History of Cognitive and Aptitude Screening

Lewis Terman (1917) was the first American psychologist to use “mental tests” as screening devices in the selection of law enforcement personnel. On October 31, 1916, at the request of the city manager of San Jose, California, he administered an abbreviated form of the Stanford-Binet to 30 police and fire department applicants. They ranged in age from 21 to 38, with a median age of 30. Only four had attended high school, and none had attended beyond the sophomore year. Terman found that most of the applicants functioned near the dull-normal range of intelligence (68-84 on the Stanford revision of the Binet-Simon Intelligence Scale); only three obtained an IQ over 100, the score considered average for the general population. Based on his experience with the intellectual capabilities of school-age children, Terman suggested, somewhat arbitrarily, that applicants with an IQ under 80 were not fit for police work or firefighting. The city manager agreed, and 10 applicants were immediately excluded from further consideration.

A contemporary of Terman, psychologist Louis Thurstone, was also interested in the value of intellectual testing in police screening. Thurstone (1922) administered the newly developed Army Intelligence Examination (Army Alpha) to 358 male members of the Detroit Police Department. The Army Alpha, developed by Robert Yerkes, E. L. Thorndike, and Lewis Terman and adopted by the U.S. Army in 1917, was probably the first exclusively American test of intelligence (Resnick, 1997). Police officers at all ranks scored below average on the Army Alpha; in fact, the more experienced the police officer, the lower was his intelligence score. The average score for the 307 patrol officers was 71.44; the sergeants averaged 54.71; and the 17 lieutenants, 57.80 (Army Alpha mean = 100, standard deviation of 15). Thurstone concluded that law enforcement did not attract intelligent individuals, and the more intelligent individuals who entered police service left for other occupations where their abilities and intelligence were better utilized.

Law enforcement officers were vindicated somewhat, however, when Maude A. Merrill (1927) administered the Army Alpha to a group of already employed officers and applicants. They scored at the average level (the sample’s mean IQ was 104). The differences between her findings and those of Terman and Thurstone were probably due to department leadership factors, recruitment procedures, and selection ratios (Terrio, Swanson, & Chambelin, 1977). Intelligence testing continued throughout much of the middle part of the 20th century and may still exist in some departments today. However, questions about the validity of such assessment and understandable resistance from police unions persuaded most agencies to turn to a different form of assessment, the personality assessment.

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