Individual Differences: The Galton-Pearson Approach
Frank H. Hankins
FROM the beginning of the modern democratic movement the doctrine of an inherent equality among men has been persistent. While the assertion that "all men are created equal" as set forth in the famous Declaration has not been taken literally by the majority of informed writers, it has, nevertheless, been held by many as a fundamental article of faith. As such it has been ill-defined; facts obviously in conflict with it have been passed over in silence or in scorn. Being considered essential to the ideals of democracy, it has been, like other doctrines which are fervently avowed with the weighty emotional values of religious mysticism, immune to criticism. Its constant reiteration has been the chief evidence of its patent validity.
Even among men of scientific and philosophical training, especially in the United States, a deeply grounded faith in democracy has carried with it belief in the essential equality of men. The doctrine, semi-religious in itself, has had a powerful religious sanction in the Christian hope of human brotherhood. Consequently, under its impulsion have developed many of the most characteristic
( 273) features of present civilization. The suffrage has been made universal; even the immemorial prejudice of sex inferiority dissolved before the mystical potency of egalitarian ideas. In fact, not a few of the more hysterical and visionary feminists seemed to picture in a rather nebulous form a coming millennial state in which woman would be at last "free and equal," enjoying not merely civil and political equality, not merely economic equality and hence freedom from male domination, but also a sort of undefined biological freedom and equality, a state in which babies would be secured by adoption or from incubators and reared by motherless nurseries.
The doctrine of equality has been a potent factor in the development of the American scheme of popular education. There probably is no more widespread illusion in this country than that any one by effort and education can reach any level in the economic or social scale. There certainly is no doctrine more dear to the popular mind, nor one more productive of preferment for the petty politician or of "filthy lucre" for the professional inspirationalist who "cures" the office boy, the clerk, the tired business man and the "disappointed in love" of one set of illusions by creating another. This is not to question the value of popular education or of illusions. To destroy the one would be to extract from American life much of its vim and resourcefulness; and to destroy the other would leave many an individual hesitant and spiritless. Moreover, we have definitely entered upon an elaboration and diversification of facilitiesfor popular education which will actually enlarge opportunity through adaptation of training to individual bent and capacity.
The doctrine is equally potent in the field of economics and social reform. Itis a vital center of a large part of the propaganda of socialism and communism. The chief evils of the present order are popularly considered to be the inequalities of income and standards of life with the consequent exploitation of the poor by the rich, the weak by the strong. Hence the vast majority of programs for social improvement are imbued with ideas of equalization of opportunity, of income, of wealth, of work or of responsibility and directing authority. Much of this, like the feminism of W. L. George and his ilk, is a sort of group "flight from reality," an escape from the dreadfully pressing and embittering facts of human inequality. The fine-spirited, broad-minded humanist joins hands and hearts with the plodding worker in dreaming of a proletarian millenium in which work will be less in quantity and more equal in distribution, while pay will be greater in quantity and also more equally shared by all. But in spite of popular education, in spite of universal suffrage, in spite of labor legislation with its eight-hour day and minimum wage, in spite of labor parties and the socialist vote the inequalities of social life have persisted.
The educational statistics reveal how grossly unequal the educational attainment is, even in the purest American communities. Of the hordes who enter the schools, vast troops drop out at the fourth, fifth, sixth and eighth grades, leaving a small residuum for the high-school and a still smaller body for the college. The statistics of wealth
( 274) and income indicate that a favored few own most of the wealth and take an undue share of the income, while "the masses" own next to nothing and receive less than a "decent American standard of living" requires. Conditions are even worse, that is, more unequal in these respects in Great Britain, France, Germany, Italy and elsewhere. We are shocked to learn that even in the administration of justice there is a fatal lack of equality, especially as between rich and poor, while the social observer must be struck with the varying capacities of men, women and children to utilize, to enjoy, to exploit whatever environmental opportunity or whatever event with which they come in contact. One thus realizes that liberty and justice, even education and opportunity, are not merely objective and institutional in basis and character, but are in their concrete realization closely correlated with the qualities of the individual personality.
