble-minded, the young child, or the chimpanzee, as any of these is likely to fail altogether, or at least to waste much time in random moves and vain efforts. This test was tried on representatives of several races and considerable differences appeared. As between whites, Indians, Eskimos, Ainus, Filipinos, and Singhalese, the average differences were small, and much overlapping occurred. As between these groups, however, and the Igorot and Negrito from the Philippines and a few reputed Pygmies from the Congo, the average differences were great, and the overlapping small.[1]

[Footnote 1: Woodworth: loc. cit., pp. 171-86.]

Equality among races in the various traits that have been measured by psychologists does not imply that common observation is wrong in counting one race as intellectually superior to another. There have, as yet, been no measurements of such general features of social life as energy, self-reliance, inventiveness, and the like. But from indications of experiments already made, these so-called (and for practical purposes genuine) intellectual differences between the individuals of different races must be attributed to differences in environment. Races as races seem to be equally gifted.

Professor Boas points out that civilized investigators traveling among savage tribes commit one serious fallacy in insisting on the inferiority of these primitive peoples. They are said to be irrational, for example, when they are quite logical in their way of dealing with the material which is at their disposal. Without any scientific information available, for example, anthropomorphism, or the tendency to interpret cosmic phenomena in human terms is quite natural and reasonable. Again:

The difference in the mode of thought of primitive man and that of civilized man seems to consist largely in the difference of character of the traditional material with which the new perception associates itself. The instruction given to the child of primitive man is not based on centuries of experimentation, but consists of the crude experience of generations. When a new experience enters the mind of primitive man, the same process which we observe among civilized man brings about an entirely different series of associations, and therefore results in a different type of explanation. A sudden explosion will associate itself in his mind, perhaps, with the tales he has heard in regard to the mythical history of the world, and consequently will be accompanied by superstitious fear. When we recognize that neither among civilized men nor among primitive men the average individual carries to completion the attempt at causal explanation of phenomena, but carries it only so far as to amalgamate it with other previously known facts, we recognize that the result of the whole process depends entirely upon the character of the traditional material.[1]

[Footnote 1: Boas: Mind of Primitive Man, pp. 203-04.]

This may be illustrated by our immediate reactions of pleasure or disgust at customs or ideas that provoke directly opposite reactions among races reared in another tradition.

Again primitive races have been accused of lacking self-control. The fact is that they exhibit self-control about matters which they regard as important, and lack of it in respect to matters which they regard as trivial. "When an Eskimo community is on the point of starvation, and their religious proscriptions forbid them to make use of the seals that are basking on the ice, the amount of self-control of the whole community which restrains them from killing those seals is certainly very great."[2] The case is similar with regard to nearly all the alleged inferiorities of primitive man, his improvidence, unreliability, and the like. In nearly every instance, it has been found that we are holding him to account for not being able to persist in courses of action which do not seem to him, with his training and education, worth persisting in, and for not conforming to standards which, given his background, are meaningless.

[Footnote 2: Ibid. p. 108.]

But if differences in racial attainments are due to differences in environment, it might be said that this itself is testimony to the superiority of the race that has the more complex and exacting environment. This is not by any means clearly the case. The "culture" or civilization which a race exhibits is a very uncertain index of its gifts or its capacities. The culture found in a race is, it may be said without exaggeration, largely a matter of accident or circumstance rather than of heredity.

Some of the environmental causes for differences in culture may he explicitly noted. Any modern culture is the result of interminglings of many different cross-streams and cross-borrowings. Races that have long been isolated as, for example the African negroes, have no possibility of picking up all the acquisitions to which races that intermingle have access. Progress in the developments of arts, sciences, and institutions depends on fortunate individual variations. The smaller the race the less the number of variations possible, including those on the side of what we call genius. Again fortunate variations depend not so much on the general average intellectual capacities of the race as on its variability. So one race may possess a relative superiority of achievement because of its high variability, just as, as we have already pointed out, the greater preËminence of the male sex with regard to intellectual accomplishment is due to the greater number of variations both above and below the norm which it displays. The reasons for variability are again, according to Professor Boas, largely environmental. "We have seen, when a people is descended from a small uniform group, that then its variability will decrease; while on the other hand, when a group has a much-varied origin or when the ancestors belong to entirely distinct types the variability may be considerably increased."[1]

[Footnote 1: Boas; loc. cit., p. 93.]

