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V.

THE first argument in favor of the view that the capacity for intelligence is hereditary is an argument by analogy. There is a good deal of evidence that idiocy and certain forms of degeneracy are transmitted from parents to offspring. There are, for example, a number of notorious families -- the Kallikaks, the Jukes, the Hill Folk, the Nams, the Zeros and the Ishmaelites, who have a long and persistent record of degeneracy. Whether these bad family histories are the result of a bad social start or of defective germplasm is not entirely clear, but the weight of evidence is in favor of the view that there is a taint in the blood. Yet even in these sensational cases, in fact just because they are so sensational and exceptional, it is important to remember that the proof is not conclusive.

There is, for example, some doubt as to the Kallikaks. It will be recalled that during the Revolutionary War a young soldier, known under the pseudonym of Martin Kallikak had an illegitimate feeble-minded son by a feeble-minded girl. The descendants of this union have been criminals and degenerates. But after the war was over Martin married respectably. The descendants of this union have been successful people. This is a powerful evidence, but it would, as Professor Cattell (1) points out, be more powerful, and more interesting scientifically, if the wife of the respectable marriage had been feeble-minded, and the girl in the tavern had been a healthy, normal person. Then only would it have been possible to say with complete confidence that this was a pure case of biological rather than of social heredity.

Assuming, however, that the inheritance of degeneracy is established, we may turn to the other end of the scale. Here we find studies of the persistence of talent in superior families. Sir Francis Gallon, for example, found "that the son of a distinguished judge had about one chance in four of becoming himself distinguished, while the son of a man picked out at random from the general population had only about one chance in four thousand of becoming similarly distinguished." (2) Professor Cattell in a study of the families of one thousand leading American scientists remarks in this connection: "Galton finds in the judges of England a notable proof of hereditary genius. It would be found to be much less in the judges of the United States. It could probably be shown by the same methods to be even stronger in the families conducting the leading publishing and banking houses of England and Germany." And in another place he remarks that "my data show that a boy born in Massachusetts or Connecticut has been fifty times as likely to become a scientific man as a boy born along the Southeastern seaboard from Georgia to Louisiana."

It is not necessary for our purpose to come to any conclusion as to the inheritance of capacity. The evidence is altogether insufficient for any conclusion, and the only possible attitude is an open mind. We are, moreover, not concerned with the question of whether intelligence is hereditary. We are concerned only with the claim of the intelligence tester that he reveals and measures hereditary intelligence. These are quite separate propositions, but they are constantly confused by the testers. For these gentlemen seem to think that if Gallon's conclusion about judges and the tale of the Kallikaks are accepted, then two things follow: first, that by analogy (3) all the graduations of intelligence are fixed in heredity, and second that the tests measure these different grades of heredity intelligence. Neither conclusion follows necessarily. The facts of heredity cannot be proved by analogy; the facts of heredity are what they are. The question of whether the intelligence test measures heredity is a wholly different matter. It is the only question which concerns us here.

We may start then with the admitted fact that children of favored classes test higher on the whole that other children. Binet tests made in Paris, Berlin, Brussels, Breslau, Rome, Petrograd, Moscow, in England and in America agree on this point. In California Professor Terman (4) divided 492 children into five social classes and obtained the following correlation between the median intelligence quotient and social status:

On the face of it this table would seem to indicate, if it indicates anything, a considerable connection between intelligence and environment. Mr. Terman denies this, and argues that "if home environment really has any considerable effect upon the IQ we should expect this effect to become more marked, the longer the influence has continued. That is, the correlation of IQ with social status should increase with age." But since his data show that at three age levels (5-8 years) and (9-11 years) and (12-15 years) the coefficient of correlation with social status declines (it is .43, .41 and .29 respectively), Mr. Terman concludes that "in the main, native qualities of intellect and character, rather than chance (sic) determine the social class to which a family belongs." He even pleads with us to accept this conclusion: "After all does not common observation teach us that etc. etc." and "from what is already known about heredity should we not naturally expect" and so forth and so forth.