Now, the exact quantitative study of individual differences may be said to have begun in the researches of Adolf Quetelet, the founder of modern anthropometry. His earliest studies revealed the symmetrical distribution of measurements of height and chest circumferences about the average dimensions of a somewhat imaginary "average man" (l'homme moyen). He later made extended measurements on persons of all ages and thus elaborated a "law of growth" for the average or typical person of an extended group, an average from which there were characteristic variations after the manner of the law of distribution of chances. He also made some suggestive beginnings in the measurement of individual differences in their mental and moral activities.
The development of Quetelet's ideas are readily traced. In his first and greatest work outside the field of astronomy, Sur l'homme et le développement de ses facultés, un essai de physique sociale (2 vols., Paris, 1835) he summarized a number of his own studies and a considerable quantity of others relating to the physical and mental qualities of man. As he says in the "Preface"of Du Système social et des lois qui le régissent (Paris, 1848) he at that time (i.e. 1835) considered the" average man" merely as the mean between two limits. In the Lettres stir la théorie des probabilités appliquée aux sciences morales et politiques (Brussels, 1846) he conceived the "average man"as to height to be the mean about which the heights of men are grouped according to the law of accidental causes.But in du Système he showed "that the law of accidental causes is a general law which dominates our moral and intellectual qualities as well as our physical qualities." Thereafter Quetelet made some additional researches on human conduct and numerous ones on the height,weight and bodily proportions at various ages. These formed the basis of his Anthropométrie ou mesure des différentes facultés de l'homme (Brussels, 1870). In this he made use of a very considerable accumulation of anthropometrical data including such notable studies as those of Samuel Brown on soldiers and civilians in England and Scotland, the statistical investigations of Wagner, von Oettingen, Wappaeus and Held in Germany and Bodio in Italy, and the memorable Investigatians in the Military and Anthropological Statistics of American Soldiers by B. A. Gould, published in 1869. In Quetelet, therefore, we find the beginnings of those statistical studies which have grown into the quantitative study of biological variation and mental and moral differentiation in man. He clearly demonstrated not only that men differ one from
( 275) another but gave precision to our ideas as to the form in which the differences are distributed through a group.
The next stride was made by Francis Galton, who acknowledged his debt to Quetelet. Galton's work is, in fact, the main fountainhead for the varied streams of statistical measurements of individual differences in biology, psychology and education. He began with Quetelet's conception of the average and of the distribution around it and made these ideas fundamental in all reasoning regarding social, psychological and biological phenomena. His scientific interests were varied, but from first to last he showed great interest in the relative importance of heredity and environment in producing differences of personality and achievement. He repeatedly attacked this problem in various ingenious ways but notably from the standpoint of the superior men of a group. From his very first essay in this field, "Hereditary Talent and Character" (Macmillan's Magazine, 1865) Galton was moved by a strong belief in the importance of racial quality for social welfare and national achievement. He never lost sight of the practical aim to improve the hereditary stock of the nation. Doubtless his greatest contributions to science were his manifold improvements and inventions in the field of method; but his devising of methods was always subsidiary to the purpose of solving some fresh approach" to problems directly or remotely related to his life theme. In this first essay he noted the ease with which animal breeders mold the qualities of the various domestic breeds; and called attention to the complete absence of any thought as to similar possibilities of improving the human stock. He rejected the current notion that the sons of distinguished men are in general below average capacity. One may recall here the still popular notions that the sons of ministers turn out badly, and that the sons of the well-to-do are so shiftless that "there are three generations from shirt sleeves to shirt sleeves." Galton cited numerous instances of the perpetuation of superiority in families. He thought great advances in national culture would follow the marriage of superior men and superior women and even suggested the endowment of a half-score marriages of couples selected for pre-eminent fitness. This essay is a prolegomenon for the more pretentious works which followed.
