BIOLOGY IN HUMAN" AFFAIRS 



neither very dull nor very bright. Above an upper critical 

 point on the intelligence scale, as well as below a lower 

 critical score, the proportion of girls who disappear from 

 the payroll is greater than it is within the middle zone of 

 mental alertness. Many other variables, such as wage rate, 

 also are associated with permanency of employment, so 

 that this characteristic relationship between brightness 

 and stability on a relatively routine job is far from close, 

 but it is striking enough to be significant. Since this fact 

 was first definitely established by Yoakum and Bills some 

 ten years ago, it has been kept in mind by all who use 

 measures of mental alertness as one of the aids to selection 

 of office workers. The hypothesis was not new in 1920, 

 but its verification was possible only after reliable ways of 

 measuring mental alertness had been developed. 



A clean-cut demonstration of an upper critical score 

 for success in a selling occupation was made at Carnegie 

 Institute of Technology in 1919. Three years previously a 

 group of twenty-seven companies maintaining national 

 sales organizations established the Bureau of Salesmanship 

 Research, later the Bureau of Personnel Research. This 

 bureau was to pool the experience of the cooperating 

 members, to evaluate their current procedures, and to 

 experiment with new ways of selecting and developing 

 salesmen. The first year's work, under Walter Dill Scott, 

 resulted in a manual of "Aids in Selecting Salesmen," con- 

 taining an improved personal history record or application 

 form, a model letter of reference to former employers, a 

 guide to interviewing which helped the interviewer to 

 focus his attention on essential traits and to record his 

 judgments quantitatively, and a set of five psychological 

 tests with directions for administering them. Among 

 these tests was a group intelligence examination, a fore- 

 runner of Army Alpha. It was given to various groups of 

 salesmen and sales applicants, and their scores were then 



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