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THOMAS A. LEWIS 
ways essential ability consists in the power to combine 
continuous attention with an impulse to quick reaction, and 
with a certain imagination by which the movements of pedes- 
trians and vehicles are foreseen/’ he contrived a device whereby 
it was possible to test a man for these specific characteristics. 
There was a crank which the subject turned, and red and black 
puppet figures that appeared on a passing screen in different 
combinations, and the noting of certain particular combinations 
seemed to be the thing that told the tale. The number of the 
mistakes made in this particular and the rapidity in turning the 
crank were measured. ‘‘Experienced motormen felt, in carry- 
ing out this experiment,” says Muensterberg, “that the mental 
attitude was indeed quite similar to that of their function on the 
street.” He remarks upon the fact that “13 per cent of the 
gross receipts of some roads go for damages due to avoidable 
accidents,” and significantly adds that his “experiments resulted 
in the rejection of one-fourth of the applicants for positions as 
motormen.” 
Other men engaged in psychological research have also become 
greatly interested in recent years in the practical possibilities of 
the science, and in some institutions of higher education (Car- 
negie Institute of Technology, for example) applied psychology 
has assumed large proportions. 
But it is the service performed in connection with the organi- 
zation of our recent Army that vocational psychology stands out. 
Psychology here undertook a task of mental engineering which 
was on a scale so vast as to require of the specialists in that 
field the abandonment for the duration of the war of many or 
all of their other duties. The classification of the membership 
of the Army on the basis of trade abilities and general intelli- 
gence and officer qualities was largely the psychologist’s respon- 
sibility. The dual problem (set by Muensterberg) of studying 
the man and the occupation as the prime fundamental in voca- 
tional guidance, was attacked in great earnestness, and with the 
result that it became possible to select officers with some assur- 
ance that right selections were being made, to classify recruits 
according to their capacities both to learn what a soldier must 