The first of these, Hereditary Genius (1869) deserves rank along side the Origin of Species as a contribution to science. In the "Preface" he points out that he is "the first to treat the subject (inheritance of ability) in a statistical manner, to arrive at numerical results and to introduce the 'law of deviation from the average' into discussions on heredity," That Darwin was much impressed with this work is shown by his frequent citations from it in The Descent of Man and by a letter to Galton in which he said: "You have made a convert of an opponent in one sense, for I have always maintained that, excepting fools, men did not differ much in intellect, only in zeal and hard work." Much progress has been made in the succeeding half-century, but there is still a vast company who hold to Darwin's earlier view that men differ little in natural abilities and that genius is only another name for great industry. It should be added, however, that few now believe what many believed in 1869, namely, that heredity has nothing to do with human traits. Galton's writings have done perhaps more than those of any one else to demonstrate the applicability of the laws of inheritance to man, especially to his mental and character traits.
This first great work of Galton's is a
( 276) landmark in the history of biological and sociological sciences. It is the beginning of biometry as a branch of biology; it is a notable contribution to scientific method in all sciences dealing with life; it was the first direct and epochal attempt at the solution of what is in many ways the fundamental problem of practical sociology, namely, the determination of the relative importance of biological and social factors in the determination of the social rank and achievement of individuals. With a wealth of data and precision of method he demonstrated beyond peradventure of doubt that superior ability runs in families, due primarily to the force of heredity. This proposition he supported by a bookful of pedigrees of judges, statesmen, the peerage, military leaders, and outstanding contributors to science, literature, music, painting, poetry, religion, the senior classics at Cambridge and athletics. In the "Preface" to the edition of 1891 he expressed regret at the choice of title because the hereditary genius he was studying was not the highly specialized talent commonly designated as genius. He himself substituted the term "natural ability" by which he meant what now figures in many discussions as general intelligence.
He works out a scale for the distribution of natural ability based directly on the law of chances as applied by Quetelet to physical traits. From an extensive study of biographies and a statistical analysis he concluded that Great Britain had had about 150 "eminent" men in each 1,000,000 males over fifty years of age. The term "eminent" here is far from precise, though not wholly lacking in objectivity for it includes the select portion of those whose names were included in Men of the Time. In a scale of abilities having seven or more grades either side of the median, these 250 "eminent" were all above the fifth grade on the "superior" side. In the same scale 836,000 out of each million were included equally in the two grades above and the two grades below the median. Slightly more than one-half of each million were in the two middle grades. If one add to these two grades the next three grades on the inferior side one achieves a total of 754,110 in each million who may be said to constitute Galton's conception of the masses,"or "the democracy."Above them would be two grades constituting "the middle class" layers and aggregating about 11 per cent of the total. There would remain somewhat less than 3 per cent for "the upper classes." This was an early and admittedly rough estimate; it will be interesting later to compare it with more recent ones.
In the chapter on "Influences that Affect the Natural Ability of Nations" he discussed very cogently the differences in the social value of different family strains. He condemned the cloisters of the middle ages and the current celibacy of university men as tending to eliminate peaceful and refined moral types and strains possessing superior intelligence. In The Comparative Worth of Different Races he inferred that the population of Athens, 530 to 430 B.C., was one or two grades higher than that of modern England and produced "eminent"men ten to seventeen times as frequently. He added that, owing to the increasing complexity of modern civilization a higher type of ability will be required not merely to carry on our institutions but especially to maintain continued progress.
