Hiring managers can determine the intelligence of a candidate within minutes of an interview: No general intelligence test or degree is necessary
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The evidence is overwhelming. Take tank gunners. You wouldn't think intelligence would have much effect on the ability to shoot straight, but apparently it does. Replacing a gunner who'd scored Category IV on the aptitude test (ranking in the 10-30 percentile) with one who'd scored Category IIIA (50-64 percentile) improved the chances of hitting targets by 34 percent. (For more on the meaning of the test scores, click here.)
In another study cited by the RAND report, 84 three-man teams from the Army's active-duty signal battalions were given the task of making a communications system operational. Teams consisting of Category IIIA personnel had a 67 percent chance of succeeding. Those consisting of Category IIIB (who'd ranked in the 31-49 percentile on the aptitude test) had a 47 percent chance. Those with Category IV personnel had only a 29 percent chance.
The same study of signal battalions took soldiers who had just taken advanced individual training courses and asked them to troubleshoot a faulty piece of communications gear. They passed if they were able to identify at least two technical problems. Smarts trumped training. Among those who had scored Category I on the aptitude test (in the 93-99 percentile), 97 percent passed. Among those who'd scored Category II (in the 65-92 percentile), 78 percent passed. Category IIIA: 60 percent passed. Category IIIB: 43 percent passed. Category IV: a mere 25 percent passed.
The pattern is clear: The higher the score on the aptitude test, the better the performance in the field. This is true for individual soldiers and for units. Moreover, the study showed that adding one high-scoring soldier to a three-man signals team boosted its chance of success by 8 percent (meaning that adding one low-scoring soldier boosts its chance of failure by a similar margin).
Smarter also turns out to be cheaper. One study examined how many Patriot missiles various Army air-defense units had to fire in order to destroy 10 targets. Units with Category I personnel had to fire 20 missiles. Those with Category II had to fire 21 missiles. Category IIIA: 22. Category IIIB: 23. Category IV: 24 missiles. In other words, to perform the same task, Category IV units chewed up 20 percent more hardware than Category I units. For this particular task, since each Patriot missile costs about $2 million, they also chewed up $8 million more of the Army's procurement budget.