PROBLEM OF NURTURE AND NATURE 39 



Our only reply can be that these correlations certainly do, and 

 that as long as the President of the Eugenics Education Society fails 

 to grasp their meaning, he is doing grave harm to the science of 

 eugenics, and to the studies which Francis Galton had at heart. 



One of the chief achievements of Francis Galton was his introduc- 

 tion of the conception of correlation to measure the relative intensity 

 of those very factors of social progress, which the President of the 

 Eugenics Education Society holds to be beyond comparison. Corre- 

 lation measures for us the extent to which one variate is determined 

 by a second; when correlation is high then we approach causation. 

 When we say that the correlation of the character of the offspring 

 with ancestral characters is ten times as intense as it is with environ- 

 mental factors, then we mean that the degree of dependence of the 

 child on the characters of its parentage is ten times as intense as its 

 degree of dependence on the character of its home or uprearing. 



Now if the reader will examine the accompanying tables which 

 were published in a lecture of igio 1 he will be at once struck by the 

 wholly different order of the correlations due to Nature and those due 

 to Nurture; we have an average Nurture correlation of about -03 as 

 against a Nature correlation in the closest relationships of about -50. 

 The number of these correlations have been very largely extended 

 since that date and the diagram on p. 42 shows the distribution 

 of frequency for a long series of Nurture and Nature values. It will 

 be seen at once that the two frequency distributions have no common 

 range. There is no real comparison possible between them, and 

 whereas ancestry always draws the offspring in its own direction, a 

 good environment may actually be associated with inferior physique 

 or mentality in the child. 



At this point, however, fresh criticisms of our work have been 

 advanced, also by members of the same Eugenics Education Society. 

 We admit, they say, that the environmental correlations may be of 

 the order -03 or -05 and the inheritance correlations of the order -50. 

 But this is the correlation of one character with environment. You 

 ought to take ten or twenty, and then you will have multiplied up 

 environment to be more effective than heredity for -03 x 20= -60. In 

 the first place we may suggest that it would be just as reasonable, 

 if the argument were a valid one to multiply up the favourable 

 hereditary characters, to take weight, height, muscular activity, 



1 Nature and Nurture, The Problem of the Future, Eugenics Laboratory Lecture 

 Series, No. VI, Cambridge University Press. 



