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. 



