Temperament theory has its roots in the ancient four humours theory. It may have origins in ancient Egypt or Mesopotamia , but it was the Greek physician Hippocrates (460–370 BC) who developed it into a medical theory. Certain human moods, emotions, and behaviours were caused by an excess or lack of body fluids (called "humour"): blood , yellow bile , black bile, and phlegm . there are four fundamental personality types: sanguine , choleric , melancholic , and phlegmatic Sanguine The personality type of Sanguine is described primarily as being enthusiastic, active, and social. Sanguine tend to be more extroverted and enjoy being part of a crowd; they find that being social, outgoing, and charismatic is easy to accomplish. Individuals with this personality have a hard time doing nothing and engage in a more risk-seeking behaviour. Choleric Choleric individuals also tend to be more extroverted. They are described as being independent, decisive