BIOLOGY IN- HUMAN AFFAIRS 



academic confines of a specialty or the narrow loyalties of a 

 "pure" science — an ideal still cherished in early experi- 

 mental days — and launch out upon the world of human 

 relations and practical enterprises. Psychology must 

 "work" and be put to work. 



Distinctive in this development is the story of mental 

 testing — distinctive because it arises from so central a 

 problem as the nature of intelligence and was guided by so 

 practical an aim as to provide a measuring scale applicable 

 to a great variety of uses. It arose from the desirability of 

 detecting the subnormal children, incapable of following 

 the program of the schools fitted to normal requirements. 

 It has come to be an instrument employed in education, in 

 psychiatry, in the case histories of the dependent and 

 delinquent classes, and in industrial occupations. Intelli- 

 gence is a flexible term; it has its basis in the general level 

 of development, the neuronic adequacy and finer organi- 

 zation of the higher brain centers, and in the development 

 of these highly specialized structures. We are not musical 

 and mechanical and acrobatic and graceful and socially 

 adaptable and apt at analysis and deep reflection, by virtue 

 of quite the same patterns of development, the same supply 

 and organization of engrams. And that basic fact itself 

 gives rise to an engaging division of modern psychology 

 of which Sir Francis Galton is the founder— "The Psy- 

 chology of Individual Differences."^ 



Human variability, like the prolongation of human 

 infancy to which John Fiske first directed attention, is an 

 asset of inestimable value. Upon it the diversities of 

 employments composing modern civilization have been 

 developed. It is the trend of civilization to make the finer 

 differences count. The guiding principle is that we all grow 

 mentally, and perform more or less successfully, by virtue 



1 Surveyed in a volume under that title by R. S. Ellis, D. Appleton & Com- 

 pany, New York, 1928. 



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