Again a race may be placed in such geographical conditions that a fortuitous variation on the part of one individual may prove of enormous value in the development of its civilization. Or fortunate geographical conditions may stimulate types of activity that lie dormant, although possible, among other races. Thus by some investigators the flexibility and emancipation of the Greek genius were attributed to their access to the sea and their constant intermingling with other cultures, especially the Egyptian.

On the subject of the fundamental equality of races despite their seeming disparity, as that at present, let us say, between whites and negroes, Professor Boas writes:

Much has been said of the hereditary characteristics of the Jews, of the Gypsies, of the French and Irish, but I do not see that the external and social causes which have moulded the character of members of these people have ever been eliminated satisfactorily; and, moreover, I do not see how this can be accomplished. A number of external factors that influence body and mind may easily be named—climate, nutrition, occupation—but as soon as we enter into a consideration of social factors and mental conditions we are unable to tell definitely what is cause and what is effect.

The conclusions reached are therefore, on the whole, negative. We are not inclined to consider the mental organization of different races of man as differing in fundamental points. Although, therefore, the distribution of faculty among the races of man is far from being known, we can say this much: the average faculty of the white race is found to the same degree in a large proportion of individuals of all other races, and although it is probable that some of these races may not produce as large a proportion of great men as our own race, there is no reason to suppose that they are unable to reach the level of civilization represented by the bulk of our own people.[1]

[Footnote 1: Boas; loc. cit., pp. 116, 123.]

In contrast must be cited the opinions of a large class of psychologists and anthropologists who are inclined to regard racial differences as intrinsic and original. Of such, for example, is Francis Galton, who claims in his Hereditary Genius, that taking negroes on their own ground they still are inferior to Europeans by about one eighth the difference, say, between Aristotle and the lowest idiot. Recent psychological experiments in the army reveal, again, certain fundamental intellectual inferiorities of negroes, though whether this is environmental or to be traced to hereditary causes is open to question.

The fact remains that there are, despite the lack of evidence for hereditary mental differences, practical differences in the mental activity of different races that are of social importance. These differences, which seem so fundamental, have been explained primarily by the powerful control exercised over the individual by the habits which he acquires even before the age of five years. These, though unconscious, may be, as the Freudian psychologists maintain, all the more important for that reason. This would appear to be the only explanation of significant racial differences. Cultural differences cannot, biologists are generally agreed, be transmitted in the germs that pass from generation to generation. One may say, in effect, that an individual is differentiated in his mental traits by early association with a certain race, and by his immediate ancestry or family, rather than by the fact of belonging physically to a certain race.

The influence of immediate ancestry or family. A factor that is, on experimental evidence, rated to be of high importance in the determination of the differences of the mental make-up of human beings, is "immediate ancestry" or family. Stated in the most simple and general terms this means that children of the same parents tend to display marked likenesses in mental traits, and to exhibit less variation among themselves than is exhibited in the same number of individuals chosen at random. A great number of experiments have been conducted to determine how far resemblances in mental traits are due to common parentage. The correlation between membership in the same family and resemblances of social traits has been found to be uniformly high.

The inference was made that children of the same family would show great resemblances in mental traits, when accurate experiments showed marked similarity in physical traits under the same conditions. The coefficient of correlation between brothers in the color of the eye, is, according to the results obtained by Karl Pearson, .52.[1] The coefficient of fraternal correlation in the case of the cephalic index (ratio of width to length of head) is .40. The correlation of hair color is found to be .55. The fact of high correlation between resemblance of physical traits and membership in the same family is of crucial importance, because these traits are clearly due to ancestry, and not to environmental differences. If physical traits show such a correlation, it is likely that mental traits will also, mental traits being ultimately dependent on the brain and the nervous system, which are both affected by ancestry.

[Footnote 1: These facts are based on the reports of Karl Pearson in his On the Laws of Inheritance in Man. What is meant by coefficient of correlation may be explained as follows: If the coefficient of correlation between father and son is .3 and the coefficient of correlation between brother and brother is .5 we may say: a son on the average deviates from the general trend of the population by .3 of the amount of his father's deviation, a brother by .5 of the amount of his brother.]

