Havelock Ellis, who likewise studied British men of genius, throws additional light on the subject. "Painters and sculptors," he found, "constitute a group which appears to be of very distinct interest from the point of view of occupational heredity. In social origin, it may be noted, the group differs strikingly in constitution from the general body of men of genius in which the upper class is almost or quite predominant. Of 63 painters and sculptors of definitely known origin, only two can be placed in the aristocratic division. Of the remainder 7 are the sons of artists, 22 the sons of craftsmen, leaving only 32 for all other occupations, which are mainly of lower middle class character, and in many cases trades that are very closely allied to crafts. Even, however, when we omit the trades as well as the cases in which the fathers were artists, we find a very notable predominance of craftsmen in the parentage of painters, to such an extent indeed that while craftsmen only constitute 9.2% among the fathers of our eminent persons generally, they constitute nearly 35% among the fathers of the painters and sculptors. It is difficult to avoid the conclusion that there is a real connection between the father's aptitude for craftsmanship and the son's aptitude for art.
"To suppose that environment adequately accounts for this relationship is an inadmissible theory. The association between the craft of builder, carpenter, tanner, jeweller, watchmaker, woodcarver, ropemaker, etc., and the painter's art is small at best, and in most cases is non-existent."
Arreat, investigating the heredity of 200 eminent European painters, reached results similar to those of Ellis, according to the latter's citation.
Arithmetical ability seems similarly to be subdivided, according to Miss Cobb.[42] She made measurements of the efficiency with which children and their parents could do problems in addition, subtraction, multiplication and division, and could copy a column of figures. "The measurements made," she writes, "show that if, for instance, a child is much quicker than the average in subtraction, but not in addition, multiplication or division, it is to be expected that one at least of his parents shows a like trait; or if he falls below the average in subtraction and multiplication, and exceeds it in addition and division, again the same will hold true of at least one of his parents." These various kinds of arithmetic appear to be due to different functions of the brain, and are therefore probably inherited independently, if they are inherited at all.
To assume that the resemblance between parent and offspring in arithmetical ability is due to association, training and imitation is not plausible. If this were the case, a class of children ought to come to resemble their teacher, but they do not. Moreover, the child sometimes resembles more closely the parent with whom he has been less associated in daily life.
From such data as these, we conclude that mental inheritance is considerably specialized. This conclusion is in accord with Burris' finding (cited by Thorndike) that the ability to do well in some one high school study is nearly or quite as much due to ancestry as is the ability to do well in the course as a whole.
To sum up, we have reason to believe not only that one's mental character is due largely to heredity, but that the details of it may be equally due to heredity, in the sense that for any particular trait or complex in the child there is likely to be found a similar trait or complex in the ancestry. Such a conclusion should not be pushed to the point of assuming inheritance of all sorts of dispositions that might be due to early training; on the other hand, a survey of the whole field would probably justify us in concluding that any given trait is more likely than not to be inherited. The effect of training in the formation of the child's mental character is certainly much less than is popularly supposed; and even for the traits that are most due to training, it must never be forgotten that there are inherited mental bases.
If the reader has accepted the facts presented in this chapter, and our inferences from the facts, he will admit that mental differences between men are at bottom due to heredity, just as physical differences are; that they are apparently inherited in the same manner and in approximately the same degree.