In another interesting section he calculated the differences in the relative contribution to succeeding generations of couples marrying at age twenty-two in contrast with those marrying at age thirty-three; an idea later given great practical and theoretical significance by Professor Karl Pearson under
( 277) the term, genetic or reproductive selection (See Grammar of Science, London, 1900, p. 439) or more recently and popularly, "differential birthrates."Stocks that marry early have (1) more generations alive at any given time; (2) more generations in a century; and (3) more offspring in each generation. Galton here suggested the early marriages of the superior types. This is a logical suggestion as a means of preserving and elevating racial quality, but it is nevertheless paradoxical. Malthus found prudence, as shown by late marriage and small families, a mark of the superior elements in a population. Galton's proposal in the terms of Malthus would mean that the prudent should marry early and have numerous offspring, which amounts to a negation of prudence, and hence of the marks of superiority. Finally, considerable attention is given to questions of method, a matter in which Galton revealed remarkable ingenuity.
The Hereditary Genius is, therefore, a harbinger of Galton's numerous subsequent contributions. His great interest in the worth of different strains of blood in the population became his dominant practical interest. In an essay on "Hereditary Improvement" (Frazer's Magazine, January, 1873) he developed a theory of "viriculture"or the improvement of the breed without offense to moral feelings by the cultivation of a "sentiment of caste." He here suggested the organization of a society for continuous study of the facts of human heredity and variation, an idea later realized in the founding of the Eugenics Laboratory and the Eugenics Education Society.
In the next year he published English Men of Science: their Nature and Nurture (1874) summarizing the one hundred replies he had received to an elaborate questionnaire sent to one hundred and eighty scientific men. He was stimulated to this by Alphonse de CandolIe's Histoire des sciences et des savants, depuis deux siecles. The latter was in itself a sort of rejoinder to Hereditary Genius, being also a study of eminent men. De Candolle attributed little weight to heredity–except in the case of mathematicians; he criticized Galton's views as extreme and found the chief causes of eminence in education, home training and parental stimulation. In a review of the Histoire des sciences ("On the Causes Which Operate to Produce Scientific Men, Fortnightly Review, March 1, 1873) Galton sought to show that de Candolle had unwittingly shown the importance of heredity. Of his own English Men of Science he said in the preface that it strengthened the utmost claims he had ever made for the importance of the hereditary influences.
Nine years later appeared Inquiries into Human Faculty and Its Development (1883). It is clear that men vary in physical traits and that these variations tend to be inherited,—is the same true of mental and moral traits? This extremely ingenious and suggestive work is of considerable significance in the history ofmental measurement and experimental psychology. In addition to a study of the distribution of complexion in the British population and composite portraiture of the criminal, the tubercular, the imbecile, etc., there are studies of energy, sensitivity, weight discrimination, powers of hearing, color blindness, mental imagery, gregariousness, various likes and antipathies, number forms, color associations, visions and hallucinations, effects of early education and training, and various psychometric experiments. Some of his conclusions are of great interest here: he finds evidence of changes in complexion and features of the British population between the days of Holbein
( 278) (1497-1543) and 1880; he concludes that the average height of Englishmen in citieshas declined, and that town life is injurious to fertility; he thinks good nurture tends to increase height; energy "is eminently transmissible by descent" and "in any scheme of eugenics energy is the most important quality to consider"; the most intellectual classes are gifted with the best perceptive powers, idiots lack keen senses, the blind do not excel the seeing nor the savage the civilized in sense powers. He again recurs to the relative contributions to population from early as contrasted with late marriages; and suggests that prizes and marks of merit might serve as a basis for practical eugenics.
Not the least significant section of this work is that on the History of Twins (pp. 155-173 in Everyman's Library edition). Twins are either "similar" ("identical") or "dissimilar" ("non-identical") and they have had either similar or dissimilar nurture. Galton finds that similar nurture does little to make dissimilar twins alike, while dissimilarity of training and experience scarcely affects the identity of twins that are similar.
The impression that all this evidence leaves on the mind is one of some wander whether nurture can do anything at all, beyond giving instruction and professional training. . . There is no escape from the conclusion that nature prevails enormously over nurture when the differences of nurture do not exceed what is commonly to be found among persons of the same rank of society and in the same country (p. 172).