Measurements of measurable traits and observations of less objectively measurable ones, have revealed that immediate ancestry is in itself an influential factor in producing likenesses and differences among men with respect to mental traits. One interesting case, interesting because it was a test of a capacity that might be expected to be largely environmental in its origins, was that of the spelling abilities of children in the St. Xavier School in New York. Thorndike thus reports the test:

As the children of this school commonly enter at a very early age, and as the staff and the methods of teaching remain very constant, we have in the case of the 180 brothers and sisters included in the 600 children closely similar school training. Mr. Earle measured the ability of any individual by his deviation from the average for his grade and sex, and found the co-efficient of correlation between children of the same family to be .50. That is, any individual is on the average fifty per cent as much above or below the average for his age and sex as his brother or sister.

Similarities in home training might theoretically account for this, but any one experienced in teaching will hesitate to attribute much efficacy to such similarities. Bad spellers remain bad spellers though their teachers change. Moreover, Dr. J. M. Rice in his exhaustive study of spelling ability found little or no relationship between good spelling and any one of the popular methods, and little or none between poor spelling and foreign parentage. Yet the training of a home where parents do not read or spell the language well must be a home of relatively poor training for spelling. Cornman's more careful study of spelling supports the view that ability to spell is little influenced by such differences in school or home training as commonly exist.[1]

[Footnote 1: Thorndike: loc. cit., p. 78.]

In general the influence of heredity may be said far to outweigh the influence of home training. In all the cases reported, the resemblances were about the same in traits subject to training, and in those not subject to training. Thus industry and conscientiousness and public spirit, which are clearly affected by environment, show no greater resemblance than such practically unmodifiable traits as memory, original sensitiveness to colors, sounds, and distances.

The influence of parentage, it must be added, consists in the transmission of specific traits, not of a certain "nature" as a whole. There are in the germ and the ovum which constitute the inheritance of each individual, certain determinant elements. The elements that determine the original traits with which each individual will be born vary, of course, in the germs produced by a single parent less than among individuals chosen at random, but they vary none the less. In this variation of the determining elements in the germs of the same individual is to be found the cause of the variation in the physical and mental traits among children of the same parents.

Since the determining elements, the unit characters that appear in the sperm or ovum of each individual, do not appear uniformly even in children of the same parents, brother and sister may resemble each other in certain mental traits, and differ in others. "A pair of twins may be indistinguishable in eye color and stature, but be notably different in hair color and tests of intellect."

Mental inheritance, as well as physical, is, then, organized in detail. It is not the inheritance of gross total natures, but of particular "mental traits." If we had sufficient data, we should be able to analyze out the unit characters of an individual's mental equipment, so as to be able to predict with some accuracy the mental inheritance of the children of any two parents. In the case of physical inheritance, the laws of the hereditary transmission of any given traits are known in considerable detail. The detailed quantitative investigations of inheritance, following the general lines set by Mendel, have given striking results.

Physical traits have been found to be analyzable into unit-characters (that is, traits hereditarily transmitted as units), such as "curliness of hair," "blue eyes," and the like. Mental traits, however, do not seem analyzable into the fixed unit-characters prescribed by the Mendelian laws of inheritance.

The success which breeders have had in the control of the reproduction of plants and animals, in the perpetuation of a stock of desirable characteristics and the elimination of the undesirable, has given rise to a somewhat analogous ideal in human reproduction. That eugenics has at least its theoretical possibilities with regard to physical traits, few biologists will question. However difficult it may be in practice to regulate human matings on the exclusive basis of the kind of offspring desired, it is a genuine biological possibility. In a negative way, it has already in part been initiated in the prevention of the marriage of some extreme types of the physically unfit, by the so-called eugenic marriage laws in some states in this country.[1]

[Footnote 1: There have been laws, as there is a fairly decided public opinion, adverse to reproduction by the feeble-minded and the morally defective. But (see Richardson: The Etiology of Arrested Mental Development, p. 9) there have been a number of cases of feeble-minded parents producing normal children.]

