HEREDITY IN MAN in 



environment (home training, etc.), to which brothers are 

 subjected, and which might produce a resemblance in- 

 dependently of inheritance. Neither of these disturbing 

 factors can, however, operate to any appreciable degree 

 in the case of the physical characteristics considered, 

 which are taken from the same schedules and filled up 

 by the same teachers, so that the similarity in results 

 strongly supports the view that the resemblance between 

 members of the same family in regard to mental character- 

 istics is actually due to inheritance. 



TABLE 6. Examples of the intensity of resemblance 

 between brothers for various characteristics. 



Characteristic. 



Correlation. 



A. PHYSICAL. 



Colour of eyes (light, medium, dark), -5 



Hair (smooth, wavy or curly), 



Breadth of Head, 



B. MENTAL. 



Vivacity (quiet or noisy), 

 Assertiveness (shy or self-assertive), 

 Popularity (popular or unpopular), 

 Conscientiousness (keen or dull), 

 Intelligence (six categories), 



'5 

 6 



5 

 5 



5 

 6 



5 



The figures which we have discussed in this chapter 

 form only a small selection from the mass of data dealing 

 with a wide range of characteristics, mental and physical, 

 including the power of resistance to disease, which has 

 been collected by Pearson and his colleagues. \Yhile 

 they do not help us much to understand the physiology 

 of inheritance, in the way for instance that Mendel's 