Now I propose to put aside entirely all that Mr. Terman's common observation and natural expectations teach him. I should like only to examine his argument that if home environment counted much its effect ought to become more and more marked as the child grew older.

It is difficult to see why Mr. Terman should expect this to happen. To the infant the home environment is the whole environment. When the child goes to school the influences of the home are merged in the larger environment of school and playground. Gradually the child's environment expands until it takes in a city, and the larger invisible environment of books and talk and movies and newspapers. Surely Mr. Terman is making a very strange assumption when he argues that as the child spends less and less time at home the influence of home environment ought to become more and more marked. His figures, showing that the correlation between social status and intelligence declines from .43 before eight years of age to .29 at twelve years of age, are hardly an argument for hereditary differences in the endowment of social classes. They are a rather strong argument on the contrary for the traditional American theory that the public school is an agency for equalizing the opportunities of the privileged and the unprivileged.

But Mr. Terman could by a shrewder use of his own data have made a better case. It was not necessary for him to use an argument which comes down to saying that the less contact the child has with the home the more influential the home ought to be. That is simply the gross logical fallacy of expecting increasing effects from a diminishing cause. Mr. Terman would have made a more interesting point if he had asked why the influence of social status on intelligence persists so long after the parents and the home have usually ceased to play a significant part in the child's intellectual development. Instead of being surprised that the correlation has declined from .43 at eight to .29 at twelve, he should have asked why there is any correlation left at twelve. That would have posed a question which the traditional eulogist of the little red schoolhouse could not answer offhand. If the question had been put that way, no one could dogmatically have denied that differences of heredity in social classes may be a contributing factor. But curiously, it is the mental tester himself who incidentally furnishes the most powerful defence of the orthodox belief that in the mass differences of ability are the result of education rather than of heredity.

The intelligence tester has found that the rate of mental growth declines as the child matures. It is faster in infancy than in adolescence, and the adult intelligence is supposed to be fully developed somewhere between sixteen and nineteen years of age. The growth of intelligence slows up gradually until it stops entirely. I do not know whether this is true or not, but the intelligence testers believe it. From this belief it follows that there is "a decreasing significance of a given amount of retardation in the upper years." (5) Bluet, in fact, suggested the rough rule that under ten years of age a retardation of two years usually means feeble-mindedness, while for older children feeblemindedness is not indicated unless there is a retardation of at least three years.

This being the case the earlier the influence the more potent it would be, the later the influence the less significant. The influences which bore upon , the child when his intelligence was making its greatest growth would leave a profounder impression than those which bore upon him when his growth was more nearly completed. Now in early childhood you have both the period of the greatest growth and the most inclusive and direct influence of the home environment. Is it surprising that the effects of superior and inferior environments persist, though in diminishing degree, as the child emerges from the home?

It is possible, of course, to deny that the early environment has any important influence on the growth of intelligence. Men like Stoddard and McDougall do deny it, and so does Mr. Terman. But on the basis of the mental tests they have no right to an opinion. Mr. Terman's observations begin at four years of age. He publishes no data on infancy and he is, therefore, generalizing about the hereditary factor after four years of immensely significant development have already taken place. On his own showing as to the high importance of the earlier years, he is hardly justified in ignoring them. He cannot simply lump together the net result of natural endowment and infantile education and ascribe it to the germplasm.

In doing just that he is obeying the will to believe, not the methods of science. How far he is carried may be judged from this instance which Mr. Terman cites (6) as showing the negligible influence of environment. He tested twenty children in an orphanage and found only three who were fully normal. "The orphanage in question," he then remarks, "is a reasonably good one and affords an environment which is about as stimulating to normal mental development as average home life among the middle classes." Think of it. Mr. Terman first discovers what a "normal mental development" is by testing children who have grown up in an adult environment of parents, aunts and uncles. He then applies this footrule to children who are growing up in the abnormal environment of an institution and finds that they are not normal. He then puts the blame for abnormality on the germplasm of the orphans.

WALTER LIPPMANN.

(To be continued.)