But whether scientific regulation of marriages for the production of eugenic offspring is feasible, even apart from the personal and emotional questions involved, is open to question. No mental trait such as vivacity, musical ability, mathematical talent, or artistic sense, has been analyzed into such definitely transmissible unit-characters as "blue eyes" and "curliness of hair." So many unit-characters seem to be involved in any single mental trait that it will be long before a complete analysis of the hereditary invariable determinants of any single trait can be made.

It is thus impossible to tell as yet with any security or precision the biological components of any single mental trait. The evidence at our disposal, however, does confirm us in the belief that one of the most significant and certain causes of individual differences, whether physical or mental, is immediate ancestry or family. Individuals are made by what they are initially, and, as we shall presently see, therefore largely by their inheritance. With the latter, environment can do just so much, and no more. And the most significant and effective part of an individual's inheritance is his family for some generations back, rather than the race to which he belongs.

The influence of the environment. Those factors so far discussed which determine individual differences are independent of the particular conditions of life in which an individual happens to be placed. An individual's race, sex, family are beyond modification by anything that happens to him after birth. Maturity, in so far as it is mere growth independent of training, is also largely a fixed and unmodifiable condition.

The original nature, determined by race, sex, and immediate ancestry, with which a man starts life is subject to modification by his social environment, by the ideas, customs, companions, beliefs, by which he is surrounded, and with which he comes continuously in contact. Commonly the influence of environment is held to be very high. It is difficult, however, accurately to distinguish between effects which are due to original nature and effects which are due to environment.

Differences in training are important, but the results vary with the natures trained. Precisely the same environment will not have the same consequences for two different natures. Two approximately same natures will show something like the same effects in dissimilar environments. Human beings are certainly differentiated by the customs, laws, ideals, friends, and occupations to which they are exposed. But what the net result will be in a specific case, depends on the individual's equipment to start with, an equipment that is fixed before the environment has had a chance to act at all. The kindliness and indulgence that save some children demoralize others. In some people a soft answer turneth away wrath; in others it will kindle it. Andrew Carnegie starts as a bobbin boy, and becomes a millionaire; but there were many other bobbin boys. The sunset that stirs in one man a lyric, leaves another cold. The same course in biology arouses in one student a passion for a life of science; it leaves another hoping never to see a microscope again. On the other hand, the same types of original capacity thrown into different environments will yet attain somewhat comparable results, in the way of character and achievement. The biographies of a few poets, painters, philosophers, and scientists chosen at random, show the most diverse antecedents.[1]

[Footnote 1: Taking the social and professional status of a distinguished man's father as some index of the social environment to which he was subjected during his youth, we find some interesting examples: The father of John Keats was a livery stable-keep; his mother the daughter of one. Byron's father was a captain in the Royal Guards; his mother a Scottish heiress. Newton's father was a tanner; Pasteur's, a tanner; Darwin's, a doctor of considerable means. Francis Bacon's father was Lord Keeper of the Great Seal; Newton's was a farmer and the headmaster of a school; Turner was the son of a barber.]

An individual, again, to a certain extent, makes his own environment. What kind of an environment he will make depends on the kinds of capacities and interests he has to start with. Similarity of original tendencies and interests brings men together as differences among these keep them apart. The libraries, the theaters, and the baseball parks are all equally possible and accessible features of their environment to individuals of a given economic or social class. Yet a hundred individuals with the same education and social opportunities will make themselves by choice a hundred different environments. They will select, even from the same physical environment, different aspects. The Grand CaÑon is a different environment to the artist and to the geologist; a crowd of people at an amusement park constitutes a different environment to the man who has come out to make psychological observations, and the man who has come out for a day's fun. A dozen men, teachers and students, selected at random on a university campus, might well be expected to note largely different though overlapping facts, as the most significant features of the life of the university.

