524 INHERITANCE OF MENTAL TRAITS 



average quotient of 85 or lower. It should be empha- 

 sized, however, that the figures refer to averages. In 

 both cases the range of quotients is wide and each dis- 

 tribution curve greatly overlaps the other. 



.\lthough feeble-minded children are occasionally 

 found in socially successful famiUes, they are several 

 times as frequent in the families of low occupational and 

 social status; and although gifted children are sometimes 

 found in the families of unskilled laborers, they are many 

 times as frequent in families belonging to the profes- 

 sional classes. 



Of several hundred California children who were found 

 to have an intelligence quotient of 140 or higher, and all 



©B®© 



Fig. 1.52. — Inheritance of "insanity." From the central mating of 

 two nonnal ix^rsoas there are derived 8 children, 3 insane. liut there 

 i.s the hereditary tendency in the genu plasm of both parents. Mott, 

 1905. 



of whom probably ranked within the top half of the top 

 1 per cent of the general school population, approxi- 

 mately 50 per cent harl fathers who belonged to one or 

 another of the professions. More than 35 per cent were 

 from the semi-professional or mercantile classes, some- 

 thing over 10 per cent from the skilled labor classes, and 

 less than 5 per cent from the unskilled and semi-skilled 

 occupational classes combined. Galton, Ellis, and others 

 have brought out similar facts regarding the social origin 

 of men of genius. 



Such facts are of great significance. They mean that 

 we must usually look to the higher social classes to pro- 



