TWINS AND HEREDITY 489 



nearly the same, the city twin having perhaps slightly better training. 

 When examined, they were very similar in all genetic characters, but 

 the city boy was in much better physical condition, weighing over 10 

 pounds more than his brother, though they were both small persons. 

 In mental capacity the city boy was, on the basis of most of the tests 

 given, definitely superior, though they were nearly equal on the Stan- 

 ford-Binet test. In will-temperament and emotional tests they were 

 very far apart, as far apart as were Muller's twins in this respect. 

 In summary, this pair shows marked differences physically, mentally, 

 and temperamentally, but more pronounced differences in tempera- 

 ment than in either of the others. 



Newman's fourth case concerns itself with a pair of young women, 

 now twenty-nine years of age, separated at five months, and reared 

 in different families in the same part of Ohio. One was reared entirely 

 on a farm, while the other lived mostly an indoor life in a town. The 

 town girl had grade-school and high-school education, the farm girl 

 only country grade-school training. They were almost identical phys- 

 ically until about twelve years ago, but now the farm girl is in far 

 better physical condition, weighing 138 pounds as compared with no 

 pounds for the town girl, and being very much stronger and more 

 vigorous. The town girl had a mental rating much higher than her 

 sister, the difference being over three times as great as the average 

 difference of fifty pairs of identical twins reared together and consid- 

 erably greater than the average differences of fifty pairs of fraternal 

 twins reared together. In will-temperament and emotional reactions 

 they are extremely different, as far apart as were Muller's twins or 

 Newman's third case. In summary, these twins were about equally 

 different in physical, mental, and temperamental characteristics. 



A fifth case is being studied just as this revised edition goes to 

 press. It concerns itself with a pair of twin women, now thirty-eight 

 years old, separated at three months. They did not know of each 

 other's existence till they were sixteen years old. A preliminary 

 study of the data shows rather close similarity mentally and tempera- 

 mentally, but a great difference in physical condition. 



It is still too early to attempt to draw general conclusions on the 

 basis 'of these six cases, but some facts confront us that cannot be 

 dodged. Perhaps the most disconcerting fact revealed by the data is 

 that fraternal twins reared together are on the average somewhat more 

 similar in mental rating, as judged by intelligence tests, than are identical 

 twins reared apart. This seems to mean that when heredity is different 