While admitting some effects from early impressions he very penetratingly remarks:
Those teachings that conform to the natural aptitudes of the child leave much more enduring marks than others. Now both the teachings and the natural aptitudes of the child are usually derived from the parents . . . The marks left on the memory by the instructions of a foster-mother are soon sponged clean away. Consider the history of the cuckoo, which is reared exclusively by foster-mothersBut the cuckoo cannot or will not adopt that language (chirp or twitter), or any ocher of the habits of its foster-parents (p. 173).
Here is a point that is almost uniformly neglected in the vast literature that has now grown up on the question of the relative force of heredity and environment in causing individual differences. Observation warrants the statement that versatile human nature utilizes those elements of its environment which "interest" it and that which interests is in some subtle way correlated with the innate pre-dispositions of the organism. In every aspect of life different children like different things, whether it be a question of food, play, adventure or study. The result is that from every kind of environment come the same types of personality with great similarity in achievement; while from very similar environments come every variety of personality with totally different life careers.
Two other sections have a bearing on the problem before us, namely, "Gregariousness and Slavish Instincts," (ibid., 47-57) and "Domestication of Animals" (ibid., 173-194). He thinks gregariousness in man as in Damara cattle is due to natural selection and that from it spring the general slavishness of human nature, the lack of individual independence, and the fickleness of groups and nations due tothe tremendous power of suggestion by
( 279) newspaper and politician. He thinks that this "hereditary taint will have to be bred out of it (our race) before our descendants can rise to the position of free members of an intelligent society." In other words, the mass of men constitute "a mob of slaves, clinging to one another through fear, and for the most part incapable of self-government, and begging to be led" (55).
Such sentiments are doubtless not pleasing to the eulogists of democracy but they present a recognizable portrait of almost any modern nation in a critical situation. But is there not here revealed one of the unsolvable dilemmas of political organization? Because of his gregariousness and his consequent suggestibility man "runs with the herd," or as the French say, "howls with the wolves;" he is made the victim of his own highest emotions and sacrifices himself for mystical, mythical or magical purposes on the altars of religion or patriotism. On the other hand, this suggestibility rendering him sensitive to the opinion of others makes him a moral creature amenable to the laws and ethical rules of his group. In other words a nation of Galton's "strong, self-reliant men" (ibid., 55) might well prove lawless to an extreme and lacking in that capacity for discipline and cohesiveness which seems essential for group defense. Capacity to think for oneself is found only in a limited few, while fearless independence and self-reliance are even rarer in a complex civilization. Timidity and a sense of dependence on his fellows are essential traits of a herd animal. In order that an intricate social order may be workable at all it is essential that the vast majority be ruled by habit and sentiment. It is true as Alexander Meikeljohn has frequently informed us that the American public is a mob and must be educated.
But it is not frequently noted that the utmost education can do is to change the sentiments to which the mob reacts. It cannot change the inherent tendency of the average man to react with the crowd.
The section on the "Domestication of Animals" (ibid., 173-194) points out that doubtless, sometime, somewhere, every sort of animal has been a savage's pet, and yet out of the vast array of species only afew are capable of domestication. Existence in a human environment even for several generations has apparently not the slightest effect on their hereditary natures. Professor Pearson has used a similar figure in his essay on "National Life from the Standpoint of Science" (London, 1901) in which he raises the question as to how and how alone can a wolf be changed to a dog and answers "by selective breeding." An advanced culture is for man much what domestication is for animals. But the North American Indian takes most unkindly to civilization while vagabondage, crime, labor unrest and most of the savage brutality of man to man are evidences of the extreme difficulty experienced by certain elements in the population in adapting themselves to the requirements of even our present crude culture.
