INFLUENCES OF ENVIRONMENT 125 



vestigalions of J>oas and Wissler "^ that imfavorable 

 environnieiital influences which cause a child to grow 

 slowly during a number of years act as retarding causes 

 such that the child will probably continue to grow more 

 slowly than other, nomial children. Even at completed 

 growth the child is smaller than its normal companions. 

 On the other hand, children who have had their growth 

 accelerated by favorable surroundings reach the adult 

 stage earlier and attain a relatively greater size and de- 

 velopment. Thus the absolute size and the relative pro- 

 ])ortions of the body are influenced by periods of retarda- 

 tion or acceleration. . These periods of change in the rate 

 of growth appear to be due to such retarding causes as: 

 i]lness"in early childhood, malnutrition, lack of fresh air 

 and physical exercise, — to the influences of environment, 

 physical and socials 



The conclusion to be drawn from this body of evidence 

 is that^nvironment is most potent as a modifying cause 

 in early plastic years. On the other hand, there are now 

 available several studies of considerable importance 

 which seem to show that environment is not such an im- 

 portant factor in the development of children. These in- 

 vestigations have been made by the Galton Laboratory 

 for National Eugenics of the L^niversity of London, un- 

 der the direction of Professor Karl Pearson. The in- 

 heritance of vision and the relative influence of heredity 

 and environment on sight have been studied ^ and the 

 statisticians have reached the following conclusions from 

 their admittedly slender data: (1) No evidence whatever 

 that over-crowded, poverty-stricken homes, or physically 



8 Boas, F., and Wissler, C.—fitatistics of Oroicth, Report of U. S. Com- 

 vufifiioner of Education for JHOJf, pp. 25- 132. 

 * Eugenics Laboratory Memoirs, V. 



