126 



TEE POPULAR SCIENCE MONTHLY 



also due in part to differences in environment, circumstances, training 

 — one sort of home-life being more favorable than another to progress 

 through school, for example. Each advance in the study of individual 



10 20 30 4-0 50 60 70 80 



E.XQTnple5 done correctly in 15 minutes. 



Chart 1. The Rei^tivt! Frequencies of Different Degrees of Ability in 

 Addition in the Case of Fourth-grade Pupils. 



differences, however, shows that differences in maturity and differences 

 in the circumstances of nurture account for only a small fraction of the 

 differences actually found in individuals of the same general environ- 

 ment of an American city in 1900-1912. Long before a child begins 



I 1 = I percent 



1 

 so 



10 ^0 30 40 



Gain made in examples done correctly in 10 minules 

 Chart 2. The Relati\-b Frequencies of Different Amounts of Gain from 

 Fifty Minutes of Practise in Division, in the Case of 

 Pupils op the Same School Grade. 



his schooling, or a man his work at trade or profession, or a woman lier 

 management of a home — long indeed before they are born — their super- 

 iority or inferiority to others of thp same environmental advantages is 

 determined by the constitution of the germs and ova whence they spring, 

 and which, at the start of their individual lives, they arc. 



Of the score or more of important studies of the causes of individual 