Galton's last notable work in this field, Natural Inheritance (1889), added little to his previous ideas, but contained notable contributions to statistical method. He here developed his theory of regression and his law of ancestral inheritance. The theory of regression laid the basis for the coefficient of correlation as the means of measuring the intensity of inheritance, a device that Professor Karl Pearson, working under a scientific urge remarkably similar to Galton's, has developed with real genius. The fact of filial regression—or the tendency of offspring to vary less from the
( 280) racial or group type than the parents—and the law of ancestral inheritance—or a statement of the contribution of each grade of ancestors, parents, grandparents, etc., to the traits of an individual, are remarkable statistical anticipations of Weismann's theory of the continuity of the germ-plasm. In a mixed population where pure-line breeding is almost wholly wanting, each individual is the child of the race, or as Galton said, each individual "inherits partly from his parents, partly from his ancestry."
This phrase suggests continuity of inheritance, but does not suggest the segregation of the germ-plasm. But it should here be noted that Galten was extremely skeptical of the "Inheritance of Acquired Characters" (ibid., pp. 14-15). His anticipation of Weismann is striking:
The ovary of the mother is as old as the mother herself; it was well developed in her own embryonic state. The ova it contained in her adult life were actually or potentially present before she was born, and they grew as she grew. The same may be said with little reservation of the male elements. It is, therefore, extremely difficult to sec how acquired faculties can be inherited by the children.
Galton found the extent of the filial regression to be one-third and the law of ancestral inheritance to be that one inherits one-half of his traits equally from his immediate parents, one-fourth from his four grandparents, and so on. Pearson has calculated the degree of resemblance between parent and offspring for many traits and has modified the quantitative statement of the law of ancestral inheritance by various considerations, notably the extent of assortative mating, or the tendency of like to mate with like. It is, however, of the utmost importance to note that the quantitative statement of the law of ancestral inheritance has little significance as a statement of the contribution of each grade of ancestors, for each person is descended through segregated and crossing germ-plasms from an infinity of ancestors; but it has value as indicating the relative degrees of resemblance between any generation and the various preceding ones.
In line with his earliest work was Galton's Noteworthy Families written in conjunction with Edgar Schuster (London, 1906). This was a study of the families of one hundred of the Fellows of the Royal Society. It is obvious that mere education, wealth or social prestige would not suffice to secure the election of very many men to such honor; much less could these environmental conditions account for the reappearance in the same families through several generations of truly distinguished men. Opportunity may develop talent but it cannot create it. In an appendix is given a list of 38 Fellows with 32 distinguished fathers. It may thus be said that Galton definitely established that ability is inherited, though in this study he threw little light on the even greater question of what proportion of talent is fully developed under existing social conditions.
This extensive reference to Galton's work may seem to many unduly long but it seems warranted by his profound importance for our knowledge of the exact nature of individual differences and the relative importance of heredity and environment in producing them. Meanwhile, largely in consequence of the stimulation due to Galton, contributions to the subject were made by anthropologists, criminologists, biometricians, eugenists, psychologists and sociologists. Galton's researches served to set the essential problems and largely to solve some of them. These are: 1, How are the individual differences distributed? 2, What is the
( 281) relative weight of heredity and environment in producing them? 3, What is the significance of these differences for political and social life?
While the works of Quetelet and Galton gave a certain clearness to our ideas of how the differences are grouped about the type or average, it remained for the criminologists, anthropologists and educational psychologists to give greater quantitative precision to this grouping, the form and extent of variations from the normal, the relative frequencies of the different values of a trait and the extra-ordinary complexity of the causal factors involved. To be sure, Quetelet had done much as regards height, weight and various bodily proportions; Galton had advanced our knowledge of the variations of mental and moral qualities. Alphonse Bertillon devised a system of anthropometry for the identification of criminals, adopted in France in 1883 but subsequently generally superseded by the finger-print system developed by Galton with the aid of Sir William Herschel. Lombroso published his anthropometrical measurements of 400 criminals in 1871 and his Criminal Man in 1876, and thereafter the inquiries into the distribution of mental and moral traits became multitudinous.
(To be continued)
[Editors' Note: We have not been able to locate the
continuation of this article.]