332 THE POPULAR SCIENCE MONTHLY
a certain objective standard of distinction and 3,296 failed to do so. The environmental influences must have been mostly distributed at random throughout the group. Yet this did not cause any random distribution of the distinguished persons. Fifteen out of the sixteen were closely related to other distinguished persons.
The second group of royalty contained all the close connections of twenty-three reigning historical dynasties. This group was obtained by a different method, but in part overlaps the other group. Here detailed analysis was made not only of the question of intellectual distinction but of mental and moral variations. Environment was shown to be of little or no consequence in the production of important differences. 44
The third research to appear on the problem of nature versus nurture is that of E. L. Thorndike, 45 on the origin of mental differ- ences among children attending the public schools in the city of New York. Thorndike, like Galton, used the records of twins to support his argument, but went into the matter with far greater scientific analysis and published all the details of his measurements. He presents :
(1) The results of precise measurements of fifty pairs of twins from 9 to 15 years old in [eight physical and] six mental traits and (2) their bearing upon the comparative importance of heredity and environment as causes of human differences in intellectual achievement. They will be found to give well- nigh conclusive evidence that the mental likenesses found in the case of twins and the differences found in the case of non-fraternal pairs, when the individuals compared belong to the same age, locality and educational system, are due, to at least nine-tenths of their amount, to original nature.
In concluding his research Thorndike says :
It shows such likeness and differences in environment as act upon children living in New York City and attending its public schools are utterly inadequate to explain the likenesses and differences found in the traits measured, and are in all probability inadequate to explain more than a small fraction of them. The arguments concerned the lack of differences in the amount of resemblance (1) between young and old twins, (2) between traits little and traits much subject to training and (3) between mental and physical traits, and also the great increase in resemblances of twins over ordinary siblings [brothers and sisters].
Thorndike's research appears to be very conclusive and confirmatory as far as it goes. Of course one might contend that after all the
44 For the arguments which support this belief see Popular Science Monthly, August, 1902-April, 1903 (Vol. LXL, pp. 375, 453, 455, 457. 507. 508; Vol. LXIL, pp. 84, 208, 423, 426, 497. 500-503). Same in reprinted form, pp. 9, 17, 19, 21, 2G, 27, 41. 65, 73. 76, 79, 82-85. Additional arguments of a generalized nature may be found in " Mental and Moral Heredity in Royalty : a Statistical Study in History and Psychology," New York, Henry Holt, 1906. pp. 276-298. The arguments drawn from intensive analysis of small groups may be found on pp. 6, 56, 81, 119, 123, 170, 222, 224, 231, 246-247, 248-249. 253-254, 271.
""Measurements of Twins," Arch, of Philosophy, Psychology and Scientific Methods, New York. The Science Press, 1905, pp. 64.