XXI 



WHAT PSYCHOLOGY CONTRIBUTED TO THE WAR 

 ROBERT M. YERKES 



WITH the preceding chapter on methods as an introduc- 

 tion, an attempt will be made in the present chapter to 

 state very briefly what psychology accomplished during the 

 war. It is impossible to give a complete account of the work, 

 but results and practical applications may be sampled in such 

 a way as to give the reader a fair idea of the nature and sig- 

 nificance of this new kind of military service. 



- - Entitled Men ( 13792 } -Relatively Illiterate 



Enlisted Men (82936) Literals 



..-^--- Corporsh (4023) 



i i Sergeant* (3393) 



O.T.C (9240) 



Officers (8819) 



0- D C.- C C + B A 



Fio. 1. DISTRIBUTION or INTELLIGENCE RATINGS IN TYPICAL ARMT GROUPS, 

 BHOWINO VALUE OF TESTS IN IDENTIFICATION OF OFFICER MATERIAL. ILLITERATE 

 GROUP GIVEN BETA; OTHER GROUPS, ALPHA. 



Figure i. Distribution of intelligence grades for typical army groups. 



The first thing which appeared in the results of the psycho- 

 logical examination of soldiers was remarkable difference in 

 the intelligence of individuals and of army groups. This fact 

 was no surprise to psychologists, but it created a profoundly 

 important impression in the minds of military officers who were 

 relatively unfamiliar with methods and results of mental 

 measurement. The two figures, i and 2, will suffice to indicate 



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