Final answer:
According to Galen's Humoral Theory, an excess of black bile causes a person to have a melancholic temperament, leading them to be reserved, anxious, and unhappy.
Step-by-step explanation:
According to Galens Humoral Theory of Personality, an excess of black bile is thought to cause a person to exhibit a melancholic temperament, which is characterized by the person being reserved, anxious, and unhappy. This theory, which was built upon Hippocrates's earlier work on bodily humors and their link to personality, was a prevailing approach to understanding human behavior and personality differences for more than a millennium, predominantly during the Middle Ages. The melancholic temperament is one of the four distinct temperaments identified by Galen, with the others being choleric, sanguine, and phlegmatic, each associated with different bodily humors and personality traits.