The environment is the less important in the moulding of character, the less fixed and unavoidable it becomes. If an individual has the chance to change his environment to suit his own original demands and interests, these are the less likely to undergo modification. This is illustrated in the animal world by the migratory birds, which change their habitations with the seasons. Similarly human beings, to suit the original mental traits with which they are endowed, can and do exchange one environment for another. There are a very large number of individuals living in New York City, in the twentieth century, for example, for whom a multiplicity of environments are possible. The one that becomes habitual with an individual is a matter of his own free choice. That is, it is choice, in the sense that it is independent of the circumstances of the individual's life. But an individual's choice of his environment must be within the limited number of alternatives made possible by the original nature with which he is endowed. As pointed out in connection with our discussion of "Instinctive Behavior," we do originally what gives satisfaction to our native impulses, and avoid what irritates and frustrates them. We may be trained to find satisfactions in acquired activities, but there is a strong tendency to acquire habits that "chime in," as it were, with the tendencies we have to start with.

There is, for example, to certain individuals, intrinsic satisfaction in form and color; to others in sound. To the former, pictures and paintings will tend to be the environment selected; to the latter the hearing and the playing of music. To those gifted with sensitivity in neither of these directions, pictures may be through all their lives a bore, and a piano a positive nuisance.

These facts of original nature, therefore, determine initially, and consequently in large part, what our environment is going to be. Once we get into, or select through instinctive desires, a certain kind of environment, those desires become strengthened through habit, and that environment becomes fixed through fulfilling those habitual desires. A man may, in the first place, choose artists or scholars as companions because his own gifts and interests are similar. But such an environment will become the more indispensable for him when it has the reinforcement of habit to confirm what is already initially strong in him by birth. "To him who hath shall be given" is most distinctly true of the opportunities and environment open to those with native gifts to begin with.

Original nature thus sets the scope and the limits of an individual's character and achievement. It tells "how much" and, in the most general way, "what" his capacities are. Thus a man born with a normal vocal apparatus can speak; a man born with normal vision can see. But what language he shall speak, and what sights he shall see, depend on the social and geographical situation in which he happens to be placed. Again, if a man is born with a "high general intelligence," that is, with keen sensory discriminations and motor responses, precise and accurate powers of analysis of judgment, a capacity for the quick and effective acquisition and modification of habits, we can safely predict that he will excel in some direction. But whether he will stand out as a lawyer, doctor, philosopher, poet, or executive, it is almost impossible from original nature to tell.[1]

[Footnote 1: The psychological tests used in the army, and being used now with modifications in the admission of students to Columbia College, are "general intelligence" tests. That is, they show general alertness and intellectual promise, but are not prophetic of any specialized talents or capacities.]

Individual differences—Democracy and education. The fact that individuals differ in ability and interest has important consequences for education and social progress. It means, in the first place, that while current optimistic doctrines about the modifiability of human nature are true, they are true within limits—limits that vary with the individual. Whether or not we shall ever succeed, through the science or the practice of eugenics, in eliminating low ability and perpetuating high exclusively, the fact remains that there are in contemporary society the widest variations both in the kinds of interest and ability displayed, and in their relative efficacy under present social and industrial conditions.

There are, it must be noted at the outset, a not inconsiderable number of individuals who must be set down as absolute social liabilities. Even if existing social and educational arrangements were perfect, these would remain unaffected and unavailable for any useful purpose. They would have to be endowed, cared for, or confined. There is the quite considerable class, who, while normal with respect to sensory and motor discrimination, seem to be seriously and irremediably defective in their powers of judgment. These also seem to offer invulnerable resistance to education, and their original natures would not be subject to modification even by an education perfectly adapted to the needs of normal people.

But the more significant fact, more significant because it affects so many, is the fact that within the ranks of the great class of normal people, there are fundamental inherited differences in ability and interest. Next in importance to the fact that an individual is human is the fact that he is an individual, with very specific initial capacities and desires. For education the implications are serious. Education aims, among other things, to give the individual habits that will enable him to deal most effectively with his environment. But an individual can be trained best, it goes without saying, in the capacities and interests he has to begin with. Education cannot, therefore, be wholesale in its methods. It must be so adjusted as to utilize and make the most of the multifarious variety of native abilities and interests which individuals display. If it does not utilize these, and instead sets up arbitrary moulds to which individuals must conform, it will be crushing and distorting the specific native activities which are the only raw material it has to work upon.

