Many of the most current personality tests are built on older theories—sometimes much older theories. Around 2400 years ago, the physician Hippocrates described his idea that human moods were caused by an excess or lack of basic body fluids. Too much blood and you became giddy and talkative, too little and you would become morose. Feeling lazy? Blame it on too much phlegm. He probably borrowed this ideas from someone before him whose name we no longer know.

Although this was not a sound medical observation, the idea of four different temperaments caught on and has hung on for millennia. The word temperament comes  from the same word as tempera paint and means to mix. So philosophers, physicians and psychologist kept mixing four different factors to obtain their palette of personalities.

According to the ancients Greeks these were:

• Choleric—ambitious, energetic, aggressive, even tyrannical.
• Sanguine—charismatic, impulsive, pleasure loving and self-indulgent.
• Phlegmatic—observant…