28 THE RELATIVE STRENGTH OF NURTURE AND NATURE 



Hence the relation between goodness of vision and home environment for 

 a constant age = -073, or, the relationship between home environment, as 

 measured by cleanliness of body and clothing, and goodness of vision is just 

 about one-seventh of the intensity of the relationship between goodness of vision 

 in parent and child. Nor are we sure that the home environment is the source 

 of this small correlation ; for not only do the statistics indicate a marked 

 selection of the ages and the homes, but degeneracy in the parents, which is 

 usually characterised by defective vision among other factors, may be the source 

 of the want of cleanliness ; and the association of this with bad vision be thus 

 (inly a secondary hereditary effect. Until we know far better than we do at 

 present the closeness of correlation between various physical degeneracies and 

 the relation of these in the parent to the home environment, it seems hardly 

 possible to determine whether these small correlations are really the expression 

 of nurture, or only a secondary effect of nature. What is certain is that they 

 are practically negligible compared with the direct effect of nature. 



K. P. 