There have not as yet been many detailed quantitative studies of individual differences that would enable educators, if they were free to do so, scientifically to adapt education to specific needs and possibilities. Beginnings in this direction are being made, though rather in advanced than in more elementary education. Professional and trade schools, and group-electives in college courses are attempts in this direction. Any attempt, of course, to adapt education to specific needs and interests, instead of crushing them into a priori moulds, requires, of course, a wider social recognition and support of education than is at present common. For individual differences require attention. And where millions are to be educated, individual attention requires an immense investment in teaching personnel.

But in this utilization of original interests and capacities lies the only possibility of genuinely effective education.[1] In the first place to try in education to give individuals habits for which they have no special innate tendencies to begin with, is costly. Secondly, to train individuals for types of life or work for which their gifts and desires are ill adapted is to promote at once inefficiency and unhappiness. One reason why the chance to identify one's life with one's work (as is the case with the artist and the scholar) is so universally recognized as good fortune, is because it is so rare. A general and indiscriminate training of men, as if they were all fitted with the same talents and the same longings, does as much as underpayment or overwork to impair the quality of the work done and the satisfaction derived from it.

[Footnote 1: A beginning in the application of this principle has been made by the vocational guidance and employment management work which is being done with increasing scientific accuracy throughout the United States. Individual differences and interests are studied with a view to putting "the right man in the right place." This slogan is borrowed from the Committee on Classification and Personnel, which during the Great War, through its trade tests and other machinery of differentiation, utilized for the national welfare the specific abilities of thousands of drafted men.]

It has latterly been recognized that industry offers the crucial opportunity to utilize to the fullest individual differences. By "getting the right man in the right place," we at once get the work done better and make the man better satisfied. If adequate attention is given to "placement," to the specific demands put upon men by specific types of work, and to the specific capacities of individuals for fulfilling those demands, we will be capitalizing variations among men instead of being handicapped by them. As it is, specific differences do exist, and men enter occupations and professions ignoring them. As a result both the job and the man suffer; the former is done poorly, and the latter is unsuccessful and unhappy.

It must be noted that the existence of specific differences between individuals does not altogether, or often even in part, imply superiority or inferiority. It implies in each case inferiority or superiority with respect to the performance of a particular type of work. Whether scientific insight and accuracy is better than musical skill, whether a gift for salesmanship surpasses a gift for mathematics, depends on the social situation and the standards that happen to be current among the group. An intensely disagreeable person may be the best man for a particular job. All scientific observation can do is to note individual differences, to note what work makes demands upon what capacities, and try to bring the man and the job together.

It must be emphasized that, while individual capacities determine what an individual can do, social ideals and traditions determine what he will do, because they determine what he will be rewarded and encouraged to do. There is no question but that in our industrial civilization certain types of ability, that of the organizer, for example, have a high social value. There is no question but that there are other abilities, which under our present customs and ideals we reward possibly beyond their merit, as, to take an extreme case, that of a championship prize fighter. We can through education and vocational guidance utilize all native capacities. To make provision for the utilization of all native capacities is to have an efficient social life. But to what end our efficient human machinery shall be used depends on the ideals and customs and purposes that happen to be current in the social order at any given time.

In the words of Professor Thorndike, "we can invest in profitable enterprises the capital nature provides." But what profiteth a man or a society, is a matter for reflective determination; it is not settled for us, as are our limitations, at birth.

The net result of scientific observation in this field is the discovery, in increasingly precise and specific form, that men are most diverse and unequal in interest and capacity. The ideal of equality comes to mean, under scientific analysis, equality of opportunity, leveling all social inequalities; the fact of natural inequalities and divergences remains incontestable.

There may even be, as recent psychological tests seem to indicate, a certain proportion of individuals who are not competent to take an intelligent part in democratic government, who, having too little intellectual ability to follow the simplest problem needing coÖperative and collective decision, must eternally be governed by others. If these facts come to be authenticated by further data, it merely emphasizes the fact that in a country professedly democratic it is essential to devise an education that will, in the case of each individual, educate up to the highest point of native ability.

Where a country is ostensibly democratic, a few informed citizens will govern the many uninformed, unless the latter are educated to an intelligent knowledge and appreciation of their political duties and obligations. Furthermore, the citizens of a community who are prevented from using their native gifts will be both useless and unhappy. Certainly this is an undesirable condition in a society where all individuals are expected, so far as possible, to be ends in themselves and not merely means for the ends of others.