NURTURE AND NATURE 21 



The eyesight results are already published in a memoir by 

 Amy Barrington and Karl Pearson. Normal vision is on the whole 

 slightly associated with overcrowding, bad economic conditions and 

 morally defective parentage. Can it be that these home conditions 

 keep the children in the streets, and so relatively away from bad 

 environment and in relatively fresher air? Whatever may be the 

 cause the Edinburgh statistics show that the effect of home influence 

 is not one-tenth that of heredity, and what exists, if it be appreciable 

 at all, is in the opposite direction from what we should have antici- 

 pated. Intelligence is slightly associated with few people per room 

 and with a good economic condition in the home for boys and girls, 

 though for boys it is scarcely appreciable; it is also associated for 

 girls very slightly with good physical and moral condition in the 

 parents, but for boys we get better intelligence in the children 

 associated with bad physical and moral condition in the parents. 



Glands and hearing tell the same tale. There is only a slight 

 connection between the presence of swollen glands or bad hearing and 

 bad environmental conditions. All the coefficients are small and 

 irregular, some scarcely appreciable, but in most cases they are 

 positive, i.e. better physique goes with better environment, though 

 it is but in a weak degree 1 . 



Such a table as that on p. 20, indicating in many directions the 

 relative insignificance of nurture in influencing man's welfare, gives 

 us reason to pause when we consider the methods of modern social 

 reform. 



The question of the respective influences of heredity and environ- 

 ment is becoming one of vital importance. It seems only too true at 

 the present time that the physically and mentally weaker stocks are 

 reproducing themselves at a greater rate than those of sounder 

 physique and intelligence. 



This, unchanged, must mean that the average physique and ability 

 of our nation as a whole will decline and must decline unless we can 

 prove that by a better environment we can raise the level of the 

 community. So far as our investigations have gone at present they 

 show clearly the small influence of environment ; work of the mother, 



1 Heredity as before plays far the larger part. The measure of the inheritance 

 of eyesight is equal to that found for other physical characters and the same is true 

 of intelligence (-49)- Recent work of the Laboratory (British Medical Journal, July 20, 

 1909 : see Appendix to this Lecture) shows that environmental conditions can hardly 

 be the chief source of eye-disease. The correlations are low and more often negative 

 than in the case of ear-disease. 



