Psychometric testing is a multibillion-dollar enterprise, but has the predictive power of these tests grown with their popularity?
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Hippocrates did it first: More than 2,000 years ago, the Greek physician theorized that four bodily fluids—blood, phlegm, black bile, and yellow bile—affect human traits and behaviors. He described four fundamental temperaments: sanguine (optimistic leader-like), choleric (bad-tempered or irritable), melancholic (analytical and quiet), and phlegmatic (re
